From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751993AbcGFGxW (ORCPT ); Wed, 6 Jul 2016 02:53:22 -0400 Received: from merlin.infradead.org ([205.233.59.134]:34061 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750780AbcGFGxR (ORCPT ); Wed, 6 Jul 2016 02:53:17 -0400 Date: Wed, 6 Jul 2016 08:52:55 +0200 From: Peter Zijlstra To: Pan Xinhui Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, linux-s390@vger.kernel.org, mingo@redhat.com, mpe@ellerman.id.au, paulus@samba.org, benh@kernel.crashing.org, paulmck@linux.vnet.ibm.com, waiman.long@hpe.com, will.deacon@arm.com, boqun.feng@gmail.com, dave@stgolabs.net, schwidefsky@de.ibm.com, pbonzini@redhat.com Subject: Re: [PATCH v2 0/4] implement vcpu preempted check Message-ID: <20160706065255.GH30909@twins.programming.kicks-ass.net> References: <1467124991-13164-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1467124991-13164-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 28, 2016 at 10:43:07AM -0400, Pan Xinhui wrote: > change fomr v1: > a simplier definition of default vcpu_is_preempted > skip mahcine type check on ppc, and add config. remove dedicated macro. > add one patch to drop overload of rwsem_spin_on_owner and mutex_spin_on_owner. > add more comments > thanks boqun and Peter's suggestion. > > This patch set aims to fix lock holder preemption issues. > > test-case: > perf record -a perf bench sched messaging -g 400 -p && perf report > > 18.09% sched-messaging [kernel.vmlinux] [k] osq_lock > 12.28% sched-messaging [kernel.vmlinux] [k] rwsem_spin_on_owner > 5.27% sched-messaging [kernel.vmlinux] [k] mutex_unlock > 3.89% sched-messaging [kernel.vmlinux] [k] wait_consider_task > 3.64% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq > 3.41% sched-messaging [kernel.vmlinux] [k] mutex_spin_on_owner.is > 2.49% sched-messaging [kernel.vmlinux] [k] system_call > > We introduce interface bool vcpu_is_preempted(int cpu) and use it in some spin > loops of osq_lock, rwsem_spin_on_owner and mutex_spin_on_owner. > These spin_on_onwer variant also cause rcu stall before we apply this patch set > Paolo, could you help out with an (x86) KVM interface for this? Waiman, could you see if you can utilize this to get rid of the SPIN_THRESHOLD in qspinlock_paravirt?