From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753509AbbAHHqH (ORCPT ); Thu, 8 Jan 2015 02:46:07 -0500 Received: from smtp2.provo.novell.com ([137.65.250.81]:47843 "EHLO smtp2.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752368AbbAHHqF (ORCPT ); Thu, 8 Jan 2015 02:46:05 -0500 Message-ID: <1420703154.12346.10.camel@stgolabs.net> Subject: Re: [LKP] [mm] c8c06efa8b5: -7.6% unixbench.score From: Davidlohr Bueso To: Huang Ying Cc: LKML , LKP ML Date: Wed, 07 Jan 2015 23:45:54 -0800 In-Reply-To: <1420684064.6201.86.camel@linux.intel.com> References: <1420684064.6201.86.camel@linux.intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.7 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2015-01-08 at 10:27 +0800, Huang Ying wrote: Cc'ing Peter. > FYI, we noticed the below changes on > > commit c8c06efa8b552608493b7066c234cfa82c47fcea ("mm: convert i_mmap_mutex to rwsem") Same exact everything, except for the lock type. No sharing going on. > testbox/testcase/testparams: lituya/unixbench/performance-execl > > 83cde9e8ba95d180 c8c06efa8b552608493b7066c2 > ---------------- -------------------------- > %stddev %change %stddev > \ | \ > 721721 ± 1% +303.6% 2913110 ± 3% unixbench.time.voluntary_context_switches > 11767 ± 0% -7.6% 10867 ± 1% unixbench.score And this workload appears to be from execl, right? Make sense with some of those numbers!! > 2.323e+08 ± 0% -7.2% 2.157e+08 ± 1% unixbench.time.minor_page_faults > 207 ± 0% -7.0% 192 ± 1% unixbench.time.user_time > 4923450 ± 0% -5.7% 4641672 ± 0% unixbench.time.involuntary_context_switches > 584 ± 0% -5.2% 554 ± 0% unixbench.time.percent_of_cpu_this_job_got > 948 ± 0% -4.9% 902 ± 0% unixbench.time.system_time > 0 ± 0% +Inf% 672942 ± 2% latency_stats.hits.call_rwsem_down_write_failed.vma_adjust.__split_vma.split_vma.mprotect_fixup.SyS_mprotect.system_call_fastpath What does this "hits" thing mean exactly? Since I assume both before and after runs have the same level of concurrency when pounding on mmap operations, I doubt it means that its the amount of calls into the slowpath... in addition the lock is obviously contended so we can forget about anything in the fastpath. So this is a call_rwsem_down_write_failed() vs __mutex_lock_common() issue. Thanks, Davidlohr