14 ms·

Linux founder tells Intel to stop inventing magic instructions and fix problems

287 points by rsecora 6y ago

0xFFC 6y ago
Torvalds clearly does not understand the brutality of business. Intel does not care at all about customers it have at the moment. Because they have them by the balls. After many years of struggle only Apple (with its unlimited resource) was able to switch to ARM. So they don’t care. They only care about long term market, which is HPC and ML workloads. Because Nvidia is destroying anybody in that market. Look at their stock. I’ve got a news for Torvalds, it going to get bad for Intel.
- cameldrv 6y ago
  If there were ever a time where Intel had its customers by the balls the least in the past twenty years, it's now. AMD is extremely competitive in the server and desktop space, ARM/Apple is becoming competitive in the laptop space, Intel has no product in the phone/tablet space, and they are noncompetitive in the HPC/DL accelerator space. If there's anything that has typified Intel in the past decade it's a generalized failure to execute. There's been very little innovation in the core product since Haswell in 2013.
  - DubiousPusher 6y ago
    Yeah for anyone who was a computer enthusiast in the 90s and 00s the rise of ARM has been an astonishing development comparable to the ubiquity of Linux and decline of Windows.
    - Koshkin 6y ago
      > ubiquity of Linux and decline of Windows Should I read this as sarcasm?
      - ardy42 6y ago
        >> ubiquity of Linux and decline of Windows > Should I read this as sarcasm? It could only be sarcastic if he's referring to "Linux on the desktop." I don't have any numbers, but I wouldn't be surprised if he was correct about servers.
        DubiousPusher 6y ago
        Correct. I am referring to everything except desktop computing. I can see how this would be confusing as I was just referencing desktop prossesor market patterns of the 90s/00s. But I do think Windows's position in the desktop space is somewhat unsustainable at this point. I personally prefer Windows but I just don't see how a heterogenous user interface experience (with users on iOS and Android for mobile and Windows for desktop) will abide for long. I think it's only a matter of time before mobile OSes make some serious inroads to desktop. Though I suppose Google has been salivating at that thought for neaely a decade.
        cameldrv 6y ago
        If you look at the overall "computing devices with a reasonably high performance CPU" market, Linux has won the server market, and through Android, won the phone/tablet market. If you squint a bit, you can lump MacOS and iOS in this in that they have a Unix core and use a lot of the same software stack as Linux. 50 years ago, IBM owned the computing market with mainframes. They still dominate the mainframe market, that's just become a smaller and smaller portion of the overall computing market as time has gone on.
      - macintux 6y ago
        In both the server and especially mobile space Windows has lost its mojo and Linux has been a beneficiary.
      - RodgerTheGreat 6y ago
        Linux is ubiquitous. It runs on embedded devices, cell phones, and tablets which surround us. Linux runs most of the computers which underpin websites and services we interact with daily, and it is the only serious choice for HPC. A few people even run it on their laptops. Windows has declined. It is still used extensively, but Microsoft no longer dictates the browser market. Microsoft Office is commonplace, but has genuine marketshare competition in alternatives like Google Docs. Developers increasingly build "desktop" applications as web-based or multiplatform-first instead of Windows-exclusive, with the notable exception of AAA games. The Linux subsystem for Windows is a direct admission by Microsoft that developers want to work with Linux-based software for many tasks.
  - trekrich 6y ago
    Then its only a matter of time before they go bankrupt.
    - rorykoehler 6y ago
      They have the cash to get out of this if they make the right moves.
      - mindcrime 6y ago
        Exactly. A single well-time and well-executed acquisition could change the whole game. Of course we all know that executing acquisitions well is easier said than done, and I don't have a specific target in mind when I say this. It's more of an "in principle" speculation than a concrete suggestion at the moment.
        rorykoehler 6y ago
        Softbank are looking to sell some or all of their ARM holdings.
    - dathinab 6y ago
      Very unlikely. Just because they are no longer "without alternatives" in many use-cases (for business customers) doesn't mean they go bankrupt. They will just lose money and maybe shrink a bit. Also thy are in many other areas then just CPU's including FPGA and hard drives.
  - cbsks 6y ago
    > Intel has no product in the phone/tablet space To be pedantic, Intel does have phone and tablet processors. This doesn't invalidate your point however. I can't easily find a breakdown of mobile cpu market share but I am guessing Intel isn't doing very well. https://www.intel.in/content/www/in/en/products/devices-systems/smartphones.html https://www.intel.in/content/www/in/en/products/devices-syst... https://www.intel.com/content/www/us/en/products/devices-systems/tablets.html https://www.intel.com/content/www/us/en/products/devices-sys...
    - toast0 6y ago
      They canceled the atom for phones product. Right around the time that Microsoft announced the Continuum feature of Windows Phone 10 that gave a desktop(ish) experience when docked, and would have been perfect with an x86 phone. :(
- happytoexplain 6y ago
  The amoral mechanisms of business do not obviate criticisms that are independent of their bottom line, and this simple fact will not be unmade by any amount of the constant and fallacious insistence that people who make such criticisms "don't understand business".
- dathinab 6y ago
  > Because they have them by the balls. Not really, like you mentioned in some ML/HPC contexts GPU computing with commonly Nvidia GPU is a better solution in the desktop marked AMD's recent CPU's are viable alternatives and that also applies for many usages in the server marked. And on mobile, well Intel CPUs never did really compete. Same for game consoles. Oh and for low power embedded systems it's often ARM and for thinks which also need GPU (self driving cars) it's ARM+Nvidea. I mean sure parts of server the server marked are build on things like Intels (not so) secure enclave and then for some gaming workloads Intel CPU's still beat AMD and for not supper expensive software dev. workstations Intel also still is the best choice as the current CPU+embedded GPU chips from AMD for desktop still use their old CPU. Through on thing which shouldn't be forgotten is that they have their hands in a lot of other things including: - FPGA, if you use certain ML algorithm a lot putting them onto a FPGA can be a massive power and time saver. So the Intel CPU + FPGA are quite interesting for such cases. - Graphics, Intel is about to bring out a dedicated graphic card. Probably not interesting for high end usages but it might be a use-full solution for budged setups or GPU servers (It's often monetary better to have multiple smaller cards then one big cards, it's not uncommon for GPU server to have Nvidea 2080ties instead of Quadros etc.). - Hard drives, Optan "SSD" are not very well marked but while they are not necessary the fastest SSD's they have good latencies which can make them preferable for some use-cases. - ... Another thing which can be beneficial for them in the coming 10 years is that they do not depend on TSCM. One funny thing I noticed is that Intel can build a good part of a computer today: CPU + GPU + Motherboard + Network Card + Drives + FPGA + OS (Clear Linux), so add RAM, PSU, Cooling, Cables & Case and you have a Intel only desktop ;-)
  - cma 6y ago
    Intel also own 20% or so of the optics company TSMC relies on for deep UV lithography.
Thaxll 6y ago
Also AVX-512 heat up quite a bit the CPU.
- corysama 6y ago
  For >= 256 bit operations you need to decide to commit to them or not. If you go all-in on them and use them well, you will get the same work in less time and less joules than without them. If they won't help, don't use them. But, popping in and using them for tiny bits would be the slow and hot worst of both worlds.
  - foota 6y ago
    Doesn't this hurt other users/applications on adjacent hyperthreads or cores? Or is it just HT?
  - chrchang523 6y ago
    Nit: most 256-bit AVX2 integer instructions (exception: multiply) do not trigger downclocking.
    - quotemstr 6y ago
      Is there a central list of these safe instructions?
      - chrchang523 6y ago
        I currently follow the guidance in this Stack Overflow answer by Travis Downs: https://stackoverflow.com/a/56861355/3245034 https://stackoverflow.com/a/56861355/3245034 . I'm not aware of a more central source of truth.
    - MaxBarraclough 6y ago
      This turned up over here too. [0] Apparently Intel's CPUs are more inclined to downclock than AMD's. [0] https://news.ycombinator.com/item?id=23810654 https://news.ycombinator.com/item?id=23810654
corysama 6y ago
There's not much use for AVX-512 in the kernel. But, from the people who are using it I've heard good things. It's an enormous collection of new instructions. But, a lot of them came from the Larrabee team --which was probably the greatest case of high-perf software engineers having direct influence over the direction of a CPU. Otherwise, the history SSE and AVX has largely been software engineers requesting features and hardware engineers replying "Do not understand. How does that feature improve our SPECfp score? Rejected."
- gameswithgo 6y ago
  On the one hand AVX-512 is incredible, the performance gains from AVX-2 to AVX-512 are often more than the 2x you would hope for. On the other hand, when you can use AVX-512 you can often use a GPU instead, to greater benefit. So linus may be right, overall.
  - smabie 6y ago
    Are you sure l? Gains between 10% and 50% are pretty common, but I've never heard of a 100% or greater improvement.
    - otherjason 6y ago
      Yes, these applications do exist. The speedups mainly come from the more flexible instruction set that AVX-512 provides (so in many cases you can replace several instructions with just one), plus the increased register set (32 architectural SIMD registers versus 16 on previous generations). If your algorithm isn't sensitive to either one of these, then yes, the speedups are often smaller, particularly if the limiting factor in performance is memory bandwidth and/or latency (AVX-512 doesn't help at all there), or if the speedups aren't enough to overcome clock throttling (which IMO is a bit overblown; most people cite the Cloudflare blog article from a few years ago that complained about throttling on Xeon Silver processors, but throttling is much less of an issue on higher-TDP Gold/Platinum CPUs). However, I have seen specific applications that are >100% faster with AVX-512.
    - 6y ago
etaioinshrdlu 6y ago
Does anyone know if the frequency throttling caused by AVX512 can be circumvented with high-performance CPU cooling? It would at a first glance appear the throttling is not caused by temperature spikes but rather just executing the instructions at all. I wonder how much more FP performance one could extract out of an AVX512 CPU with extreme cooling.
- pstrateman 6y ago
  On Intel CPUs AVX512 instructions always block boost clocks, regardless of actual power budget or cooling capacity. Indeed the boost clocks are on a hard timer in general and cannot run continuously.
- anticensor 6y ago
  Not unless you want erroneous results.
- TinkersW 6y ago
  The throttling will surely be reduced when Intel gets its process issues resolved(7nm), which is probably around when they finally ship AVX512 on desktop.
Koshkin 6y ago
Is this an eye-opener for Intel? I think not. So, then, what's the point (other than to vent one's frustration)?
- dathinab 6y ago
  No point. He just made a commend about something he things is annoying in a mailing list and some media makes a big deal out of it because it's Linus Torvalds. That's all there is to it.
detaro 6y ago
duplicate: https://news.ycombinator.com/item?id=23809335 https://news.ycombinator.com/item?id=23809335
okareaman 6y ago
LT: "I hope AVX512 dies a painful death" I see his month break to work on "unprofessional" behavior didn't include a course on non-violent communication (NVC - https://www.cnvc.org/ https://www.cnvc.org/)
- okareaman 6y ago
  Before I get downvoted to oblivion - a lot of good people worked on that feature because it was their job, presumably some women, and I'm sure they brought passion and creativity to the endeavor, even if it was a dumb management decision. I guess HN approves of telling those people that their work should die a painful death.
  - happytoexplain 6y ago
    I utterly agree with you, but I downvoted you for your inclusion of everybody's favorite self-fulfilling prophecy: "I shall be downvoted".
    - okareaman 6y ago
      Good one! I don't know how many downvotes before it goes completely grey so I was hoping to get a final point in before that happened.
  - Dylan16807 6y ago
    Kill your darlings. It sucks when a lot of people work hard on the wrong thing, but hard work is not a reason to keep a feature.
    - okareaman 6y ago
      I didn't say keep it. I suggested using words less harsh than I hope it dies a painful death. If someone said that about something I worked hard on it would cause me pain
paulmd 6y ago
His idea that AVX-512 is something that's exclusively for floating-point is completely off-base, AVX has included integer operations since AVX2. Widely used in JIT, database, etc. Furthermore, AVX-512 is about much more than doubling the vector width, it is a significant overhaul to the instruction set and adds many new operations and "fills in gaps" that were missing from previous instruction sets. It in fact would be perfectly valid and good to implement AVX-512 with a 256-bit unit that takes twice as long to run 512-bit width instructions. This completely negates all his points about die space utilization right from the start - AVX-512 support does not imply a significantly larger use of space than previous AVX instructions. This would also fix some of the power-related problems on Skylake-SP - after all if you go from 2 512-bit wide units to 2x256 gangable units or 1x256 running at half-rate, that reduces power correspondingly and you no longer need to drop clocks so strongly to offset this, but you keep the functionality added in AVX-512. Furthermore, it's not like there are massive gains in general IPC that haven't been tapped. AVX-512 has taken 25% of the die area in some instances, if you dropped that to AVX2 (assume 12.5% of die area) then it's not like the processor would be 12.5% faster in general, that would translate to maybe 2-3% faster in general and a 30%+ loss in specialty applications. Once you've mostly explored general-purpose gains and are into diminishing returns territory (which modern processors certainly are), it makes sense to start looking at "specialty units", like AVX, or on GPUs you've got tensor cores and BVH traversal units, and so on. These can provide big speedups in key tasks at the cost of very little "general" performance (since that's already in diminishing returns territory). The biggest thing slowing down AVX-512 adoption has been, yet again, 10nm. Right now it is only available on Skylake-X and Skylake-SP products, and more recently Ice Lake (which came out September of last year, in only the ultrabook segment, supplemented by 14nm in the mobile workstation segment as well as the ultrabook segment). So right now it is available in less than 1% of the desktop "fleet" and probably less than 1/8th of the laptop "fleet". There is very little reason to implement code paths for an instruction set that nobody can execute. Over time, as Ice Lake and Tiger Lake build share of the laptop "fleet", Rocket Lake implements it on desktop, and AMD implements it whenever, it will see more usage, just like prior AVX sets. It really is wider-market than people realize. I have seem many people scoff and say "well you'll never see it used in games or whatever", but for many years now there have been games that simply will not run if you don't have AVX (notably many Ubisoft titles), there is no fallback SSE/scalar codepath. In another 10 years you will probably have AVX-512 mandatory games as well. With all due respect to his long career in software engineering, that doesn't necessarily translate to processor design. This is just one person's opinion and you are under no obligation to accept it as gospel just because it's Torvalds'. See also: his weird ZFS rant. (This seems to be a common thing with software engineers in particular, including many on this site - can't count how many "one weird fix from a software engineer to fix [complex domain problem] in [chemical/materials/aerospace engineering]" I've seen. I of course have no particular expertise in processor design either, but the engineers at Intel presumably do, and they thought it was a good idea.
staycoolboy 6y ago
Intel? Dude, have you seen Arm's JavaScript instructions? Or RISC-V's user-defined instructions? (and Arm announced the same thing at Arm Tech Con last year) Someone is missing the boat: custom ISA is the future.
- htfy96 6y ago
  My favorite: Jazelle DBX (direct Java bytecode execution)
- thrwyoilarticle 6y ago
  >Arm's JavaScript instructions Name two
  - matthewaveryusa 6y ago
    Is your point that there's only one (FJCVTZS) ?
    - thrwyoilarticle 6y ago
      Exactly. It's not comparable to the impact AVX has on x86 architectures.
    - hajile 6y ago
      Somewhat off-topic, but only Apple implements ARMv8.3 or 8.4. Does anyone know how much this contributes to their JIT performance on mobile?
  - staycoolboy 6y ago
    Java, Javascript, potato, potahto. Did you miss the part about custom instructions?
    - thrwyoilarticle 6y ago
      Java extensions don't exist any more either. Custom extensions aren't being made to beat benchmarks.
peter_d_sherman 6y ago
I find it amusing, er, ironic, er, amusing -- that after this article, on the same web page, there's a link/blurb which reads: "Nvidia is worth more than Intel for the first time in history. Nvidia is now worth more than Intel, according to the NASDAQ. The GPU company has finally topped the CPU company's market cap (the total value of its outstanding shares) by $251bn..." Well no surprise there. On the one hand, Intel (especially early Intel employees) should be thanked, profusely, for giving us PC history as we know it today. On the other hand, we should seek to honestly recognize what Intel has become today. A mega-corporation, driven by corporate mentality, which always seeks to maximize profits for their shareholders at the expense of all other virtues. Keep in mind I am not criticizing Intel's employees -- only the marching orders that come from the top down. But, as far as I can tell, Intel, as we know it, will not be around in another 30 years. The future of semiconductors is in the following areas: 1) Simple, non-proprietary instruction sets (RISC-V and others) 2) Transparent (or as transparent as possible) and publicly auditable engineering and manufacturing processes 3) Conscientous companies that place virtue first, and are not driven by maximimizing profits for shareholders So on the one hand, Intel is to be thanked, lauded, praised for its role, especially its early role in the beginning of the PC revolution, but on the other hand, I don't see Intel existing as company more than 30 years from now... Although, at that point in time, Intel's past role will always remain important and relevant -- to future students of early computer history...
- dahinds 6y ago
  Your "future of semiconductors" could have been written 30 years ago, and seems no more likely to be true today than it was then. Do you think Nvidia is less proprietary, more transparent, or more virtuous than Intel?
  - Iwan-Zotow 6y ago
    Well, combination of the lead in x86 architecture (a lot of times close to 100% of market supply) combined together with lead in manufacturing (first in process shrink down to 14nm) was unique and highly unlikely to be repeated. Commoditization of architecture (ARM seems to be in the lead by RISC-V might go up) plus separation between chip design houses and manufacture fabs seems to be more efficient market solution. Where it leaves Intel?
zozbot234 6y ago
Previously: https://news.ycombinator.com/item?id=23809335 https://news.ycombinator.com/item?id=23809335
drummer 6y ago
I just love it when Torvalds flips out.
goalieca 6y ago
> This is not the first time Torvalds has directed his ire at Intel. In 2018, Torvalds referred to Intel's Meltdown and Spectre patches as "COMPLETE AND UTTER GARBAGE," in all caps to emphasize his level of anger. I'm 1000% behind him on this point. Fix that first and fix it well. Then get onto fancier stuff that i'll never ever code against.
- shadowgovt 6y ago
  The thing is, "that I'll never ever code against" is context specific. The set of applications that want to be embarrassingly-serial and not utilize any massively-parallel features is shrinking (even problems traditionally solved via serial code can benefit from a parallel re-architecting, assuming the path from language to CPU architecture supports true parallelism).
  - PaulDavisThe1st 6y ago
    The set of applications that benefit from SIMD (i.e. SSE, AVX, AVX-foo) is very different from the set that benefit from parallelism.
    - solidasparagus 6y ago
      That doesn't make much sense to me. SIMD is a parallelization technique.
      - jlokier 6y ago
        I think they mean that SIMD only provides a very particular, limited kind of parallelism. It's only useful for some kinds of parallel problems. Anything where the execution traces diverge significantly requires more execution cores, to sequence them separately. For example serving multiple web pages in parallel. Anything where the executation traces are identical or near-identical across many repetitions in lockstep, is fine with one execution core and SIMD ALUs. For example dense or block matrix arithmetic. Modern GPUs are a hybrid of both ideas. Shared execution cores and SIMD ALUs because of high repetition of identical logic, but still many execution cores (but fewer than ALUs) so there is some amount of decoupled parallelism as well, running different tasks at the same time.
shadowgovt 6y ago
While I love Linus and I think he's excellent at what he does, he's utterly missing the fact that things like AVX-512 sell chips, and that's what Intel's in the business of doing. And best practice in how one writes software will increasingly look like "write it so it executes well in a massively-parallel context" if the driver for chip sales is massively-parallel problems. We've smacked pretty hard into the wall of how fast we can make CPUs by miniaturizing components, and the low-hanging fruit now is parallelization, predictive execution, and the whole host of ways to do more per clock cycle, not speed up clock cycles. But that flies in the face of the traditional embarassingly-serial pattern of the x86 instruction set and computing environment. Much of what Intel's doing these days is trying to open up opportunities for people to change tools to speed up code without having to boil the ocean by throwing the whole serial-instruction model completely out the window (even though, increasingly, code written to that instruction set is really operating like a language that is emulated by the underlying parallel-and-predictive CPU hardware). I think what Linus calls "regular code" isn't going to move chips and we've wrung all the cheap optimizations out of that critical path (and, depending on the details of what is meant by "regular," such code is increasingly going to ram up against an efficiency ceiling unless it can be moved to a model of "Prepare work to do in parallel, execute in parallel, merge results and present to UI").
- colinmhayes 6y ago
  Pretty sure this is exactly what Linus is complaining about. It's not that he doesn't get it, he's upset that intel is spending resources on what he sees as advertising instead of making the product better.
  - shadowgovt 6y ago
    But more direct access to parallel execution hardware is making the product better. It's not making it better for his use case, which is not surprising because Intel is in the business of selling chips, not optimizing for the Linux kernel use case.
- craftinator 6y ago
  Wow, you've turned the "actually useful" reasoning into "marketing useful" reasoning. I'm speechless.
phkahler 6y ago
I'm still waiting for languages to support 2,3, and 4D vectors as first class data types. These are so common it's silly to have people define them. We end up with different implementations sometimes too. Please Rust, please!
- legulere 6y ago
  C# does since recently and also has support for SIMD: https://docs.microsoft.com/en-us/dotnet/api/system.numerics.vector2?view=netcore-3.1 https://docs.microsoft.com/en-us/dotnet/api/system.numerics....
- zelly 6y ago
  https://openjdk.java.net/jeps/338 https://openjdk.java.net/jeps/338 https://www.khronos.org/sycl/ https://www.khronos.org/sycl/
- ezluckyfree 6y ago
  Julia does, and supports SIMD.
- dhosek 6y ago
  AppleSoft BASIC had multi-dimensional arrays back in 1977. It always bugged me that modern languages didn't support this neatly.
  - shele 6y ago
    FORTRAN had arrays 1956...
- sahil-kang 6y ago
  Here are some examples showing Common Lisp’s built-in support for multidimensional arrays: https://lispcookbook.github.io/cl-cookbook/arrays.html https://lispcookbook.github.io/cl-cookbook/arrays.html
- MayeulC 6y ago
  Well... MATLAB (matrix laboratory), and its GNU counterpart Octave kind of do this. The primary data type is an n-dimensional matrix. Of course, there's a lot to say about the rest of the language (and it's untyped/interpreted, though BLAS handles matrix operations so it's extremely fast for vectored code), but it is very nice to work with vast amounts of data in it, and numpy tries to mimic parts of its syntax. That's something I would really like to see in other languages, but depending on the use-case, you can also mix languages... u=rand(5) % 5-by-5 matrix v=rand(5,5,5,5,5,5) % 6-dimensional matrix, each dimension 5 long v2=v(1,2,3,:,:) % 1-by-1-by-1-by-5-by-5 matrix w=u(:,3) % take every line in the third column, so that's a vertical 5-by-1 vector x=5*w*w' % matrix multiplication of w and its transpose, times a scalar y=rand(5).*x % element-wise multiplication
ajayjain 6y ago
Two years ago, I wrote an LLVM compiler pass that automatically upgrades SSE or AVX-2 code to AVX-512 when those instructions are available. It's helpful for getting performance gains for hand engineered code that you don't want to touch. We saw some good gains on integer workloads (unpacking, useful for databases - something I'd call "regular code"): 1.16x speedup going from SSE to AVX-2, and 1.43x speedup going from SSE to AVX-512. Even better speedups are available for FP workloads, though hand-writing the AVX-512 version can work a lot better since programmers can exploit the full range of new instructions available in AVX. https://www.nextgenvec.org/ https://www.nextgenvec.org/ https://arxiv.org/abs/1902.02816 https://arxiv.org/abs/1902.02816
- PaulHoule 6y ago
  The catch is "hand engineered code that you don't want to touch." I helped put an early deep network application into production that used one particular generation of vector instructions and it was clear everyone was traumatized at the process of implemented it to use those vector instructions and would never do it again. We later bought servers that had instructions that we weren't using, but we were so focused on getting the product out the door (which we did) that we left those performance gains on the table. The consequence of the "new instructions every two years" route is that end users don't really experience the performance benefits engineered into the chips. The vast majority of software development organizations are more concerned about support costs than they are about getting the last bit of performance out. (Also, end users are already tired of 200-megabyte binaries, long start times, and other performance decrements that come from high-complexity libraries that contain a huge number of code paths for different CPUs) Many working assembly programmers who are good at SIMD love the Intel approach, maybe because it keeps them in business. People are doing very cool things in the parsing space (e.g. it is shocking how slow it is to parse ascii-formatted numbers, JSON, XML, RDF, ...) with SIMD instructions. However, the old tradition in vector computing is the variable-sized vector unit like what the ILLIAC had or the old Crays, the vector accelerator for the IBM 3090, etc. ARM has the scalable vector instructions which are organized that way. ARM's Helium had a nice middle ground of having "small, medium and large" implementations available which all run the same code. You might get higher peak peformance on Intel's road, but higher realized performance with ARM.
anarazel 6y ago
x86 instructions I'd like to see are atomic instructions with lower global memory ordering guarantees. TSO is nice, but there's enough performance sensitive concurrent code where opting out would be useful.
tbenst 6y ago
I see a huge bump in numpy performance with AVX-512, to the point where I wouldn’t buy a cpu without it. I don’t know that I understand the critique—-is it because these instructions are Intel specific and not on AMD? Seems obviously useful for scientific computing.
- quotemstr 6y ago
  Numpy is grossly inefficient anyway due to its eager evaluation model and lack of operator fusion.
fierarul 6y ago
Kinda odd to see the title 'founder'. Linux is no startup or company. Linus is more like the original author, maintainer or creator of Linux.
- zenhack 6y ago
  The word "founder" just means "person who started a thing." The use as a synonym for entrepreneur is something I basically haven't seen anywhere outside of very business-focused contexts.
shmerl 6y ago
It's an old argument of having too many special purpose circuits vs leaving more room for the rest. Linus has a point.
posedge 6y ago
"Linux founder" Folks, anyone who knows what Linux is also knows who Linus Torvalds is.
dottrap 6y ago
Seems like many people here haven't actually read Linus's specific thoughts on AVX-512, and are accusing him of rejecting SIMD entirely or the usefulness of FP performance entirely. This is not an accurate representation of his position and he singles out AVX-512 differently from SSE/AVX/AVX2. Here is a link to the thread directly from Linus explaining his position on MMX/SSE, AVX/AVX2, AVX512. His complaints on AVX512 are both about fragmentation and regressing from the learned lessons from their prior generations. And he also looks to NEON and SVE2 and suggesting ARM looks seems much saner to him: "So just as a bystander, I'm looking at AVX512, and I'm looking at SVE2, and I'm going "AVX512 really is nasty, isn't it"?"" https://www.realworldtech.com/forum/?threadid=193189&curpostid=193248 https://www.realworldtech.com/forum/?threadid=193189&curpost...
deleted 6y ago
[deleted]

287 points by rsecora 6y ago

Torvalds clearly does not understand the brutality of business. Intel does not care at all about customers it have at the moment. Because they have them by the balls. After many years of struggle only Apple (with its unlimited resource) was able to switch to ARM. So they don’t care. They only care about long term market, which is HPC and ML workloads. Because Nvidia is destroying anybody in that market. Look at their stock. I’ve got a news for Torvalds, it going to get bad for Intel.

cameldrv 6y ago
If there were ever a time where Intel had its customers by the balls the least in the past twenty years, it's now. AMD is extremely competitive in the server and desktop space, ARM/Apple is becoming competitive in the laptop space, Intel has no product in the phone/tablet space, and they are noncompetitive in the HPC/DL accelerator space. If there's anything that has typified Intel in the past decade it's a generalized failure to execute. There's been very little innovation in the core product since Haswell in 2013.
- DubiousPusher 6y ago
  Yeah for anyone who was a computer enthusiast in the 90s and 00s the rise of ARM has been an astonishing development comparable to the ubiquity of Linux and decline of Windows.
  - Koshkin 6y ago
    > ubiquity of Linux and decline of Windows Should I read this as sarcasm?
    - ardy42 6y ago
      >> ubiquity of Linux and decline of Windows > Should I read this as sarcasm? It could only be sarcastic if he's referring to "Linux on the desktop." I don't have any numbers, but I wouldn't be surprised if he was correct about servers.
      - DubiousPusher 6y ago
        Correct. I am referring to everything except desktop computing. I can see how this would be confusing as I was just referencing desktop prossesor market patterns of the 90s/00s. But I do think Windows's position in the desktop space is somewhat unsustainable at this point. I personally prefer Windows but I just don't see how a heterogenous user interface experience (with users on iOS and Android for mobile and Windows for desktop) will abide for long. I think it's only a matter of time before mobile OSes make some serious inroads to desktop. Though I suppose Google has been salivating at that thought for neaely a decade.
      - cameldrv 6y ago
        If you look at the overall "computing devices with a reasonably high performance CPU" market, Linux has won the server market, and through Android, won the phone/tablet market. If you squint a bit, you can lump MacOS and iOS in this in that they have a Unix core and use a lot of the same software stack as Linux. 50 years ago, IBM owned the computing market with mainframes. They still dominate the mainframe market, that's just become a smaller and smaller portion of the overall computing market as time has gone on.
    - macintux 6y ago
      In both the server and especially mobile space Windows has lost its mojo and Linux has been a beneficiary.
    - RodgerTheGreat 6y ago
      Linux is ubiquitous. It runs on embedded devices, cell phones, and tablets which surround us. Linux runs most of the computers which underpin websites and services we interact with daily, and it is the only serious choice for HPC. A few people even run it on their laptops. Windows has declined. It is still used extensively, but Microsoft no longer dictates the browser market. Microsoft Office is commonplace, but has genuine marketshare competition in alternatives like Google Docs. Developers increasingly build "desktop" applications as web-based or multiplatform-first instead of Windows-exclusive, with the notable exception of AAA games. The Linux subsystem for Windows is a direct admission by Microsoft that developers want to work with Linux-based software for many tasks.
- trekrich 6y ago
  Then its only a matter of time before they go bankrupt.
  - rorykoehler 6y ago
    They have the cash to get out of this if they make the right moves.
    - mindcrime 6y ago
      Exactly. A single well-time and well-executed acquisition could change the whole game. Of course we all know that executing acquisitions well is easier said than done, and I don't have a specific target in mind when I say this. It's more of an "in principle" speculation than a concrete suggestion at the moment.
      - rorykoehler 6y ago
        Softbank are looking to sell some or all of their ARM holdings.
  - dathinab 6y ago
    Very unlikely. Just because they are no longer "without alternatives" in many use-cases (for business customers) doesn't mean they go bankrupt. They will just lose money and maybe shrink a bit. Also thy are in many other areas then just CPU's including FPGA and hard drives.
- cbsks 6y ago
  > Intel has no product in the phone/tablet space To be pedantic, Intel does have phone and tablet processors. This doesn't invalidate your point however. I can't easily find a breakdown of mobile cpu market share but I am guessing Intel isn't doing very well. https://www.intel.in/content/www/in/en/products/devices-systems/smartphones.html https://www.intel.in/content/www/in/en/products/devices-syst... https://www.intel.com/content/www/us/en/products/devices-systems/tablets.html https://www.intel.com/content/www/us/en/products/devices-sys...
  - toast0 6y ago
    They canceled the atom for phones product. Right around the time that Microsoft announced the Continuum feature of Windows Phone 10 that gave a desktop(ish) experience when docked, and would have been perfect with an x86 phone. :(
happytoexplain 6y ago
The amoral mechanisms of business do not obviate criticisms that are independent of their bottom line, and this simple fact will not be unmade by any amount of the constant and fallacious insistence that people who make such criticisms "don't understand business".
dathinab 6y ago
> Because they have them by the balls. Not really, like you mentioned in some ML/HPC contexts GPU computing with commonly Nvidia GPU is a better solution in the desktop marked AMD's recent CPU's are viable alternatives and that also applies for many usages in the server marked. And on mobile, well Intel CPUs never did really compete. Same for game consoles. Oh and for low power embedded systems it's often ARM and for thinks which also need GPU (self driving cars) it's ARM+Nvidea. I mean sure parts of server the server marked are build on things like Intels (not so) secure enclave and then for some gaming workloads Intel CPU's still beat AMD and for not supper expensive software dev. workstations Intel also still is the best choice as the current CPU+embedded GPU chips from AMD for desktop still use their old CPU. Through on thing which shouldn't be forgotten is that they have their hands in a lot of other things including: - FPGA, if you use certain ML algorithm a lot putting them onto a FPGA can be a massive power and time saver. So the Intel CPU + FPGA are quite interesting for such cases. - Graphics, Intel is about to bring out a dedicated graphic card. Probably not interesting for high end usages but it might be a use-full solution for budged setups or GPU servers (It's often monetary better to have multiple smaller cards then one big cards, it's not uncommon for GPU server to have Nvidea 2080ties instead of Quadros etc.). - Hard drives, Optan "SSD" are not very well marked but while they are not necessary the fastest SSD's they have good latencies which can make them preferable for some use-cases. - ... Another thing which can be beneficial for them in the coming 10 years is that they do not depend on TSCM. One funny thing I noticed is that Intel can build a good part of a computer today: CPU + GPU + Motherboard + Network Card + Drives + FPGA + OS (Clear Linux), so add RAM, PSU, Cooling, Cables & Case and you have a Intel only desktop ;-)
- cma 6y ago
  Intel also own 20% or so of the optics company TSMC relies on for deep UV lithography.

Thaxll 6y ago

Also AVX-512 heat up quite a bit the CPU.

corysama 6y ago
For >= 256 bit operations you need to decide to commit to them or not. If you go all-in on them and use them well, you will get the same work in less time and less joules than without them. If they won't help, don't use them. But, popping in and using them for tiny bits would be the slow and hot worst of both worlds.
- foota 6y ago
  Doesn't this hurt other users/applications on adjacent hyperthreads or cores? Or is it just HT?
- chrchang523 6y ago
  Nit: most 256-bit AVX2 integer instructions (exception: multiply) do not trigger downclocking.
  - quotemstr 6y ago
    Is there a central list of these safe instructions?
    - chrchang523 6y ago
      I currently follow the guidance in this Stack Overflow answer by Travis Downs: https://stackoverflow.com/a/56861355/3245034 https://stackoverflow.com/a/56861355/3245034 . I'm not aware of a more central source of truth.
  - MaxBarraclough 6y ago
    This turned up over here too. [0] Apparently Intel's CPUs are more inclined to downclock than AMD's. [0] https://news.ycombinator.com/item?id=23810654 https://news.ycombinator.com/item?id=23810654

corysama 6y ago

There's not much use for AVX-512 in the kernel. But, from the people who are using it I've heard good things. It's an enormous collection of new instructions. But, a lot of them came from the Larrabee team --which was probably the greatest case of high-perf software engineers having direct influence over the direction of a CPU. Otherwise, the history SSE and AVX has largely been software engineers requesting features and hardware engineers replying "Do not understand. How does that feature improve our SPECfp score? Rejected."

gameswithgo 6y ago
On the one hand AVX-512 is incredible, the performance gains from AVX-2 to AVX-512 are often more than the 2x you would hope for. On the other hand, when you can use AVX-512 you can often use a GPU instead, to greater benefit. So linus may be right, overall.
- smabie 6y ago
  Are you sure l? Gains between 10% and 50% are pretty common, but I've never heard of a 100% or greater improvement.
  - otherjason 6y ago
    Yes, these applications do exist. The speedups mainly come from the more flexible instruction set that AVX-512 provides (so in many cases you can replace several instructions with just one), plus the increased register set (32 architectural SIMD registers versus 16 on previous generations). If your algorithm isn't sensitive to either one of these, then yes, the speedups are often smaller, particularly if the limiting factor in performance is memory bandwidth and/or latency (AVX-512 doesn't help at all there), or if the speedups aren't enough to overcome clock throttling (which IMO is a bit overblown; most people cite the Cloudflare blog article from a few years ago that complained about throttling on Xeon Silver processors, but throttling is much less of an issue on higher-TDP Gold/Platinum CPUs). However, I have seen specific applications that are >100% faster with AVX-512.
  - 6y ago

etaioinshrdlu 6y ago

Does anyone know if the frequency throttling caused by AVX512 can be circumvented with high-performance CPU cooling? It would at a first glance appear the throttling is not caused by temperature spikes but rather just executing the instructions at all. I wonder how much more FP performance one could extract out of an AVX512 CPU with extreme cooling.

pstrateman 6y ago
On Intel CPUs AVX512 instructions always block boost clocks, regardless of actual power budget or cooling capacity. Indeed the boost clocks are on a hard timer in general and cannot run continuously.
anticensor 6y ago
Not unless you want erroneous results.
TinkersW 6y ago
The throttling will surely be reduced when Intel gets its process issues resolved(7nm), which is probably around when they finally ship AVX512 on desktop.

Koshkin 6y ago

Is this an eye-opener for Intel? I think not. So, then, what's the point (other than to vent one's frustration)?

dathinab 6y ago
No point. He just made a commend about something he things is annoying in a mailing list and some media makes a big deal out of it because it's Linus Torvalds. That's all there is to it.

detaro 6y ago

duplicate: https://news.ycombinator.com/item?id=23809335 https://news.ycombinator.com/item?id=23809335

okareaman 6y ago

LT: "I hope AVX512 dies a painful death" I see his month break to work on "unprofessional" behavior didn't include a course on non-violent communication (NVC - https://www.cnvc.org/ https://www.cnvc.org/)

okareaman 6y ago
Before I get downvoted to oblivion - a lot of good people worked on that feature because it was their job, presumably some women, and I'm sure they brought passion and creativity to the endeavor, even if it was a dumb management decision. I guess HN approves of telling those people that their work should die a painful death.
- happytoexplain 6y ago
  I utterly agree with you, but I downvoted you for your inclusion of everybody's favorite self-fulfilling prophecy: "I shall be downvoted".
  - okareaman 6y ago
    Good one! I don't know how many downvotes before it goes completely grey so I was hoping to get a final point in before that happened.
- Dylan16807 6y ago
  Kill your darlings. It sucks when a lot of people work hard on the wrong thing, but hard work is not a reason to keep a feature.
  - okareaman 6y ago
    I didn't say keep it. I suggested using words less harsh than I hope it dies a painful death. If someone said that about something I worked hard on it would cause me pain

paulmd 6y ago

His idea that AVX-512 is something that's exclusively for floating-point is completely off-base, AVX has included integer operations since AVX2. Widely used in JIT, database, etc. Furthermore, AVX-512 is about much more than doubling the vector width, it is a significant overhaul to the instruction set and adds many new operations and "fills in gaps" that were missing from previous instruction sets. It in fact would be perfectly valid and good to implement AVX-512 with a 256-bit unit that takes twice as long to run 512-bit width instructions. This completely negates all his points about die space utilization right from the start - AVX-512 support does not imply a significantly larger use of space than previous AVX instructions. This would also fix some of the power-related problems on Skylake-SP - after all if you go from 2 512-bit wide units to 2x256 gangable units or 1x256 running at half-rate, that reduces power correspondingly and you no longer need to drop clocks so strongly to offset this, but you keep the functionality added in AVX-512. Furthermore, it's not like there are massive gains in general IPC that haven't been tapped. AVX-512 has taken 25% of the die area in some instances, if you dropped that to AVX2 (assume 12.5% of die area) then it's not like the processor would be 12.5% faster in general, that would translate to maybe 2-3% faster in general and a 30%+ loss in specialty applications. Once you've mostly explored general-purpose gains and are into diminishing returns territory (which modern processors certainly are), it makes sense to start looking at "specialty units", like AVX, or on GPUs you've got tensor cores and BVH traversal units, and so on. These can provide big speedups in key tasks at the cost of very little "general" performance (since that's already in diminishing returns territory). The biggest thing slowing down AVX-512 adoption has been, yet again, 10nm. Right now it is only available on Skylake-X and Skylake-SP products, and more recently Ice Lake (which came out September of last year, in only the ultrabook segment, supplemented by 14nm in the mobile workstation segment as well as the ultrabook segment). So right now it is available in less than 1% of the desktop "fleet" and probably less than 1/8th of the laptop "fleet". There is very little reason to implement code paths for an instruction set that nobody can execute. Over time, as Ice Lake and Tiger Lake build share of the laptop "fleet", Rocket Lake implements it on desktop, and AMD implements it whenever, it will see more usage, just like prior AVX sets. It really is wider-market than people realize. I have seem many people scoff and say "well you'll never see it used in games or whatever", but for many years now there have been games that simply will not run if you don't have AVX (notably many Ubisoft titles), there is no fallback SSE/scalar codepath. In another 10 years you will probably have AVX-512 mandatory games as well. With all due respect to his long career in software engineering, that doesn't necessarily translate to processor design. This is just one person's opinion and you are under no obligation to accept it as gospel just because it's Torvalds'. See also: his weird ZFS rant. (This seems to be a common thing with software engineers in particular, including many on this site - can't count how many "one weird fix from a software engineer to fix [complex domain problem] in [chemical/materials/aerospace engineering]" I've seen. I of course have no particular expertise in processor design either, but the engineers at Intel presumably do, and they thought it was a good idea.

staycoolboy 6y ago

Intel? Dude, have you seen Arm's JavaScript instructions? Or RISC-V's user-defined instructions? (and Arm announced the same thing at Arm Tech Con last year) Someone is missing the boat: custom ISA is the future.

htfy96 6y ago
My favorite: Jazelle DBX (direct Java bytecode execution)
thrwyoilarticle 6y ago
>Arm's JavaScript instructions Name two
- matthewaveryusa 6y ago
  Is your point that there's only one (FJCVTZS) ?
  - thrwyoilarticle 6y ago
    Exactly. It's not comparable to the impact AVX has on x86 architectures.
  - hajile 6y ago
    Somewhat off-topic, but only Apple implements ARMv8.3 or 8.4. Does anyone know how much this contributes to their JIT performance on mobile?
- staycoolboy 6y ago
  Java, Javascript, potato, potahto. Did you miss the part about custom instructions?
  - thrwyoilarticle 6y ago
    Java extensions don't exist any more either. Custom extensions aren't being made to beat benchmarks.

peter_d_sherman 6y ago

I find it amusing, er, ironic, er, amusing -- that after this article, on the same web page, there's a link/blurb which reads: "Nvidia is worth more than Intel for the first time in history. Nvidia is now worth more than Intel, according to the NASDAQ. The GPU company has finally topped the CPU company's market cap (the total value of its outstanding shares) by $251bn..." Well no surprise there. On the one hand, Intel (especially early Intel employees) should be thanked, profusely, for giving us PC history as we know it today. On the other hand, we should seek to honestly recognize what Intel has become today. A mega-corporation, driven by corporate mentality, which always seeks to maximize profits for their shareholders at the expense of all other virtues. Keep in mind I am not criticizing Intel's employees -- only the marching orders that come from the top down. But, as far as I can tell, Intel, as we know it, will not be around in another 30 years. The future of semiconductors is in the following areas: 1) Simple, non-proprietary instruction sets (RISC-V and others) 2) Transparent (or as transparent as possible) and publicly auditable engineering and manufacturing processes 3) Conscientous companies that place virtue first, and are not driven by maximimizing profits for shareholders So on the one hand, Intel is to be thanked, lauded, praised for its role, especially its early role in the beginning of the PC revolution, but on the other hand, I don't see Intel existing as company more than 30 years from now... Although, at that point in time, Intel's past role will always remain important and relevant -- to future students of early computer history...

dahinds 6y ago
Your "future of semiconductors" could have been written 30 years ago, and seems no more likely to be true today than it was then. Do you think Nvidia is less proprietary, more transparent, or more virtuous than Intel?
- Iwan-Zotow 6y ago
  Well, combination of the lead in x86 architecture (a lot of times close to 100% of market supply) combined together with lead in manufacturing (first in process shrink down to 14nm) was unique and highly unlikely to be repeated. Commoditization of architecture (ARM seems to be in the lead by RISC-V might go up) plus separation between chip design houses and manufacture fabs seems to be more efficient market solution. Where it leaves Intel?

zozbot234 6y ago

Previously: https://news.ycombinator.com/item?id=23809335 https://news.ycombinator.com/item?id=23809335

drummer 6y ago

I just love it when Torvalds flips out.

goalieca 6y ago

> This is not the first time Torvalds has directed his ire at Intel. In 2018, Torvalds referred to Intel's Meltdown and Spectre patches as "COMPLETE AND UTTER GARBAGE," in all caps to emphasize his level of anger. I'm 1000% behind him on this point. Fix that first and fix it well. Then get onto fancier stuff that i'll never ever code against.

shadowgovt 6y ago
The thing is, "that I'll never ever code against" is context specific. The set of applications that want to be embarrassingly-serial and not utilize any massively-parallel features is shrinking (even problems traditionally solved via serial code can benefit from a parallel re-architecting, assuming the path from language to CPU architecture supports true parallelism).
- PaulDavisThe1st 6y ago
  The set of applications that benefit from SIMD (i.e. SSE, AVX, AVX-foo) is very different from the set that benefit from parallelism.
  - solidasparagus 6y ago
    That doesn't make much sense to me. SIMD is a parallelization technique.
    - jlokier 6y ago
      I think they mean that SIMD only provides a very particular, limited kind of parallelism. It's only useful for some kinds of parallel problems. Anything where the execution traces diverge significantly requires more execution cores, to sequence them separately. For example serving multiple web pages in parallel. Anything where the executation traces are identical or near-identical across many repetitions in lockstep, is fine with one execution core and SIMD ALUs. For example dense or block matrix arithmetic. Modern GPUs are a hybrid of both ideas. Shared execution cores and SIMD ALUs because of high repetition of identical logic, but still many execution cores (but fewer than ALUs) so there is some amount of decoupled parallelism as well, running different tasks at the same time.

shadowgovt 6y ago

While I love Linus and I think he's excellent at what he does, he's utterly missing the fact that things like AVX-512 sell chips, and that's what Intel's in the business of doing. And best practice in how one writes software will increasingly look like "write it so it executes well in a massively-parallel context" if the driver for chip sales is massively-parallel problems. We've smacked pretty hard into the wall of how fast we can make CPUs by miniaturizing components, and the low-hanging fruit now is parallelization, predictive execution, and the whole host of ways to do more per clock cycle, not speed up clock cycles. But that flies in the face of the traditional embarassingly-serial pattern of the x86 instruction set and computing environment. Much of what Intel's doing these days is trying to open up opportunities for people to change tools to speed up code without having to boil the ocean by throwing the whole serial-instruction model completely out the window (even though, increasingly, code written to that instruction set is really operating like a language that is emulated by the underlying parallel-and-predictive CPU hardware). I think what Linus calls "regular code" isn't going to move chips and we've wrung all the cheap optimizations out of that critical path (and, depending on the details of what is meant by "regular," such code is increasingly going to ram up against an efficiency ceiling unless it can be moved to a model of "Prepare work to do in parallel, execute in parallel, merge results and present to UI").

colinmhayes 6y ago
Pretty sure this is exactly what Linus is complaining about. It's not that he doesn't get it, he's upset that intel is spending resources on what he sees as advertising instead of making the product better.
- shadowgovt 6y ago
  But more direct access to parallel execution hardware is making the product better. It's not making it better for his use case, which is not surprising because Intel is in the business of selling chips, not optimizing for the Linux kernel use case.
craftinator 6y ago
Wow, you've turned the "actually useful" reasoning into "marketing useful" reasoning. I'm speechless.

phkahler 6y ago

I'm still waiting for languages to support 2,3, and 4D vectors as first class data types. These are so common it's silly to have people define them. We end up with different implementations sometimes too. Please Rust, please!

legulere 6y ago
C# does since recently and also has support for SIMD: https://docs.microsoft.com/en-us/dotnet/api/system.numerics.vector2?view=netcore-3.1 https://docs.microsoft.com/en-us/dotnet/api/system.numerics....
zelly 6y ago
https://openjdk.java.net/jeps/338 https://openjdk.java.net/jeps/338 https://www.khronos.org/sycl/ https://www.khronos.org/sycl/
ezluckyfree 6y ago
Julia does, and supports SIMD.
dhosek 6y ago
AppleSoft BASIC had multi-dimensional arrays back in 1977. It always bugged me that modern languages didn't support this neatly.
- shele 6y ago
  FORTRAN had arrays 1956...
sahil-kang 6y ago
Here are some examples showing Common Lisp’s built-in support for multidimensional arrays: https://lispcookbook.github.io/cl-cookbook/arrays.html https://lispcookbook.github.io/cl-cookbook/arrays.html
MayeulC 6y ago
Well... MATLAB (matrix laboratory), and its GNU counterpart Octave kind of do this. The primary data type is an n-dimensional matrix. Of course, there's a lot to say about the rest of the language (and it's untyped/interpreted, though BLAS handles matrix operations so it's extremely fast for vectored code), but it is very nice to work with vast amounts of data in it, and numpy tries to mimic parts of its syntax. That's something I would really like to see in other languages, but depending on the use-case, you can also mix languages... u=rand(5) % 5-by-5 matrix v=rand(5,5,5,5,5,5) % 6-dimensional matrix, each dimension 5 long v2=v(1,2,3,:,:) % 1-by-1-by-1-by-5-by-5 matrix w=u(:,3) % take every line in the third column, so that's a vertical 5-by-1 vector x=5*w*w' % matrix multiplication of w and its transpose, times a scalar y=rand(5).*x % element-wise multiplication

ajayjain 6y ago

Two years ago, I wrote an LLVM compiler pass that automatically upgrades SSE or AVX-2 code to AVX-512 when those instructions are available. It's helpful for getting performance gains for hand engineered code that you don't want to touch. We saw some good gains on integer workloads (unpacking, useful for databases - something I'd call "regular code"): 1.16x speedup going from SSE to AVX-2, and 1.43x speedup going from SSE to AVX-512. Even better speedups are available for FP workloads, though hand-writing the AVX-512 version can work a lot better since programmers can exploit the full range of new instructions available in AVX. https://www.nextgenvec.org/ https://www.nextgenvec.org/ https://arxiv.org/abs/1902.02816 https://arxiv.org/abs/1902.02816

PaulHoule 6y ago
The catch is "hand engineered code that you don't want to touch." I helped put an early deep network application into production that used one particular generation of vector instructions and it was clear everyone was traumatized at the process of implemented it to use those vector instructions and would never do it again. We later bought servers that had instructions that we weren't using, but we were so focused on getting the product out the door (which we did) that we left those performance gains on the table. The consequence of the "new instructions every two years" route is that end users don't really experience the performance benefits engineered into the chips. The vast majority of software development organizations are more concerned about support costs than they are about getting the last bit of performance out. (Also, end users are already tired of 200-megabyte binaries, long start times, and other performance decrements that come from high-complexity libraries that contain a huge number of code paths for different CPUs) Many working assembly programmers who are good at SIMD love the Intel approach, maybe because it keeps them in business. People are doing very cool things in the parsing space (e.g. it is shocking how slow it is to parse ascii-formatted numbers, JSON, XML, RDF, ...) with SIMD instructions. However, the old tradition in vector computing is the variable-sized vector unit like what the ILLIAC had or the old Crays, the vector accelerator for the IBM 3090, etc. ARM has the scalable vector instructions which are organized that way. ARM's Helium had a nice middle ground of having "small, medium and large" implementations available which all run the same code. You might get higher peak peformance on Intel's road, but higher realized performance with ARM.

anarazel 6y ago

x86 instructions I'd like to see are atomic instructions with lower global memory ordering guarantees. TSO is nice, but there's enough performance sensitive concurrent code where opting out would be useful.

tbenst 6y ago

I see a huge bump in numpy performance with AVX-512, to the point where I wouldn’t buy a cpu without it. I don’t know that I understand the critique—-is it because these instructions are Intel specific and not on AMD? Seems obviously useful for scientific computing.

quotemstr 6y ago
Numpy is grossly inefficient anyway due to its eager evaluation model and lack of operator fusion.

fierarul 6y ago

Kinda odd to see the title 'founder'. Linux is no startup or company. Linus is more like the original author, maintainer or creator of Linux.

zenhack 6y ago
The word "founder" just means "person who started a thing." The use as a synonym for entrepreneur is something I basically haven't seen anywhere outside of very business-focused contexts.

shmerl 6y ago

It's an old argument of having too many special purpose circuits vs leaving more room for the rest. Linus has a point.

posedge 6y ago

"Linux founder" Folks, anyone who knows what Linux is also knows who Linus Torvalds is.

dottrap 6y ago

Seems like many people here haven't actually read Linus's specific thoughts on AVX-512, and are accusing him of rejecting SIMD entirely or the usefulness of FP performance entirely. This is not an accurate representation of his position and he singles out AVX-512 differently from SSE/AVX/AVX2. Here is a link to the thread directly from Linus explaining his position on MMX/SSE, AVX/AVX2, AVX512. His complaints on AVX512 are both about fragmentation and regressing from the learned lessons from their prior generations. And he also looks to NEON and SVE2 and suggesting ARM looks seems much saner to him: "So just as a bystander, I'm looking at AVX512, and I'm looking at SVE2, and I'm going "AVX512 really is nasty, isn't it"?"" https://www.realworldtech.com/forum/?threadid=193189&curpostid=193248 https://www.realworldtech.com/forum/?threadid=193189&curpost...

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