From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932665AbcBITsf (ORCPT ); Tue, 9 Feb 2016 14:48:35 -0500 Received: from g1t6214.austin.hp.com ([15.73.96.122]:60277 "EHLO g1t6214.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753801AbcBITse (ORCPT ); Tue, 9 Feb 2016 14:48:34 -0500 From: Waiman Long To: Ingo Molnar Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Linus Torvalds , Ding Tianhong , Jason Low , Davidlohr Bueso , "Paul E. McKenney" , Thomas Gleixner , Will Deacon , Tim Chen , Waiman Long Subject: [PATCH 0/2] locking/mutex: Enable optimistic spinning of lock waiter Date: Tue, 9 Feb 2016 14:47:40 -0500 Message-Id: <1455047262-27731-1-git-send-email-Waiman.Long@hpe.com> X-Mailer: git-send-email 1.7.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patchset is a variant of PeterZ's "locking/mutex: Avoid spinner vs waiter starvation" patch. The major difference is that the waiter-spinner won't enter into the OSQ used by the spinners. Instead, it will spin directly on the lock in parallel with the queue head of the OSQ. So there will be a bit more cacheline contention on the lock cacheline, but that shouldn't cause noticeable impact on system performance. This patchset tries to address 2 issues with Peter's patch: 1) Ding Tianhong still find that hanging task could happen in some cases. 2) Jason Low found that there was performance regression for some AIM7 workloads. By making the waiter-spinner to spin directly on the mutex, it will increase the chance for the waiter-spinner to get the lock instead of waiting in the OSQ for its turn. My own test on a 4-socket E7-4820 v3 system showed a regression of about 4% in the high_systime workload with Peter's patch which this new patch effectively eliminates. Waiman Long (2): locking/mutex: Add waiter parameter to mutex_optimistic_spin() locking/mutex: Enable optimistic spinning of woken task in wait queue kernel/locking/mutex.c | 68 ++++++++++++++++++++++++++++++++++------------- 1 files changed, 49 insertions(+), 19 deletions(-)