linux-kernel - Re: [PATCH-tip v3 02/14] locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON

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Date:   Fri, 12 Apr 2019 14:05:50 -0400
From:   Waiman Long <longman@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        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 v3 02/14] locking/rwsem: Make owner available even if
 !CONFIG_RWSEM_SPIN_ON_OWNER

On 04/12/2019 12:41 PM, Ingo Molnar wrote:
> * Waiman Long <longman@...hat.com> wrote:
>
>>> BTW, the v3 patch that I posted yesterday should work fine as long as
>>> CONFIG_RWSEM_SPIN_ON_OWNER is defined.
>>>
>>> Cheers,
>>> Longman
>>>
>> Oh, I see that the WIP.locking/core is currently merged into master. I
>> would say rwsem part1 patchset and patch 1 of part2 are stable. So I
>> would suggest merging those into the the master will be good. The rests
>> are still under review until I get an OK from Peter. If they miss the
>> next merge window and have to postpone to 5.3, I am fine with that.
> So beyond the primary constraint of PeterZ OK-ing it all, there's also 
> these two scalability regression reports from the ktest bot:
>
>  [locking/rwsem] 1b94536f2d: stress-ng.bad-altstack.ops_per_sec -32.7% regression

A regression due to the lock handoff patch is kind of expected, but I
will into why there is such a large drop.

>  [locking/rwsem] adc32e8877: will-it-scale.per_thread_ops -21.0% regression

Will look into that also.

Thanks,
Longman