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Subject: Re: [PATCH 2/2] locking/mutex,rwsem: Reduce vcpu_is_preempted()
 calling frequency
To: Peter Zijlstra <peterz@infradead.org>
References: <1486576825-17058-1-git-send-email-longman@redhat.com>
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Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
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From: Waiman Long <longman@redhat.com>
Organization: Red Hat
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Date: Wed, 8 Feb 2017 14:09:26 -0500
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On 02/08/2017 02:05 PM, Peter Zijlstra wrote:
> On Wed, Feb 08, 2017 at 01:00:25PM -0500, Waiman Long wrote:
>> As the vcpu_is_preempted() call is pretty costly compared with other
>> checks within mutex_spin_on_owner() and rwsem_spin_on_owner(), they
>> are done at a reduce frequency of once every 256 iterations.
> That's just disgusting.

I do have some doubt myself on the effectiveness of this patch. Anyway,
it is the first patch that I think is more beneficial.

Cheers,
Longman