From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH 0/9] qspinlock stuff -v15 Date: Mon, 30 Mar 2015 12:43:39 -0400 Message-ID: <55197D3B.4020701@hp.com> References: <20150316131613.720617163@infradead.org> <20150325194739.GK25884@l.oracle.com> <551978E8.30904@hp.com> <20150330162933.GC23123@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit 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 To: Peter Zijlstra Return-path: In-Reply-To: <20150330162933.GC23123@twins.programming.kicks-ass.net> 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 List-Id: kvm.vger.kernel.org On 03/30/2015 12:29 PM, Peter Zijlstra wrote: > 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 :-) Of course. I am just saying that the concern can be addressed with some additional code change. -Longman