From mboxrd@z Thu Jan 1 00:00:00 1970 From: Srivatsa Vaddagiri Subject: Re: [RFC PATCH 2/3] sched: add yield_to function Date: Fri, 3 Dec 2010 22:59:54 +0530 Message-ID: <20101203172954.GC11725@linux.vnet.ibm.com> References: <20101202144129.4357fe00@annuminas.surriel.com> <20101202144423.3ad1908d@annuminas.surriel.com> <1291355656.7633.124.camel@marge.simson.net> <20101203134618.GG27994@linux.vnet.ibm.com> <1291387511.7992.15.camel@marge.simson.net> <4CF90341.4020101@redhat.com> <1291388987.7992.27.camel@marge.simson.net> <4CF90E3D.7090103@redhat.com> <20101203162003.GA13515@linux.vnet.ibm.com> <4CF9242D.4090007@redhat.com> Reply-To: vatsa@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mike Galbraith , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Avi Kiviti , Peter Zijlstra , Ingo Molnar , Anthony Liguori To: Rik van Riel Return-path: Received: from e37.co.us.ibm.com ([32.97.110.158]:54519 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752920Ab0LCRaB (ORCPT ); Fri, 3 Dec 2010 12:30:01 -0500 Content-Disposition: inline In-Reply-To: <4CF9242D.4090007@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Fri, Dec 03, 2010 at 12:09:01PM -0500, Rik van Riel wrote: > I don't see how that is going to help get the lock > released, when the VCPU holding the lock is on another > CPU. Even the directed yield() is not guaranteed to get the lock released, given its shooting in the dark? Anyway, the intention of yield() proposed was not to get lock released immediately (which will happen eventually), but rather to avoid inefficiency associated with (long) spinning and at the same time make sure we are not leaking our bandwidth to other guests because of a naive yield .. - vatsa