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The main feature I'm looking forward to is zswap in kernel 3.11 [1]. Basically instead of swapping, the kernel will first compress infrequently used pages in R

by csense 13y ago

The main feature I'm looking forward to is zswap in kernel 3.11 [1]. Basically instead of swapping, the kernel will first compress infrequently used pages in RAM, which is orders of magnitude faster than swapping to disk. The practical effect of this is basically the same as a free RAM upgrade! [1] https://lwn.net/Articles/537422/ https://lwn.net/Articles/537422/

giovannibajo1 13y ago
Mavericks has the same feature, curious they're both shipping at the same time
- yapcguy 13y ago
  I guess we'll never know if Apple engineers were "inspired" by Zram and Zswap Linux development. I don't think anything like this is available in Freebsd yet. http://lists.freebsd.org/pipermail/freebsd-performance/2012-November/004650.html http://lists.freebsd.org/pipermail/freebsd-performance/2012-...
  - neilc 13y ago
    There have been countless research papers on this topic, so I doubt it -- http://scholar.google.com/scholar?hl=en&q=dynamic+memory+compression+swap&btnG=&as_sdt=1%2C5&as_sdtp= http://scholar.google.com/scholar?hl=en&q=dynamic+memory+com.... Not to mention the fact that RAM compression was quite common back in the DOS/Win95 days: http://oreilly.com/centers/windows/feat/softram/dblscan.html http://oreilly.com/centers/windows/feat/softram/dblscan.html
    - giovannibajo1 13y ago
      Yes, and that's exactly what makes it curious. It's a technology who's always been "known", but no modern operating system has bothered implementing it. Now we got two major OS shipping it at the same time, and I can't even see a correlation with a change of hardware (i.e. i can't see RAM being lately more scarce on PCs or Macs to the point of making this feature more useful than, say, 2 years ago, or 4 years ago, or 6 years ago).
      - vidarh 13y ago
        I think it's the opposite (that it is at least in part more RAM that is driving this) If you're going to end up swapping to disk most of the time anyway, the feature doesn't seem to be very useful. But with much faster CPUs, "many core" CPUs where your apps often won't manage to take advantage of the CPUs, and cheap RAM making lots of people buy huge amounts, the "cost" of using compression to offset swapping to disk seems to have dropped substantially, and the chance of avoiding swapping to disk entirely seems to have increased.
X4 13y ago
You mean zram, right? I've been using that for months on Gentoo, it gave me about 10% speedup. Maybe you already have it available too, try: $ sudo modprobe zram
- csense 13y ago
  No, I don't mean zram. See ava1ar's answer to this stackoverflow question: http://stackoverflow.com/questions/18437205/difference-between-zram-and-zswap http://stackoverflow.com/questions/18437205/difference-betwe... The big differences are (a) zswap is in mainline, zram is not, (b) zswap can swap pages out to disk when it's full, zram cannot. Also, I wouldn't really characterize the difference that zswap makes as a constant, workload-independent percentage performance boost. Rather, it increases the amount of RAM you can use before the system moves from the "acceptable performance" regime (minimal swapping) to the "dismal performance" regime (lots of swapping). For things like running Rails apps on a relatively small VPS, or getting the most out of a limited-RAM machine like an Eee PC or Raspberry Pi, this is very important.
JSno 13y ago
For programmers or IT related people, you can easily compile kernel 3.12 with in 10 commands. and reboot.It will give you latest kernel. 1. install git. 2. get linux kernel from Linus tree. 3. google how to compile kernel and compile it. 4. restart. Note: ubuntu will elegantly handle GRUB2 for you. That means when you reboot, you are able to choose what kernel you want to use. Try this, and you won't need to wait for UBuntu 13.XX 14.XX for new kernel you want to use.
- dchichkov 13y ago
  Not so fast. Desktop versions of new Ubuntu distros all require 3d support. And you can easily run into an obscure problem [1] that would have you reconfiguring graphics for a half a day and result in an unusable system, even if you'd try to go back to an old kernel. [1] an example: https://bugs.freedesktop.org/show_bug.cgi?id=69928 https://bugs.freedesktop.org/show_bug.cgi?id=69928
epsylon 13y ago
Basically, we'll soon be able to download more RAM!
fulafel 13y ago
The compression feature is in 12.04 LTS too. http://packages.ubuntu.com/precise/zram-config http://packages.ubuntu.com/precise/zram-config

by csense 13y ago

giovannibajo1 13y ago

Mavericks has the same feature, curious they're both shipping at the same time

yapcguy 13y ago
I guess we'll never know if Apple engineers were "inspired" by Zram and Zswap Linux development. I don't think anything like this is available in Freebsd yet. http://lists.freebsd.org/pipermail/freebsd-performance/2012-November/004650.html http://lists.freebsd.org/pipermail/freebsd-performance/2012-...
- neilc 13y ago
  There have been countless research papers on this topic, so I doubt it -- http://scholar.google.com/scholar?hl=en&q=dynamic+memory+compression+swap&btnG=&as_sdt=1%2C5&as_sdtp= http://scholar.google.com/scholar?hl=en&q=dynamic+memory+com.... Not to mention the fact that RAM compression was quite common back in the DOS/Win95 days: http://oreilly.com/centers/windows/feat/softram/dblscan.html http://oreilly.com/centers/windows/feat/softram/dblscan.html
  - giovannibajo1 13y ago
    Yes, and that's exactly what makes it curious. It's a technology who's always been "known", but no modern operating system has bothered implementing it. Now we got two major OS shipping it at the same time, and I can't even see a correlation with a change of hardware (i.e. i can't see RAM being lately more scarce on PCs or Macs to the point of making this feature more useful than, say, 2 years ago, or 4 years ago, or 6 years ago).
    - vidarh 13y ago
      I think it's the opposite (that it is at least in part more RAM that is driving this) If you're going to end up swapping to disk most of the time anyway, the feature doesn't seem to be very useful. But with much faster CPUs, "many core" CPUs where your apps often won't manage to take advantage of the CPUs, and cheap RAM making lots of people buy huge amounts, the "cost" of using compression to offset swapping to disk seems to have dropped substantially, and the chance of avoiding swapping to disk entirely seems to have increased.

X4 13y ago

You mean zram, right? I've been using that for months on Gentoo, it gave me about 10% speedup. Maybe you already have it available too, try: $ sudo modprobe zram

csense 13y ago
No, I don't mean zram. See ava1ar's answer to this stackoverflow question: http://stackoverflow.com/questions/18437205/difference-between-zram-and-zswap http://stackoverflow.com/questions/18437205/difference-betwe... The big differences are (a) zswap is in mainline, zram is not, (b) zswap can swap pages out to disk when it's full, zram cannot. Also, I wouldn't really characterize the difference that zswap makes as a constant, workload-independent percentage performance boost. Rather, it increases the amount of RAM you can use before the system moves from the "acceptable performance" regime (minimal swapping) to the "dismal performance" regime (lots of swapping). For things like running Rails apps on a relatively small VPS, or getting the most out of a limited-RAM machine like an Eee PC or Raspberry Pi, this is very important.

JSno 13y ago

For programmers or IT related people, you can easily compile kernel 3.12 with in 10 commands. and reboot.It will give you latest kernel. 1. install git. 2. get linux kernel from Linus tree. 3. google how to compile kernel and compile it. 4. restart. Note: ubuntu will elegantly handle GRUB2 for you. That means when you reboot, you are able to choose what kernel you want to use. Try this, and you won't need to wait for UBuntu 13.XX 14.XX for new kernel you want to use.

dchichkov 13y ago
Not so fast. Desktop versions of new Ubuntu distros all require 3d support. And you can easily run into an obscure problem [1] that would have you reconfiguring graphics for a half a day and result in an unusable system, even if you'd try to go back to an old kernel. [1] an example: https://bugs.freedesktop.org/show_bug.cgi?id=69928 https://bugs.freedesktop.org/show_bug.cgi?id=69928

epsylon 13y ago

Basically, we'll soon be able to download more RAM!

fulafel 13y ago

The compression feature is in 12.04 LTS too. http://packages.ubuntu.com/precise/zram-config http://packages.ubuntu.com/precise/zram-config