Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755088AbbGCMTV (ORCPT ); Fri, 3 Jul 2015 08:19:21 -0400 Received: from casper.infradead.org ([85.118.1.10]:55089 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755003AbbGCMTM (ORCPT ); Fri, 3 Jul 2015 08:19:12 -0400 Date: Fri, 3 Jul 2015 14:19:07 +0200 From: Peter Zijlstra To: Paolo Bonzini Cc: Pontus Fuchs , Linus Torvalds , mingo@redhat.com, "linux-kernel@vger.kernel.org" , gleb@kernel.org Subject: Re: [PATCH] sched,kvm: Fix KVM preempt_notifier usage Message-ID: <20150703121907.GH19282@twins.programming.kicks-ass.net> References: <558BED42.1030000@gmail.com> <20150625120949.GZ3644@twins.programming.kicks-ass.net> <558BF0E4.50602@gmail.com> <20150625125514.GA3644@twins.programming.kicks-ass.net> <55966E0B.7060100@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55966E0B.7060100@redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 736 Lines: 14 On Fri, Jul 03, 2015 at 01:12:11PM +0200, Paolo Bonzini wrote: > In fact you shouldn't have just tested the patch on a case _without_ > preemption notifiers, you should have also benchmarked the impact that > static keys have _with_ preemption notifiers. In a > not-really-artificial case (one single-processor guest running on the > host), the static key patch adds a static_key_slow_inc on a relatively > hot path for KVM, which is not acceptable. Spawning the first vcpu is a hot path? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/