From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org,
Pan Xinhui <xinhui@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>
Subject: Re: [PATCH v2] locking/pvqspinlock: Relax cmpxchg's to improve performance on some archs
Date: Tue, 3 Jan 2017 17:18:36 +0100 [thread overview]
Message-ID: <20170103161836.GY3107@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1482697561-23848-1-git-send-email-longman@redhat.com>
On Sun, Dec 25, 2016 at 03:26:01PM -0500, Waiman Long wrote:
> A number of cmpxchg calls in qspinlock_paravirt.h were replaced by more
> relaxed versions to improve performance on architectures that use LL/SC.
Claim without numbers ;-)
>
> All the locking related cmpxchg's are replaced with the _acquire
> variants:
> - pv_queued_spin_steal_lock()
> - trylock_clear_pending()
So these seem to make sense in that they're in 'fast' paths..
> The cmpxchg's related to hashing are replaced by either by the _release
> or the _relaxed variants. See the inline comment for details.
But these not so much, we're going to put the vcpu to sleep, why does it
make sense to 'optimize' the wait/kick stuff?
next prev parent reply other threads:[~2017-01-03 16:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-25 20:26 Waiman Long
2016-12-26 5:50 ` Boqun Feng
2017-01-03 22:23 ` Waiman Long
2017-01-03 16:18 ` Peter Zijlstra [this message]
2017-01-03 22:07 ` Waiman Long
2017-01-04 9:41 ` Peter Zijlstra
2017-01-05 8:16 ` Pan Xinhui
2017-01-05 9:48 ` Peter Zijlstra
2017-01-05 9:51 ` Boqun Feng
2017-01-05 15:17 ` Waiman Long
2017-01-05 15:40 ` Boqun Feng
2017-01-05 15:30 ` Waiman Long
[not found] ` <CAH4ORazqsCBA4G5paHtsp8PMfM=J3P6rvyR-53-ZLjn=7U6J0g@mail.gmail.com>
2017-02-08 4:05 ` Boqun Feng
2017-02-08 6:09 ` Boqun Feng
2017-02-08 6:47 ` Pan Xinhui
2017-02-08 6:48 ` Pan Xinhui
2017-02-08 7:09 ` Pan Xinhui
2017-02-08 7:15 ` Boqun Feng
[not found] ` <778926a5-cf9f-586b-6bc4-b9453d88aabb@redhat.com>
2017-02-13 2:24 ` panxinhui
2017-02-13 3:19 ` Boqun Feng
2017-02-17 19:01 ` Waiman Long
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