Messages in this thread | | | Date | Mon, 27 Jul 2020 12:52:42 +0200 | From | Jan Kara <> | Subject | Re: [fsnotify] c738fbabb0: will-it-scale.per_process_ops -9.5% regression |
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On Sun 26-07-20 14:52:47, Amir Goldstein wrote: > On Fri, Jul 24, 2020 at 6:47 AM Amir Goldstein <amir73il@gmail.com> wrote: > > > > On Fri, Jul 24, 2020 at 5:45 AM Rong Chen <rong.a.chen@intel.com> wrote: > > > > > > > > > > > > On 7/21/20 11:59 PM, Amir Goldstein wrote: > > > > On Tue, Jul 21, 2020 at 3:15 AM kernel test robot <rong.a.chen@intel.com> wrote: > > > >> Greeting, > > > >> > > > >> FYI, we noticed a -9.5% regression of will-it-scale.per_process_ops due to commit: > > > >> > > > >> > > > >> commit: c738fbabb0ff62d0f9a9572e56e65d05a1b34c6a ("fsnotify: fold fsnotify() call into fsnotify_parent()") > > > > Strange, that's a pretty dumb patch moving some inlined code from one > > > > function to > > > > another (assuming there are no fsnotify marks in this test). > > > > > > > > Unless I am missing something the only thing that changes slightly is > > > > an extra d_inode(file->f_path.dentry) deference. > > > > I can get rid of it. > > > > > > > > Is it possible to ask for a re-test with fix patch (attached)? > > > > > > Hi Amir, > > > > > > We failed to apply this patch, could you tell us the base commit or the > > > base branch? > > > > > > > Hi Rong, > > > > The patch is applied on top of the reported offending commit: > > c738fbabb0ff62d0f9a9572e56e65d05a1b34c6a ("fsnotify: fold fsnotify() > > call into fsnotify_parent()") > > > > I pushed it to my github: > > https://github.com/amir73il/linux/commits/for_lkp > > > > FWIW, I tried reproducing the reported regression on a local machine. > > I ran the test twice on each of the branch commits: > > 26dc3d2bff62 fsnotify: pass inode to fsnotify_parent() > c738fbabb0ff fsnotify: fold fsnotify() call into fsnotify_parent() > 71d734103edf fsnotify: Rearrange fast path to minimise overhead when > there is no watcher > 47aaabdedf36 fanotify: Avoid softlockups when reading many events > > Not only did I not observe a regression with the reported commit, > but there was a slight improvement. And then there yet was another > improvement with the fix commit on top of it.
I suspect this may be closely related to code generation, code cacheline alignment etc. and thus depends heavily on a particular compiler version and CPU. I've checked the commit myself and I agree it looks innocent so for these reasons, I'm not particularly worried about this regression.
Honza -- Jan Kara <jack@suse.com> SUSE Labs, CR
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