Messages in this thread Patch in this message | | | Date | Mon, 6 Jan 2020 23:52:12 +0800 | From | Feng Tang <> | Subject | Re: [LKP] [cpuidle] 259231a045: will-it-scale.per_process_ops -12.6% regression |
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Hi Marcelo,
On Fri, Jan 03, 2020 at 10:36:14AM -0300, Marcelo Tosatti wrote: > Hi Feng, > > > Anyway, I found commit 259231a04 lost one "break" when moving > > the original code, thus the semantics is changed to the last > > enabled state's target_residency instead of the first enabled > > one's. > > > > I don't know if it's intentional, and I guess no, so here > > is a fix patch, please review, thanks > > Not intentional. > > > But even with this patch, the regression is still not recovered. > > > > - Feng > > This has been fixed upstream already, should be on Rafael's GIT tree.
Glad to hear that.
> > > >From cddd6b409e18ce97a8d7b851db4400396f71d857 Mon Sep 17 00:00:00 2001 > > From: Feng Tang <feng.tang@intel.com> > > Date: Thu, 2 Jan 2020 16:58:31 +0800 > > Subject: [PATCH] cpuidle: Add back the lost break in cpuidle_poll_time > > > > Commit c4cbb8b649b5 move the poll time calculation into a > > new function cpuidle_poll_time(), during which one "break" > > get lost, and the semantic is changed from the last enabled > > state's target_residency instead of the first enabled one's. > > > > So add it back. > > > > Fixes: c4cbb8b649b5 "cpuidle: add poll_limit_ns to cpuidle_device structure" > > Signed-off-by: Feng Tang <feng.tang@intel.com> > > Cc: Marcelo Tosatti <mtosatti@redhat.com> > > --- > > drivers/cpuidle/cpuidle.c | 1 + > > 1 file changed, 1 insertion(+) > > About the regression... if you only revert the > > drivers/cpuidle/poll_state.c > > changes from > > 259231a045616c4101d023a8f4dcc8379af265a6 > > Is the performance regression gone?
Aha, I did tried a similar patch, which can NOT cure the regression.
(You can check if the below patch complies with your idea)
Another thing I've tried is to move the "poll_limit_ns" to the end of struct cpuidle_device which could reduce the regression from 12.6% to about 7.5%
Thanks, Feng
commit 18260c38f4a802592e1cb6e82eb71ddca7709def Author: Feng Tang <feng.tang@intel.com> Date: Fri Jan 3 09:21:54 2020 +0800
make the poll_time inline
Signed-off-by: Feng Tang <feng.tang@intel.com>
diff --git a/drivers/cpuidle/poll_state.c b/drivers/cpuidle/poll_state.c index c8fa5f4..e278d9e 100644 --- a/drivers/cpuidle/poll_state.c +++ b/drivers/cpuidle/poll_state.c @@ -22,7 +22,24 @@ static int __cpuidle poll_idle(struct cpuidle_device *dev, unsigned int loop_count = 0; u64 limit; - limit = cpuidle_poll_time(drv, dev); + + if (likely(dev->poll_limit_ns)) + limit = dev->poll_limit_ns; + else { + int i; + + limit = TICK_NSEC; + for (i = 1; i < drv->state_count; i++) { + if (drv->states[i].disabled || dev->states_usage[i].disable) + continue; + + limit = (u64)drv->states[i].target_residency * NSEC_PER_USEC; + break; + } + + dev->poll_limit_ns = limit; + } + while (!need_resched()) { cpu_relax();
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