Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932297Ab3CGPz3 (ORCPT ); Thu, 7 Mar 2013 10:55:29 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:45256 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752582Ab3CGPz1 (ORCPT ); Thu, 7 Mar 2013 10:55:27 -0500 Message-ID: <5138B84F.1060807@oracle.com> Date: Thu, 07 Mar 2013 09:54:55 -0600 From: Dave Kleikamp User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130221 Thunderbird/17.0.3 MIME-Version: 1.0 To: Chris Mason , Peter Zijlstra , Rik van Riel , Linus Torvalds , Waiman Long , Davidlohr Bueso , Emmanuel Benisty , "Vinod, Chegu" , "Low, Jason" , "H. Peter Anvin" , Andrew Morton , "aquini@redhat.com" , Michel Lespinasse , Ingo Molnar , Larry Woodman , Linux Kernel Mailing List , Steven Rostedt , Thomas Gleixner , Chris Mason Subject: Re: [PATCH v2 0/4] ipc: reduce ipc lock contention References: <1362476149.2225.50.camel@buesod1.americas.hpqcorp.net> <513626E9.2040509@redhat.com> <51364AB9.80206@hp.com> <51365B66.5010905@redhat.com> <1362645933.2606.14.camel@laptop> <20130307125546.GD13323@shiny.masoncoding.com> In-Reply-To: <20130307125546.GD13323@shiny.masoncoding.com> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2312 Lines: 57 On 03/07/2013 06:55 AM, Chris Mason wrote: > On Thu, Mar 07, 2013 at 01:45:33AM -0700, Peter Zijlstra wrote: >> On Tue, 2013-03-05 at 15:53 -0500, Rik van Riel wrote: >> >>> Indeed. Though how well my patches will work with Oracle will >>> depend a lot on what kind of semctl syscalls they are doing. >>> >>> Does Oracle typically do one semop per semctl syscall, or does >>> it pass in a whole bunch at once? >> >> https://oss.oracle.com/~mason/sembench.c >> >> I think Chris wrote that to match a particular pattern of semaphore >> operations the database engine in question does. I haven't checked to >> see if it triggers the case in point though. >> >> Also, Chris since left Oracle but maybe he knows who to poke. >> > > Dave Kleikamp (cc'd) took over my patches and did the most recent > benchmarking. Ported against 3.0: > > https://oss.oracle.com/git/?p=linux-uek-2.6.39.git;a=commit;h=c7fa322dd72b08450a440ef800124705a1fa148c > > The current versions are still in the 2.6.32 oracle kernel, but it looks > like they reverted this 3.0 commit. I think with Manfred's upstream > work my more complex approach wasn't required anymore, but hopefully > Dave can fill in details. >From what I recall, I could never get better performance from your patches that we saw with Manfred's work alone. I can't remember the reasons for including and then reverting the patches from the 3.0 (2.6.39) Oracle kernel, but in the end we weren't able to justify their inclusion. > Here is some of the original discussion around the patch: > > https://lkml.org/lkml/2010/4/12/257 > > In terms of how oracle uses IPC, the part that shows up in profiles is > using semtimedop for bulk wakeups. They can configure things to use > either a bunch of small arrays or a huge single array (and anything in > between). > > There is one IPC semaphore per process and they use this to wait for > some event (like a log commit). When the event comes in, everyone > waiting is woken in bulk via a semtimedop call. > > So, single proc waking many waiters at once. > > -chris > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/