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Autonomously Finding Performance Regressions In The Linux Kernel

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  • Autonomously Finding Performance Regressions In The Linux Kernel

    Phoronix: Autonomously Finding Performance Regressions In The Linux Kernel

    Last weekend a few Phoronix benchmarks were underway of the Linux 2.6.32-rc5 kernel when a very significant performance regression was spotted. This regression caused the PostgreSQL server to run at about 18% of the performance found in earlier kernel releases. Long story short, in tracking down this performance regression we have finally devised a way to autonomously locate performance regressions within the Linux kernel and potentially any Git-based project for that matter. Here are a few details.

    http://www.phoronix.com/vr.php?view=14285

  • #2
    Very nice, PTS is getting better and better!

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    • #3
      Amazing.
      That this thing could actually be used to do something *useful*

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      • #4
        Terrific idea!

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        • #5
          rc-5 was a dog. caused some nice fs-corruption on my /

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          • #6
            So this would be completely automatic? Meaning you could go out to lunch and not be anywhere near the machine while PTS tracks down the regression?

            Originally posted by rehabdoll View Post
            rc-5 was a dog. caused some nice fs-corruption on my /
            Seemed to happen to me in rc4 as well. I use Gentoo, and I booted up one day and my /etc/profile.env got all messed up somehow. After fixing that from a livecd, I booted up again and ended up with a hole bunch of corruption, and lost a bunch of files. Pidgin preferences, /etc/portage/package.use, some KDE configuration stuff, etc. Oh and I lost my world file, so Portage forgot all the packages I had installed.
            Last edited by pvtcupcakes; 10-22-2009, 10:26 AM.

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            • #7
              Originally posted by pvtcupcakes View Post
              So this would be completely automatic? Meaning you could go out to lunch and not be anywhere near the machine while PTS tracks down the regression?
              Yes, that is how it works in PTS Bardu 2.2.
              Michael Larabel
              http://www.michaellarabel.com/

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              • #8
                Wait, this means that if I want to have consistent data on ext4 I must look at 5x slower PostgreSQL and other write-intensive applications? And proposed solution is either obscure mount switch with possibility of occasional file corruption or really _slow_ PostgreSQL. WTF?
                Last edited by mirza; 10-22-2009, 10:52 AM.

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                • #9
                  Wow, just wow.

                  I'm no programmer, but this is an amazing piece of work. I can see this being an invaluable tool.

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                  • #10
                    Originally posted by mirza View Post
                    Wait, this means that if I want to have consistent data on ext4 I must look at 5x slower PostgreSQL and other write-intensive applications? And proposed solution is either obscure kernel switch with possibility of occasional file corruption or really _slow_ PostgreSQL. WTF?
                    I was thinking the same thing. I think I'll stick with Ext3 for now
                    (I have had Ext4 corruption before, so I simply don't trust the fs).

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                    • #11
                      Wow, this is amazing work. I wasn't paying much attention to PTS thinking big deal, so it is cool, but is it really important? But now, HELL YEAH!

                      Just the other day I was remembering something I read and thinking, while Windows and Mac has proper regression tests, who does proper regression tests in Linux? Well, step up to the plate PTS, at least for performance regressions. Yaaay!! PTS FTW.

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                      • #12
                        Very cool. I'm not working on any projects that would benefit from this directly, but I can see using this to help when I want to report bugs regarding performance regressions in mesa (or other projects).

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                        • #13
                          Originally posted by mirza View Post
                          Wait, this means that if I want to have consistent data on ext4 I must look at 5x slower PostgreSQL and other write-intensive applications? And proposed solution is either obscure mount switch with possibility of occasional file corruption or really _slow_ PostgreSQL. WTF?
                          What are you talking about? Afaik slower mode - ordered is used science 2.6.31. In 2.6.32 they're replacing some I/O related parts and maybe that's why there's such slowdown. Just wait for stable release. You've got to be kidding if you consider Ext3 is faster - afaik in some previous benchmarks Ext3 was using writeback mode (with possibility of occasional file corruption) while Ext4 was using ordered mode (really_slow_PostgreSQL, but I wonder if this is a meaningful test).

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                          • #14
                            XFS rocks!

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                            • #15
                              Originally posted by bugmenot View Post
                              Just the other day I was remembering something I read and thinking, while Windows and Mac has proper regression tests, who does proper regression tests in Linux? Well, step up to the plate PTS, at least for performance regressions. Yaaay!! PTS FTW.
                              Could you expand on your "proper regression tests" for Win and Mac?

                              Bisection is extremely powerful, but unfortunately, most people don't really know or understand it.

                              Now of course to blow you mind, IMHO, *any* unexpected change (beneficial or detremintal) are regressions. If you get an extra 20% in performance when you weren't expecting it, there is either something bad happening elsewhere - or - you hit some good Juju accidently, and you should really understand why and get some more.

                              Regards,

                              Matthew

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