From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751546AbcGLEQK (ORCPT ); Tue, 12 Jul 2016 00:16:10 -0400 Received: from mx2.suse.de ([195.135.220.15]:40877 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750763AbcGLEQI (ORCPT ); Tue, 12 Jul 2016 00:16:08 -0400 Subject: Re: [PATCH v2 0/4] implement vcpu preempted check To: Waiman Long , Peter Zijlstra References: <1467124991-13164-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> <20160706065255.GH30909@twins.programming.kicks-ass.net> <5783B6D7.7020903@hpe.com> Cc: linux-s390@vger.kernel.org, dave@stgolabs.net, benh@kernel.crashing.org, Pan Xinhui , boqun.feng@gmail.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, mingo@redhat.com, paulus@samba.org, mpe@ellerman.id.au, schwidefsky@de.ibm.com, pbonzini@redhat.com, paulmck@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org From: Juergen Gross Message-ID: <57846F02.7000306@suse.com> Date: Tue, 12 Jul 2016 06:16:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: <5783B6D7.7020903@hpe.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/07/16 17:10, Waiman Long wrote: > On 07/06/2016 02:52 AM, Peter Zijlstra wrote: >> 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? > > That API is certainly useful to make the paravirt spinlock perform > better. However, I am not sure if we can completely get rid of the > SPIN_THRESHOLD at this point. It is not just the kvm, the xen code need > to be modified as well. This should be rather easy. The relevant information is included in the runstate data mapped into kernel memory. I can provide a patch for Xen if needed. Juergen