Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751959AbYKNKBe (ORCPT ); Fri, 14 Nov 2008 05:01:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751040AbYKNKBY (ORCPT ); Fri, 14 Nov 2008 05:01:24 -0500 Received: from mail4.iitk.ac.in ([203.197.196.4]:49097 "EHLO mail4.iitk.ac.in" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750877AbYKNKBX (ORCPT ); Fri, 14 Nov 2008 05:01:23 -0500 Date: Fri, 14 Nov 2008 16:08:06 +0000 From: Rahul Pydimukkala To: Andy Lutomirski Cc: kyle , linux-kernel@vger.kernel.org Subject: Re: apache threads not balanced over all CPU cores, schedular problem or apache? Message-ID: <20081114160758.GA4074@csews22.cse.iitk.ac.in> References: <009401c9454c$6e3a8610$b902a8c0@kyle> <491CF509.7010101@myrealbox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <491CF509.7010101@myrealbox.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1905 Lines: 48 On 22:48 Thu 13 Nov , Andy Lutomirski wrote: > kyle wrote: > >top - 12:44:42 up 8 days, 15:45, 7 users, load average: 2.07, 1.86, 2.02 > >Tasks: 251 total, 1 running, 249 sleeping, 0 stopped, 1 zombie > >Cpu0 : 0.5%us, 0.5%sy, 0.0%ni, 99.0%id, 0.0%wa, 0.0%hi, 0.0%si, > >0.0%st > >Cpu1 : 14.6%us, 4.4%sy, 0.0%ni, 62.6%id, 17.0%wa, 0.0%hi, 1.5%si, > >0.0%st > >Cpu2 : 4.3%us, 1.4%sy, 0.0%ni, 93.8%id, 0.0%wa, 0.5%hi, 0.0%si, > >0.0%st > >Cpu3 : 0.0%us, 0.0%sy, 0.0%ni, 98.0%id, 2.0%wa, 0.0%hi, 0.0%si, > >0.0%st > >Mem: 8117172k total, 8060936k used, 56236k free, 357488k buffers > >Swap: 208824k total, 8436k used, 200388k free, 5765168k cached > > Looks like you're mostly idle or waiting for I/O. From this > information, it looks like the kernel is probably doing the right thing: > keeping a lot of processes that share the same memory and run for very > short periods of time on the same cores to minimize cacheline bouncing. > > > > >All httpd are running on cpu1 and cpu2 only for several hours, after that, > >all httpd may run on cpu1 and cpu3, or cpu2 and cpu3, etc. again for > >several > >hours. > > > >Since the apache is in prefork mode, every httpd instance should be quite > >independant, I suppose the CPU schedular should balance the processes over > >the avaiable cores. However never seen httpd processes evenly distributed > >to > >3 cores, or 4 cores. > > Is there any reason to expect it to run faster if it were balanced evenly? Totally convincing. Thanks Andy for making this clear. I/O-bound processes reap no advantage from processor-level parallelism. - Rahul -- 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/