Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932293AbWEHEqS (ORCPT ); Mon, 8 May 2006 00:46:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932297AbWEHEqS (ORCPT ); Mon, 8 May 2006 00:46:18 -0400 Received: from smtp105.mail.mud.yahoo.com ([209.191.85.215]:58985 "HELO smtp105.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S932293AbWEHEqR (ORCPT ); Mon, 8 May 2006 00:46:17 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=1D4YzW5moG2SPWL7D8WHWEN+27csVu42aVwVTNfaZ8xiXNKNUcJL3iYFH4R0AzyFEJaCoI1r7GIjs+Z48E5X0eFk2T+FhqUCQBsYRe3iZJ87GDoG3WGEDpyzvlRGH7kSETCGl/KSz4/Y5DeUo2hYmRx3tn8J7Es9mo4/wLjM4dU= ; Message-ID: <445ECD10.1090506@yahoo.com.au> Date: Mon, 08 May 2006 14:46:08 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050927 Debian/1.7.8-1sarge3 X-Accept-Language: en MIME-Version: 1.0 To: Mike Galbraith CC: Andi Kleen , Christopher Friesen , Russell King , linux-kernel@vger.kernel.org Subject: Re: sched_clock() uses are broken References: <20060502132953.GA30146@flint.arm.linux.org.uk> <44578EB9.8050402@nortel.com> <200605021859.18948.ak@suse.de> <445791D3.9060306@yahoo.com.au> <1146640155.7526.27.camel@homer> <445DE925.9010006@yahoo.com.au> <1147023122.13315.16.camel@homer> <1147061696.8544.12.camel@homer> <1147063063.8809.7.camel@homer> In-Reply-To: <1147063063.8809.7.camel@homer> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1340 Lines: 31 Mike Galbraith wrote: >Sorry for yet another reply, but running the old starvation testcase >that caused sched_clock() to be born in the first place tickled my >funny-bone. With that running and hitting 300k context switches... > >now: 2100508962835 tick: 2100508972067 stamp: 2100508961220 total: 2906 >now: 2101531243883 tick: 2101531251877 stamp: 2101531238543 total: 2924 >now: 2102695422392 tick: 2102695431699 stamp: 2102695418265 total: 2940 > >Accounting? Not :) > Yeah I agree with Andi that this accounting stuff is probably done for some POSIX conformance that doesn't matter. Actually it is worse than that because if anyone _really_ did need it, then they'll get a horrible surprise when their system mysteriously fails in production. It should either get ripped out, or perhaps converted to use jiffies until a sane high resolution, low overhead scheme is developed (if ever). And that would exclude something that does this accounting in fastpaths for the 99.99% of processes that never use it. -- Send instant messages to your online friends http://au.messenger.yahoo.com - 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/