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 13:03:10 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 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.

Cheers,
Longman