From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752596AbcHMBod (ORCPT ); Fri, 12 Aug 2016 21:44:33 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:41575 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752248AbcHMBoc (ORCPT ); Fri, 12 Aug 2016 21:44:32 -0400 Subject: Re: [PATCH v2] locking/percpu-rwsem: Optimize readers and reduce global impact References: <20160809095112.GG30192@twins.programming.kicks-ass.net> <20160810075606.GK6879@twins.programming.kicks-ass.net> <20160810170946.GA11051@redhat.com> <5a2cc178ee03466fa3b104f8f28b44ff@NASANEXM02C.na.qualcomm.com> To: Peter Zijlstra Cc: John Stultz , "Paul E. McKenney" , Ingo Molnar , lkml , Tejun Heo , Dmitry Shmidt , Rom Lemarchand , Colin Cross , Todd Kjos From: Om Dhyade Message-ID: Date: Fri, 12 Aug 2016 18:44:28 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <5a2cc178ee03466fa3b104f8f28b44ff@NASANEXM02C.na.qualcomm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thank you Dimtry for sharing the patches. Update from my tests: Use-case: Android application launches. I tested the patches on android N build, i see max latency ~7ms. In my tests, the wait is due to: copy_process(fork.c) blocks all threads in __cgroup_procs_write including threads which are not part of the forking process's thread-group. Dimtry had provided a hack patch which reverts to per-process rw-sem which had max latency of ~2ms. android user-space binder library does 2 cgroup write operations per transaction, apart from the copy_process(fork.c) wait, i see pre-emption in _cgroup_procs_write causing waits. Thanks. -- The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project