Messages in this thread | | | Date | Wed, 17 Apr 2019 07:57:45 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH-tip 0/2] locking/rwsem: Rwsem rearchitecture part 2 follow-up patches |
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* Waiman Long <longman@redhat.com> wrote:
> On 04/16/2019 01:37 PM, Peter Zijlstra wrote: > > On Tue, Apr 16, 2019 at 01:03:10PM -0400, Waiman Long wrote: > >> On 04/16/2019 10:17 AM, Peter Zijlstra wrote: > >>> On Tue, Apr 16, 2019 at 09:18:50AM -0400, Waiman Long wrote: > >>>> On 04/16/2019 09:10 AM, Peter Zijlstra wrote: > >>>>> On Mon, Apr 15, 2019 at 04:58:27PM -0400, Waiman Long wrote: > >>>>>> This series contain 2 follow-up patches to alleviate the performance > >>>>>> regression found in the page_fault1 test of the will-it-scale benchmark. > >>>>>> This does not recover all the lost performance, but reclaim a sizeable > >>>>>> portion of it. > >>>>>> > >>>>>> The regression was found on an Intel system. I have run the test on > >>>>>> an AMD system. The regression wasn't seen there. There are only minor > >>>>>> variations in performance. Perhaps the page fault path is quite different > >>>>>> between Intel and AMD systems. > >>>>> Can you please just fold this back into the appropriate patches? Trying > >>>>> to review all the back and forth is painful. > >>>> I will send out an update part 2 patch with patch 1 of this series > >>>> merged into the writer spinning on reader patch. Patch 2 of this series > >>>> will be a standalone one. > >>> Hmm, in that case I can fold it back too. So hold off on sending it. > >>> > >>> I thought #2 was a fixup for an earlier patch as well. > >> #2 is a performance fix. > > Of this patch? > > > > 206038 N T Apr 13 Waiman Long (7.5K) ├─>[PATCH v4 11/16] locking/rwsem: Enable readers spinning on writer > > > > Fixes should have a Fixes: tag. And if the patch it fixes isn't a commit > > yet, the patch should be refreshed to not need a fix. > > The original patch isn't wrong. This patch just introduce another idea > to make it better. That is why I would still like to separate it as a > distinct patch.
Yeah, I think it's better to have it in two separate patches. Basically patch #1 has a downside for certain workloads, which the heuristics in patch #2 improve. That's the only connection between the two patches.
If we find some other worst-case workload then the split of the commits would allow more finegrained examination of the effects of these performance tunings.
Thanks,
Ingo
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