From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754879Ab1I1Pen (ORCPT ); Wed, 28 Sep 2011 11:34:43 -0400 Received: from merlin.infradead.org ([205.233.59.134]:45760 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753168Ab1I1Pem convert rfc822-to-8bit (ORCPT ); Wed, 28 Sep 2011 11:34:42 -0400 Subject: Re: [RFD 4/9] Make total_forks per-cgroup From: Peter Zijlstra To: Glauber Costa Cc: Martin Schwidefsky , linux-kernel@vger.kernel.org, paul@paulmenage.org, lizf@cn.fujitsu.com, daniel.lezcano@free.fr, jbottomley@parallels.com, Heiko Carstens Date: Wed, 28 Sep 2011 17:33:58 +0200 In-Reply-To: <4E833D6D.1030407@parallels.com> References: <1316816432-9237-1-git-send-email-glommer@parallels.com> <1316816432-9237-5-git-send-email-glommer@parallels.com> <1317160837.21836.21.camel@twins> <20110928101357.5a90c2ab@de.ibm.com> <1317206124.20318.6.camel@twins> <20110928144218.6a4882e5@de.ibm.com> <1317214418.24040.13.camel@twins> <4E833D6D.1030407@parallels.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.0.3- Message-ID: <1317224038.24040.52.camel@twins> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2011-09-28 at 12:29 -0300, Glauber Costa wrote: > On 09/28/2011 09:53 AM, Peter Zijlstra wrote: > > On Wed, 2011-09-28 at 14:42 +0200, Martin Schwidefsky wrote: > > > >>> That is, am I missing some added value of all this cputime*() foo? > >> > >> C can do the math as long as the encoding of the cputime is simple enough. > >> Can we demand that a cputime value needs to be an integral type ? > > > > I'd like to think we can ;-) > > > >> What I did when I wrote all that stuff is to define cputime_t as a struct > >> that contains a single u64. That way I found all the places in the kernel > >> that used a cputime and could convert the code accordingly. > > > > Indeed, that makes it a non-simple type and breaks all the C arith bits. > > > >> My fear is that if the cputime_xxx operations are removed, code will > >> sneak in again that just uses an unsigned long instead of a cputime_t. > >> That would break any arch that requires something bigger than a u32 for > >> its cputime. > > > > Which is only a problem for 32bit archs, of which s390 is the only one > > that matters, right? Hurm,. could we do something with sparse? Lots of > > people run sparse. > > > Well, I think x86-32 is unlikely to ever really go away. Sadly I'd agree with you, but that's not really the point, the only 32 bit arch that has !32 bit cputime_t is s390. But yeah, death to ia32 (and everything else 32bit fwiw)!