From: Peter Zijlstra <peterz@infradead.org>
To: Peter Xu <peterx@redhat.com>
Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Radim Kr??m???? <rkrcmar@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] sched/swait: allow swake_up() to return
Date: Fri, 10 Nov 2017 09:05:20 +0100 [thread overview]
Message-ID: <20171110080520.uslq75uucwlg5y7y@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20171110071017.GH20627@xz-mi>
On Fri, Nov 10, 2017 at 03:10:17PM +0800, Peter Xu wrote:
> I came to this when reading kvm_vcpu_wake_up(), so that only affects
> some statistic which may not be that critical. However I don't know
> whether there would be any other real use case that we would like to
> know exactly whether a call to [s]wake_up() has really done something
> or just returned with a NOP.
>
> Anyway, please let me know if you think the same change to wake_up()
> would be meaningful, otherwise I can drop this patch and post another
> KVM-only one to clean up the redundant callers of swait_active(),
> since even if we dropped that list check in 35a2897c2a30, we'll do
> that again in swake_up_locked().
See commits:
8cd641e3c7cb ("sched/wait: Add swq_has_sleeper()")
5e0018b3e39e ("kvm: Serialize wq active checks in kvm_vcpu_wake_up()")
In any case, I don't think we want the change you propose. The numbers
don't mean much and there's no point in making all the callers in the
kernel slower for it.
next prev parent reply other threads:[~2017-11-10 8:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20171109091854.24367-1-peterx@redhat.com>
2017-11-09 9:18 ` [PATCH 1/2] sched/swait: allow swake_up() to return Peter Xu
2017-11-09 10:06 ` Paolo Bonzini
2017-11-10 7:12 ` Peter Xu
2017-11-09 10:23 ` Peter Zijlstra
2017-11-10 7:10 ` Peter Xu
2017-11-10 8:05 ` Peter Zijlstra [this message]
2017-11-13 3:33 ` Peter Xu
2017-11-13 5:19 ` Peter Xu
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