From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754848AbcJELBM (ORCPT ); Wed, 5 Oct 2016 07:01:12 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:35725 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751803AbcJELBK (ORCPT ); Wed, 5 Oct 2016 07:01:10 -0400 Subject: Re: [PATCH v3 0/4] implement vcpu preempted check To: Pan Xinhui , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, linux-s390@vger.kernel.org, xen-devel-request@lists.xenproject.org, kvm@vger.kernel.org References: <1469101514-49475-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, mingo@redhat.com, peterz@infradead.org, paulmck@linux.vnet.ibm.com, will.deacon@arm.com, kernellwp@gmail.com, jgross@suse.com, pbonzini@redhat.com, bsingharora@gmail.com From: Christian Borntraeger Date: Wed, 5 Oct 2016 13:00:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <1469101514-49475-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16100511-0032-0000-0000-00000221FBD5 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16100511-0033-0000-0000-00001D281EC5 Message-Id: <847f7377-61d3-835e-458b-aa9f4f5fcf8c@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-10-05_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1610050189 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/21/2016 01:45 PM, Pan Xinhui wrote: > change from v2: > no code change, fix typos, update some comments > > change from 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 > > before patch: > 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 > > after patch: > 9.99% sched-messaging [kernel.vmlinux] [k] mutex_unlock > 5.28% sched-messaging [unknown] [H] 0xc0000000000768e0 > 4.27% sched-messaging [kernel.vmlinux] [k] __copy_tofrom_user_power7 > 3.77% sched-messaging [kernel.vmlinux] [k] copypage_power7 > 3.24% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq > 3.02% sched-messaging [kernel.vmlinux] [k] system_call > 2.69% sched-messaging [kernel.vmlinux] [k] wait_consider_task > > 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 > > Pan Xinhui (4): > kernel/sched: introduce vcpu preempted check interface > powerpc/spinlock: support vcpu preempted check > locking/osq: Drop the overhead of osq_lock() > kernel/locking: Drop the overhead of {mutex,rwsem}_spin_on_owner > > arch/powerpc/include/asm/spinlock.h | 18 ++++++++++++++++++ > include/linux/sched.h | 12 ++++++++++++ > kernel/locking/mutex.c | 15 +++++++++++++-- > kernel/locking/osq_lock.c | 10 +++++++++- > kernel/locking/rwsem-xadd.c | 16 +++++++++++++--- > 5 files changed, 65 insertions(+), 6 deletions(-) > Acked-by: Christian Borntraeger for the full series. With my patch on top this really improves some benchmarks for overcommitted KVM guests.