From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 0/9] qspinlock stuff -v15 Date: Mon, 30 Mar 2015 18:29:33 +0200 Message-ID: <20150330162933.GC23123@twins.programming.kicks-ass.net> References: <20150316131613.720617163@infradead.org> <20150325194739.GK25884@l.oracle.com> <551978E8.30904@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <551978E8.30904@hp.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Waiman Long Cc: linux-arch@vger.kernel.org, riel@redhat.com, x86@kernel.org, kvm@vger.kernel.org, Konrad Rzeszutek Wilk , scott.norton@hp.com, raghavendra.kt@linux.vnet.ibm.com, paolo.bonzini@gmail.com, oleg@redhat.com, linux-kernel@vger.kernel.org, mingo@redhat.com, david.vrabel@citrix.com, hpa@zytor.com, luto@amacapital.net, xen-devel@lists.xenproject.org, tglx@linutronix.de, paulmck@linux.vnet.ibm.com, torvalds@linux-foundation.org, boris.ostrovsky@oracle.com, virtualization@lists.linux-foundation.org, doug.hatch@hp.com List-Id: linux-arch.vger.kernel.org On Mon, Mar 30, 2015 at 12:25:12PM -0400, Waiman Long wrote: > I did it differently in my PV portion of the qspinlock patch. Instead of > just waking up the CPU, the new lock holder will check if the new queue head > has been halted. If so, it will set the slowpath flag for the halted queue > head in the lock so as to wake it up at unlock time. This should eliminate > your concern of dong twice as many VMEXIT in an overcommitted scenario. We can still do that on top of all this right? As you might have realized I'm a fan of gradual complexity :-) From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from casper.infradead.org ([85.118.1.10]:35331 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751398AbbC3Q3s (ORCPT ); Mon, 30 Mar 2015 12:29:48 -0400 Date: Mon, 30 Mar 2015 18:29:33 +0200 From: Peter Zijlstra Subject: Re: [PATCH 0/9] qspinlock stuff -v15 Message-ID: <20150330162933.GC23123@twins.programming.kicks-ass.net> References: <20150316131613.720617163@infradead.org> <20150325194739.GK25884@l.oracle.com> <551978E8.30904@hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <551978E8.30904@hp.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Waiman Long Cc: Konrad Rzeszutek Wilk , tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, paolo.bonzini@gmail.com, boris.ostrovsky@oracle.com, paulmck@linux.vnet.ibm.com, riel@redhat.com, torvalds@linux-foundation.org, raghavendra.kt@linux.vnet.ibm.com, david.vrabel@citrix.com, oleg@redhat.com, scott.norton@hp.com, doug.hatch@hp.com, linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, luto@amacapital.net Message-ID: <20150330162933.RQm2E8sigkIQM4XIL7xPozbokJpb3EhRoouSQWTPbkk@z> On Mon, Mar 30, 2015 at 12:25:12PM -0400, Waiman Long wrote: > I did it differently in my PV portion of the qspinlock patch. Instead of > just waking up the CPU, the new lock holder will check if the new queue head > has been halted. If so, it will set the slowpath flag for the halted queue > head in the lock so as to wake it up at unlock time. This should eliminate > your concern of dong twice as many VMEXIT in an overcommitted scenario. We can still do that on top of all this right? As you might have realized I'm a fan of gradual complexity :-)