From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754161Ab1I1MyW (ORCPT ); Wed, 28 Sep 2011 08:54:22 -0400 Received: from casper.infradead.org ([85.118.1.10]:46125 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752279Ab1I1MyV convert rfc822-to-8bit (ORCPT ); Wed, 28 Sep 2011 08:54:21 -0400 Subject: Re: [RFD 4/9] Make total_forks per-cgroup From: Peter Zijlstra To: Martin Schwidefsky Cc: Glauber Costa , 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 14:53:38 +0200 In-Reply-To: <20110928144218.6a4882e5@de.ibm.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> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.0.3- Message-ID: <1317214418.24040.13.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 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.