From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752112AbWFWWH0 (ORCPT ); Fri, 23 Jun 2006 18:07:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752103AbWFWWHZ (ORCPT ); Fri, 23 Jun 2006 18:07:25 -0400 Received: from omx2-ext.sgi.com ([192.48.171.19]:54439 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S1752091AbWFWWHZ (ORCPT ); Fri, 23 Jun 2006 18:07:25 -0400 Message-ID: <449C6620.1020203@engr.sgi.com> Date: Fri, 23 Jun 2006 15:07:28 -0700 From: Jay Lan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.13) Gecko/20060411 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andrew Morton CC: Shailabh Nagar , balbir@in.ibm.com, csturtiv@sgi.com, linux-kernel@vger.kernel.org Subject: Re: [Patch][RFC] Disabling per-tgid stats on task exit in taskstats References: <44892610.6040001@watson.ibm.com> <20060609010057.e454a14f.akpm@osdl.org> <448952C2.1060708@in.ibm.com> <20060609042129.ae97018c.akpm@osdl.org> <4489EE7C.3080007@watson.ibm.com> <449999D1.7000403@engr.sgi.com> <44999A98.8030406@engr.sgi.com> <44999F5A.2080809@watson.ibm.com> <4499D7CD.1020303@engr.sgi.com> <449C2181.6000007@watson.ibm.com> <20060623141926.b28a5fc0.akpm@osdl.org> In-Reply-To: <20060623141926.b28a5fc0.akpm@osdl.org> X-Enigmail-Version: 0.90.1.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: >On Fri, 23 Jun 2006 13:14:41 -0400 >Shailabh Nagar wrote: > > >>The results show that differential between tgid on and off >>starts becoming significant once the exit rate crosses roughly 1000 >>threads/second. Below that exit rate, the difference is negligible. >>Above it, the difference starts climbing rapidly. >> >>So I guess the question is whether this rate of exit is representative >>enough of real life to warrant making any more changes to the existing >>patchset, beyond the locking changes in 2. above. >> >>>>From my limited experience, I think this is too high an exit rate >>to be worrying about overhead. >> >> > >1000/sec isn't terribly high. CGI servers, shell scripts. > >And kernel development ;) A `pushpatch 1500' here does 992 fork/exec/exit >per second. > > >> %ovhd of tgid on over off >> (higher is worse) >> >>Exit User Sys Elapsed >>Rate Time Time Time >> >>2283 25.76 649.41 -0.14 >>1193 -10.53 88.81 -0.12 >>963 -11.90 3.28 -0.10 >>806 -8.54 -0.84 0.16 >>694 -4.41 2.38 0.03 >> > >Oh wow. Something's gone quadratic there. > It was due to a loop in fill_tgid() when per-TG stats data are assembled for netlink: do { rc = delayacct_add_tsk(stats, tsk); if (rc) break; } while_each_thread(first, tsk); and it is executed inside a lock. Fortunately single threaded appls do not hit this code. - jay