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Date: Wed, 8 Feb 2017 20:05:33 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
        Chris Wright <chrisw@sous-sol.org>, Alok Kataria <akataria@vmware.com>,
        Rusty Russell <rusty@rustcorp.com.au>, Ingo Molnar <mingo@redhat.com>,
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        Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>,
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        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH 2/2] locking/mutex,rwsem: Reduce vcpu_is_preempted()
 calling frequency
Message-ID: <20170208190533.GB6515@twins.programming.kicks-ass.net>
References: <1486576825-17058-1-git-send-email-longman@redhat.com>
 <1486576825-17058-2-git-send-email-longman@redhat.com>
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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.