linux-kernel - Re: [PATCH-tip 0/2] locking/rwsem: Rwsem rearchitecture part 2 follow-up patches

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Date:   Tue, 16 Apr 2019 19:37:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        huang ying <huang.ying.caritas@...il.com>
Subject: Re: [PATCH-tip 0/2] locking/rwsem: Rwsem rearchitecture part 2
 follow-up patches

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.