From: Ingo Molnar <mingo@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
huang ying <huang.ying.caritas@gmail.com>
Subject: Re: [PATCH-tip v3 02/14] locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON_OWNER
Date: Tue, 16 Apr 2019 09:53:13 +0200 [thread overview]
Message-ID: <20190416075313.GA34215@gmail.com> (raw)
In-Reply-To: <d012c68e-4c43-04af-3505-4c980e2d00a5@redhat.com>
* Waiman Long <longman@redhat.com> wrote:
> > It can be seen that a lot more readers got the lock via optimistic
> > spinning. One possibility is that reader optimistic spinning causes
> > readers to spread out into more lock acquisition groups than without. The
> > K3 results show that grouping more readers into one lock acquisition
> > group help to improve performance for this microbenchmark. I will need
> > to run more tests to find out the root cause of this regression. It is
> > not an easy problem to solve.
>
> Just an update on my will-it-scale regression investigation. I have
> tried various ways to tune the rwsem code to get more performance out
> from this benchmark. I got some minor improvements but nothing major. So
> it looks like that there are some workloads that have performance hurted
> by reader optimistic spinning and this benchmark is one of them. Now I
> am testing an adaptive reader optimistic spinning disabling patch that
> shows great promise as I was able to bring back a major portion of the
> lost performance. I will try to make the patch more aggressive to see if
> it can bring most of the lost performance back.
Thank you!
I've applied your two latest patches to WIP.locking/core as well, to keep
it all tested and to see whether there's any other regressions. It's all
looking good so far in my dogfood testing.
Thanks,
Ingo
next prev parent reply other threads:[~2019-04-16 7:53 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 18:42 [PATCH-tip v3 00/14] locking/rwsem: Rwsem rearchitecture part 2 Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 01/14] locking/rwsem: Prevent unneeded warning during locking selftest Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 02/14] locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON_OWNER Waiman Long
2019-04-11 8:12 ` Peter Zijlstra
2019-04-11 16:03 ` Waiman Long
2019-04-12 7:02 ` Ingo Molnar
2019-04-12 7:05 ` Peter Zijlstra
2019-04-12 7:09 ` Ingo Molnar
2019-04-12 14:04 ` Waiman Long
2019-04-12 14:07 ` Waiman Long
2019-04-12 14:22 ` Waiman Long
2019-04-12 16:41 ` Ingo Molnar
2019-04-12 18:05 ` Waiman Long
2019-04-13 2:24 ` Waiman Long
2019-04-15 13:43 ` Waiman Long
2019-04-16 7:53 ` Ingo Molnar [this message]
2019-04-12 18:21 ` Peter Zijlstra
2019-04-10 18:42 ` [PATCH-tip v3 03/14] locking/rwsem: Implement a new locking scheme Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 04/14] locking/rwsem: Implement lock handoff to prevent lock starvation Waiman Long
2019-04-10 19:38 ` Peter Zijlstra
2019-04-10 20:28 ` Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 05/14] locking/rwsem: Remove rwsem_wake() wakeup optimization Waiman Long
2019-04-11 7:25 ` Peter Zijlstra
2019-04-11 15:55 ` Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 06/14] locking/rwsem: Make rwsem_spin_on_owner() return owner state Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 07/14] locking/rwsem: Ensure an RT task will not spin on reader Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 08/14] locking/rwsem: Wake up almost all readers in wait queue Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 09/14] locking/rwsem: Enable readers spinning on writer Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 10/14] locking/rwsem: Enable time-based spinning on reader-owned rwsem Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 11/14] locking/rwsem: Add more rwsem owner access helpers Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 12/14] locking/rwsem: Guard against making count negative Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 13/14] locking/rwsem: Merge owner into count on x86-64 Waiman Long
2019-04-10 18:42 ` [PATCH-tip v3 14/14] locking/rwsem: Remove redundant computation of writer lock word Waiman Long
2019-04-11 8:37 ` [PATCH-tip v3 00/14] locking/rwsem: Rwsem rearchitecture part 2 Peter Zijlstra
2019-04-11 16:09 ` Waiman Long
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