5 ms·

> elegance matters absolutely, but no need for strong violence. ANSI C and RISC-V are doing fine. > x86-64 which is not dying true. technically speaking, it

by kelas 3y ago

> elegance matters absolutely, but no need for strong violence. ANSI C and RISC-V are doing fine. > x86-64 which is not dying true. technically speaking, it is long gone - any Intel CPU since about Pentium Pro is actually a well-hidden RISC, because it is more efficient. Sure that requires a pretty beefy CISC decoder in front, but the sheer power of having a virtual 8086 mode next to amd64 must totally justify all that extra TDP. > [x86 is] something students can run on real hardware, and that's cool and engaging also true, but nothing compares to booting the real xv6 on a real RISC-V system for the first time, which is easy and fun (and cheap, if we’re talking value). i recommend.

nine_k 3y ago
I'd say that C is not elegant as a language at all. It's a good (as in "working") solution of many problems that other system languages had in late 1960s, and I'd hazard to say that the highly economical ways that were used to solve them are elegant. E.g. using #include is terrible from many angles, but is elegant as a highly minimalist way to solve the modularity problem (reduce the problem to one already solved).
- kelas 3y ago
  > C is not elegant okay, tastes differ, but it remains what it was in one of its original definitions: a sufficiently portable assembly. > #include hell / modularity okay, so rust has cargo, so we’re all better now, right? but what if someone will dare to argue that C has a whole bunch of cargos, some less terrible than others, if we reframe the problem like so: $ [rpm|dpkg|dnf|yum|apt|brew|pkg-add] install libcurl libcurl-dev(el) (this makes me wonder how any software even works anymore in absence of universal cargo cult, but hey)
  - viraptor 3y ago
    Different things entirely. System-specific packages have no concept of C building or linking. Things work because of some agreement about paths + pkgconfig + others. This is very far from the idea of a dependency manager like cargo which is very much aware of project-specific and language features.
    - kelas 3y ago
      > Different things entirely yes, they are. > System-specific packages have no concept of C building or linking. every day i learn something new, but this time around I’m gonna go ahead a tell you that you are very mistaken. > Things work because of some agreement about paths + pkgconfig + others. True. By convention, we call it “convention”, or “standard” for short, e.g. POSIX or ISO C. Call us back once you have something like that in rustland. > This is very far from the idea of a dependency manager like cargo which is very much aware of project-specific and language features. All good and sound, and makes total sense for userland software. But what is being discussed here is an operating system and core userland. If you can imagine that to be your “project”, such as linux or OpenBSD, maybe my tongue-in-cheek comparison of a system-wide dependency manager suddenly looks less dissimilar to cargo. needless to say, things like Linux and OpenBSD will stay written in C for a little while longer. In case of BSD specifically, you can go as crazy as to bump and rebuild your entire system from source in place, kernel and userland. BSD is one pretty old cargo cult in that sense, and pretty cool, i might add. > language features right… rust 2018 edition is not really rust as of 2023, or is it? This where those pesky standards come very handy.
      - viraptor 3y ago
        > tell you that you are very mistaken. Go on then. Beyond RPMs ability to depend on soname, what else is there on the structure/installation/usage side (not on the building side which can include whatever scripts you want). Where are they now aware of the libraries more than tar.gz is?
        kelas 3y ago
        I think I see your point. Thing is, a C program can be built and executed without that cargo dependency pyramid sandwiched into a gigantic runtime polyp. The whole operating system is your environment, and yes - if ‘man ldconfig’ is not your friend, then maybe pkg-config is, or, worse to worst, link against project-local structure, where you can indeed build the bejesus out of your imagination and ship it. That’s ok. It’s linux, after all. That’s what we do for embedded systems, anyway. I haven’t seen much success for rust in this department, although people are clearly trying to make it work. It just keeps coming out fat and ugly. A few more decades of hard push, call me a maybe. Do you know what riscv version of xv6 rev3 compiles to in terms of object size? I will not spoil it for you, but it compiles to total shreds.
  - lproven 3y ago
    > a sufficiently portable assembly. No, it isn't, and it hasn't been for about 40 years. « C Is Not a Low-level Language Your computer is not a fast PDP-11. » https://queue.acm.org/detail.cfm?id=3212479 https://queue.acm.org/detail.cfm?id=3212479 David Chisnall, ACM Queue, April 30, 2018
    - kelas 3y ago
      Sounds expensive, thanks. So: Preface to the Digital Edition of Kernighan and Ritchie's The C Programming Language Oct 31, 2012 “… Remarkably, in spite of all of this change, C retains a central position. It is still the core language for operating system implementation and tool building. It remains unequaled for portability, efficiency, and ability to get close to the hardware when necessary. C has sometimes been called a high-level assembler, and this is not a bad characterization of how well it spans the range from intricate data structure and control flow to the lowest level of external devices.” (sorry, I messed up the lyrics a bit, but also I didn’t, really) Also, my computer is a fast Turing machine. And so is yours.
      - lproven 3y ago
        I can't make any sense of a single sentence of that. > Sounds expensive, thanks Huh? What does? The paper is entirely free. That's why I posted a link. Go read it. It's not very long, it's interesting, it's accessible, it's provocative and insightful and profound. > Kernighan and Ritchie Creator of C is biased about the language he created. Shock. Pictures at 11. K&R was published in 1988. Then, your PC was to some degree a fast PDP-11. That was over 1/3 of a century ago and it is no longer even remotely true. > Also, my computer is a fast Turing machine. And so is yours. Reductio ad absurdam. Here's a talk from the inventor of the Arm architecture. It's pretty good. https://www.youtube.com/watch?v=6lOnpQgn-9s https://www.youtube.com/watch?v=6lOnpQgn-9s She talks about her more recent baby, Firepath. It can, for instance, in a single opcode and a single CPU cycle load 4 separate different 32 bit integers, multiply them by 4 other 32-bit ints and store the result. (Around 25 min in but it's very worth watching the whole talk.) Her point is that C can't express stuff like this well at all. A modern CPU has dozens of execution units doing stuff in parallel, applying matrix operations and transformations to multiple different streams of data simultaneously: SIMD and MIMD combined. C has no way of even beginning to express any of this. C is no more a high-level assembly language for any 21st century CPU than a Falcon-9 reusable orbital launch vehicle is a space-going version of the Wright Flyer.
phendrenad2 3y ago
> nothing compares to booting the real xv6 on a real RISC-V system for the first time Why is that? > any Intel CPU since about Pentium Pro is actually a well-hidden RISC Well if it's well-hidden, it doesn't matter to the person learning to write an OS. ;)
- kelas 3y ago
  > Why is that? you said it best - the “tinkering” part is a small thing that makes all the difference when one is first led up to a computer. > if it's hidden, it doesn't matter right… and if you ignore it, maybe it’ll go away. like Intel Management Engine, perhaps. Which OS does it run, if you know? :)
  - phendrenad2 3y ago
    > the “tinkering” part is a small thing that makes all the difference when one is first led up to a computer True, but when making an OS, assembly code is an incredibly small part of it. You basically need to run a few instructions to put the processor in the right mode, and you need ONE line of assembly code (often inline C) to allow usermode to call supervisor mode. When choosing an architecture for a learning OS, I think other factors would dominate, like availability of hardware (many people have a PC already, saving them $100-$200 on RISC-V hardware). > right… and if you ignore it, maybe it’ll go away. like Intel Management Engine, perhaps. Which OS does it run, if you know? :) I'm not interested in gatekeeping tech to only those who care about personal privacy, so I consider this line of thought completely irrelevant to the discussion. But that's just me...
    - kelas 3y ago
      > True, but when making an OS, assembly code is an incredibly small part of it. A few comments up this thread i briefly mentioned r/xv6 entry.S, so here’s what i meant: rv64: https://github.com/mit-pdos/xv6-riscv/blob/riscv/kernel/entry.S https://github.com/mit-pdos/xv6-riscv/blob/riscv/kernel/entr... amd64: https://github.com/dancrossnyc/rxv64/blob/main/kernel/src/entry.S https://github.com/dancrossnyc/rxv64/blob/main/kernel/src/en... > You basically need to run a few instructions to put the processor in the right mode, and you need ONE line of assembly code (often inline C) to allow usermode to call supervisor mode. Right… Please see above. Also, in riscv land we have machine, supervisor and user modes, with hypervisor mode being in the works. > When choosing an architecture for a learning OS, I think other factors would dominate, like availability of hardware (many people have a PC already, saving them $100-$200 on RISC-V hardware). yet, MIT PDOS thinks Fabrice Bellard’s ubiquitous qemu is a better, cheaper and more forgiving starting point, although i personally prefer to spend a few bucks on something as absurdly cheap and cool as kendryte k210/k510 SoC and enjoy the real deal. > Intel hate keeping tech is irrelevant [I don’t care] Yes, it’s just you. Also, it runs Minix.
astrange 3y ago
> true. technically speaking, it is long gone - any Intel CPU since about Pentium Pro is actually a well-hidden RISC, because it is more efficient. Sure that requires a pretty beefy CISC decoder in front, but the sheer power of having a virtual 8086 mode next to amd64 must totally justify all that extra TDP. It is not, the µcode on an x86 is still often "CISCy" and rightfully so - a complicated instruction like "lea" is still perfectly suited to hardware.
- adgjlsfhk1 3y ago
  this is true, but modern RISC cpus are also pretty CISCy now. The risc-V vector extension has an vfwmacc.vf which is a broadcasted vectorized widening fused multiply accumulate instruction.

by kelas 3y ago

nine_k 3y ago

I'd say that C is not elegant as a language at all. It's a good (as in "working") solution of many problems that other system languages had in late 1960s, and I'd hazard to say that the highly economical ways that were used to solve them are elegant. E.g. using #include is terrible from many angles, but is elegant as a highly minimalist way to solve the modularity problem (reduce the problem to one already solved).

kelas 3y ago
> C is not elegant okay, tastes differ, but it remains what it was in one of its original definitions: a sufficiently portable assembly. > #include hell / modularity okay, so rust has cargo, so we’re all better now, right? but what if someone will dare to argue that C has a whole bunch of cargos, some less terrible than others, if we reframe the problem like so: $ [rpm|dpkg|dnf|yum|apt|brew|pkg-add] install libcurl libcurl-dev(el) (this makes me wonder how any software even works anymore in absence of universal cargo cult, but hey)
- viraptor 3y ago
  Different things entirely. System-specific packages have no concept of C building or linking. Things work because of some agreement about paths + pkgconfig + others. This is very far from the idea of a dependency manager like cargo which is very much aware of project-specific and language features.
  - kelas 3y ago
    > Different things entirely yes, they are. > System-specific packages have no concept of C building or linking. every day i learn something new, but this time around I’m gonna go ahead a tell you that you are very mistaken. > Things work because of some agreement about paths + pkgconfig + others. True. By convention, we call it “convention”, or “standard” for short, e.g. POSIX or ISO C. Call us back once you have something like that in rustland. > This is very far from the idea of a dependency manager like cargo which is very much aware of project-specific and language features. All good and sound, and makes total sense for userland software. But what is being discussed here is an operating system and core userland. If you can imagine that to be your “project”, such as linux or OpenBSD, maybe my tongue-in-cheek comparison of a system-wide dependency manager suddenly looks less dissimilar to cargo. needless to say, things like Linux and OpenBSD will stay written in C for a little while longer. In case of BSD specifically, you can go as crazy as to bump and rebuild your entire system from source in place, kernel and userland. BSD is one pretty old cargo cult in that sense, and pretty cool, i might add. > language features right… rust 2018 edition is not really rust as of 2023, or is it? This where those pesky standards come very handy.
    - viraptor 3y ago
      > tell you that you are very mistaken. Go on then. Beyond RPMs ability to depend on soname, what else is there on the structure/installation/usage side (not on the building side which can include whatever scripts you want). Where are they now aware of the libraries more than tar.gz is?
      - kelas 3y ago
        I think I see your point. Thing is, a C program can be built and executed without that cargo dependency pyramid sandwiched into a gigantic runtime polyp. The whole operating system is your environment, and yes - if ‘man ldconfig’ is not your friend, then maybe pkg-config is, or, worse to worst, link against project-local structure, where you can indeed build the bejesus out of your imagination and ship it. That’s ok. It’s linux, after all. That’s what we do for embedded systems, anyway. I haven’t seen much success for rust in this department, although people are clearly trying to make it work. It just keeps coming out fat and ugly. A few more decades of hard push, call me a maybe. Do you know what riscv version of xv6 rev3 compiles to in terms of object size? I will not spoil it for you, but it compiles to total shreds.
- lproven 3y ago
  > a sufficiently portable assembly. No, it isn't, and it hasn't been for about 40 years. « C Is Not a Low-level Language Your computer is not a fast PDP-11. » https://queue.acm.org/detail.cfm?id=3212479 https://queue.acm.org/detail.cfm?id=3212479 David Chisnall, ACM Queue, April 30, 2018
  - kelas 3y ago
    Sounds expensive, thanks. So: Preface to the Digital Edition of Kernighan and Ritchie's The C Programming Language Oct 31, 2012 “… Remarkably, in spite of all of this change, C retains a central position. It is still the core language for operating system implementation and tool building. It remains unequaled for portability, efficiency, and ability to get close to the hardware when necessary. C has sometimes been called a high-level assembler, and this is not a bad characterization of how well it spans the range from intricate data structure and control flow to the lowest level of external devices.” (sorry, I messed up the lyrics a bit, but also I didn’t, really) Also, my computer is a fast Turing machine. And so is yours.
    - lproven 3y ago
      I can't make any sense of a single sentence of that. > Sounds expensive, thanks Huh? What does? The paper is entirely free. That's why I posted a link. Go read it. It's not very long, it's interesting, it's accessible, it's provocative and insightful and profound. > Kernighan and Ritchie Creator of C is biased about the language he created. Shock. Pictures at 11. K&R was published in 1988. Then, your PC was to some degree a fast PDP-11. That was over 1/3 of a century ago and it is no longer even remotely true. > Also, my computer is a fast Turing machine. And so is yours. Reductio ad absurdam. Here's a talk from the inventor of the Arm architecture. It's pretty good. https://www.youtube.com/watch?v=6lOnpQgn-9s https://www.youtube.com/watch?v=6lOnpQgn-9s She talks about her more recent baby, Firepath. It can, for instance, in a single opcode and a single CPU cycle load 4 separate different 32 bit integers, multiply them by 4 other 32-bit ints and store the result. (Around 25 min in but it's very worth watching the whole talk.) Her point is that C can't express stuff like this well at all. A modern CPU has dozens of execution units doing stuff in parallel, applying matrix operations and transformations to multiple different streams of data simultaneously: SIMD and MIMD combined. C has no way of even beginning to express any of this. C is no more a high-level assembly language for any 21st century CPU than a Falcon-9 reusable orbital launch vehicle is a space-going version of the Wright Flyer.

phendrenad2 3y ago

> nothing compares to booting the real xv6 on a real RISC-V system for the first time Why is that? > any Intel CPU since about Pentium Pro is actually a well-hidden RISC Well if it's well-hidden, it doesn't matter to the person learning to write an OS. ;)

kelas 3y ago
> Why is that? you said it best - the “tinkering” part is a small thing that makes all the difference when one is first led up to a computer. > if it's hidden, it doesn't matter right… and if you ignore it, maybe it’ll go away. like Intel Management Engine, perhaps. Which OS does it run, if you know? :)
- phendrenad2 3y ago
  > the “tinkering” part is a small thing that makes all the difference when one is first led up to a computer True, but when making an OS, assembly code is an incredibly small part of it. You basically need to run a few instructions to put the processor in the right mode, and you need ONE line of assembly code (often inline C) to allow usermode to call supervisor mode. When choosing an architecture for a learning OS, I think other factors would dominate, like availability of hardware (many people have a PC already, saving them $100-$200 on RISC-V hardware). > right… and if you ignore it, maybe it’ll go away. like Intel Management Engine, perhaps. Which OS does it run, if you know? :) I'm not interested in gatekeeping tech to only those who care about personal privacy, so I consider this line of thought completely irrelevant to the discussion. But that's just me...
  - kelas 3y ago
    > True, but when making an OS, assembly code is an incredibly small part of it. A few comments up this thread i briefly mentioned r/xv6 entry.S, so here’s what i meant: rv64: https://github.com/mit-pdos/xv6-riscv/blob/riscv/kernel/entry.S https://github.com/mit-pdos/xv6-riscv/blob/riscv/kernel/entr... amd64: https://github.com/dancrossnyc/rxv64/blob/main/kernel/src/entry.S https://github.com/dancrossnyc/rxv64/blob/main/kernel/src/en... > You basically need to run a few instructions to put the processor in the right mode, and you need ONE line of assembly code (often inline C) to allow usermode to call supervisor mode. Right… Please see above. Also, in riscv land we have machine, supervisor and user modes, with hypervisor mode being in the works. > When choosing an architecture for a learning OS, I think other factors would dominate, like availability of hardware (many people have a PC already, saving them $100-$200 on RISC-V hardware). yet, MIT PDOS thinks Fabrice Bellard’s ubiquitous qemu is a better, cheaper and more forgiving starting point, although i personally prefer to spend a few bucks on something as absurdly cheap and cool as kendryte k210/k510 SoC and enjoy the real deal. > Intel hate keeping tech is irrelevant [I don’t care] Yes, it’s just you. Also, it runs Minix.

astrange 3y ago

> true. technically speaking, it is long gone - any Intel CPU since about Pentium Pro is actually a well-hidden RISC, because it is more efficient. Sure that requires a pretty beefy CISC decoder in front, but the sheer power of having a virtual 8086 mode next to amd64 must totally justify all that extra TDP. It is not, the µcode on an x86 is still often "CISCy" and rightfully so - a complicated instruction like "lea" is still perfectly suited to hardware.

adgjlsfhk1 3y ago
this is true, but modern RISC cpus are also pretty CISCy now. The risc-V vector extension has an vfwmacc.vf which is a broadcasted vectorized widening fused multiply accumulate instruction.