Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756225AbYKVKJu (ORCPT ); Sat, 22 Nov 2008 05:09:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752893AbYKVKJk (ORCPT ); Sat, 22 Nov 2008 05:09:40 -0500 Received: from viefep18-int.chello.at ([213.46.255.22]:25149 "EHLO viefep18-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752738AbYKVKJj (ORCPT ); Sat, 22 Nov 2008 05:09:39 -0500 X-SourceIP: 213.46.9.244 Subject: Re: [patch] sched: add locking when update the task_group's cfs_rq[] array. From: Peter Zijlstra To: Chris Friesen Cc: Ken Chen , Ingo Molnar , Linux Kernel Mailing List , Dhaval Giani In-Reply-To: <49248A35.4080401@nortel.com> References: <1227113662.29743.46.camel@lappy.programming.kicks-ass.net> <1227128331.29743.61.camel@lappy.programming.kicks-ass.net> <49248A35.4080401@nortel.com> Content-Type: text/plain Date: Sat, 22 Nov 2008 11:09:35 +0100 Message-Id: <1227348575.7685.19024.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1159 Lines: 26 On Wed, 2008-11-19 at 15:50 -0600, Chris Friesen wrote: > Peter Zijlstra wrote: > > > Will it scale, half-way, I'd say. It races a little, but should > > converge. The biggest issue is that we're running with 10 bit fixed > > point math, and on large cpu machines you get into granularity problems. > > Is there any way to get higher resolution math on 64-bit machines? (I'm > assuming that most larger SMP boxes will be 64-bit capable.) Yes, if we do the same thing we do for 64bit math on 32bit boxen to obtain 128bit math on 64bit boxen. Trouble seems to be gcc, which imho f*'ed up by not providing a long long long (or whatever), there does seem to be something but all the gcc people tell me its fragile and not to be used. Anyway, I've been meaning to send a RFC to linux-arch about adding something like this, which we'd then have to do our-selves with C functions instead of nice integer types :/ -- 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/