From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/2] locking/mutex,rwsem: Reduce vcpu_is_preempted()
	calling frequency
Date: Wed, 8 Feb 2017 20:05:33 +0100
Message-ID: <20170208190533.GB6515@twins.programming.kicks-ass.net>
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Cc: linux-arch@vger.kernel.org, Juergen Gross <jgross@suse.com>,
	Jeremy Fitzhardinge <jeremy@goop.org>, x86@kernel.org, kvm@vger.kernel.org,
	Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>,
	Paolo Bonzini <pbonzini@redhat.com>, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	Chris Wright <chrisw@sous-sol.org>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	xen-devel@lists.xenproject.org, Alok Kataria <akataria@vmware.com>,
	Thomas Gleixner <tglx@linutronix.de>
To: Waiman Long <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.