Re: Scheduler patches: 6x performance increase when system is under heavy load
> Which of the 4 patches does this? I used all the 4 patches at the same time. Each patch fixes a different bug. Would you like me to try each of them individually? Were you already aware of each of these bugs? > Also, what hypervisor are you using and what does the output of booting > with "sched_debug" look like? I was running the distro in VirualBox on Fedora. Here's the info from /proc/sched_debug: https://justpaste.it/11dhb dmesg: https://justpaste.it/11dhr > Lastly, can you reproduce on real hardware? No. On real hardware, I tested in Ubuntu on an i7-4790 3.60GHz CPU without disabling HT and I saw no difference between CFS, the patched kernel and MuQSS. If I get to know a reason why one would be better than the other, I'd take the time to test it on more hardware. I'm curious how I got such a performance improvement in my VM. On Tue, Dec 13, 2016 at 8:40 AM, Peter Zijlstra wrote: > On Sun, Dec 11, 2016 at 04:41:51PM -0500, Alexandre-Xavier Labonté-Lamoureux > wrote: >> >> Here are my results (using "time make -j32" on my VM that has 4 cores): >> >> Kernel 4.8.14 >> real 26m56.151s >> user 79m52.472s >> sys 7m42.964s >> >> Same kernel, but patched: >> real 4m25.238s >> user 13m52.932s >> sys 1m25.820s >> >> I hope you guys will look into this. > > Which of the 4 patches does this? > > Also, what hypervisor are you using and what does the output of booting > with "sched_debug" look like? > > Lastly, can you reproduce on real hardware?
Scheduler patches: 6x performance increase when system is under heavy load
Hi, There's a research paper[1] called "The Linux Scheduler: a Decade of Wasted Cores". It shows how the Linux Kernel scheduler is broken and they provided fixes[2] for some of the know issues that it has. The changes are illustrated in a presentation[3] that was shown during a talk. I patched my kernel with these patches using a simple tool[4]. I compiled the Linux kernel on it and I was flabbergasted to see an estimated six times performance increase. It was blazing fast and I couldn't believe it. Here are my results (using "time make -j32" on my VM that has 4 cores): Kernel 4.8.14 real 26m56.151s user 79m52.472s sys 7m42.964s Same kernel, but patched: real 4m25.238s user 13m52.932s sys 1m25.820s I hope you guys will look into this. If these changes were introduced into the kernel, it would be great and benefit to a lot of people. There may be some regression. People have said that it improved the throughput of the kernel, but on some application such as games, there are some performance spikes due to overscheduling. This already happens in the vanilla kernel, but it's worsened a bit. Power management will also be a thing to look into. I hope the scheduler engineers will fix the kernel. The research paper has been out for a while and nothing has been done yet. Personally, I think six times is huge as someone who compiles huge projects often and the regressions if any are not apparent to me. Other people should try it too to test if it's good. Regards, Alexandre-Xavier Labonté-Lamoureux [1] https://www.ece.ubc.ca/~sasha/papers/eurosys16-final29.pdf [2] https://github.com/Freeaqingme/wastedcores/tree/linux-4.5/patches [3] http://www.i3s.unice.fr/~jplozi/wastedcores/files/extended_talk.pdf [4] https://github.com/Turbine1991/build_ubuntu_kernel_wastedcores
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