From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, mingo@redhat.com,
dave@stgolabs.net, will.deacon@arm.com, Waiman.Long@hpe.com,
benh@kernel.crashing.org
Subject: Re: [PATCH] locking/osq: Drop the overload of osq lock
Date: Sat, 25 Jun 2016 18:15:40 +0200 [thread overview]
Message-ID: <20160625161540.GM30154@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160625152130.GA2452@insomnia>
On Sat, Jun 25, 2016 at 11:21:30PM +0800, Boqun Feng wrote:
> So on PPC, we have lppaca::yield_count to detect when an vcpu is
> preempted, if the yield_count is even, the vcpu is running, otherwise it
> is preempted(__spin_yield() is a user of this).
>
> Therefore it makes more sense we
>
> if (need_resched() || vcpu_is_preempted(old))
>
> here, and implement vcpu_is_preempted() on PPC as
>
> bool vcpu_is_preempted(int cpu)
> {
> return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1)
> }
>
> Thoughts?
Would that not have issues where the owner cpu is kept running but the
spinner (ie. _this_ vcpu) gets preempted? I would think that in that
case we too want to stop spinning.
Although, if all vcpus are scheduled equal, it might not matter on
average.
next prev parent reply other threads:[~2016-06-25 16:15 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-25 17:42 Pan Xinhui
2016-06-25 14:24 ` Peter Zijlstra
2016-06-25 15:21 ` Boqun Feng
2016-06-25 16:09 ` Peter Zijlstra
2016-06-25 16:13 ` Peter Zijlstra
2016-06-25 17:27 ` panxinhui
2016-06-25 19:12 ` Peter Zijlstra
2016-06-26 4:59 ` panxinhui
2016-06-27 7:55 ` Peter Zijlstra
2016-06-27 10:19 ` xinhui
2016-06-25 16:28 ` Boqun Feng
2016-06-25 18:28 ` Peter Zijlstra
2016-06-25 16:15 ` Peter Zijlstra [this message]
2016-06-25 16:45 ` Boqun Feng
2016-06-25 17:27 ` panxinhui
2016-06-25 19:20 ` Peter Zijlstra
2016-06-25 19:29 ` Peter Zijlstra
2016-06-26 2:26 ` Boqun Feng
2016-06-26 5:21 ` panxinhui
2016-06-26 6:10 ` Boqun Feng
2016-06-26 6:58 ` panxinhui
2016-06-26 14:11 ` Boqun Feng
2016-06-26 15:54 ` panxinhui
2016-06-26 6:59 ` Boqun Feng
2016-06-26 7:08 ` panxinhui
2016-06-26 14:29 ` Boqun Feng
2016-06-26 15:11 ` panxinhui
2016-06-27 6:45 ` Boqun Feng
2016-06-27 7:36 ` xinhui
2016-06-27 8:09 ` Peter Zijlstra
2016-06-27 10:31 ` Boqun Feng
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