From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754836Ab1I1P1i (ORCPT ); Wed, 28 Sep 2011 11:27:38 -0400 Received: from mx2.parallels.com ([64.131.90.16]:55239 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752938Ab1I1P1h (ORCPT ); Wed, 28 Sep 2011 11:27:37 -0400 Message-ID: <4E833CAF.7010208@parallels.com> Date: Wed, 28 Sep 2011 12:26:39 -0300 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0.2) Gecko/20110906 Thunderbird/6.0.2 MIME-Version: 1.0 To: Martin Schwidefsky CC: Peter Zijlstra , , , , , , Heiko Carstens Subject: Re: [RFD 4/9] Make total_forks per-cgroup 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> In-Reply-To: <20110928101357.5a90c2ab@de.ibm.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [187.46.219.221] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/28/2011 05:13 AM, Martin Schwidefsky wrote: > On Wed, 28 Sep 2011 00:00:37 +0200 > Peter Zijlstra wrote: > >> On Fri, 2011-09-23 at 19:20 -0300, Glauber Costa wrote: >>> @@ -1039,6 +1035,8 @@ static void posix_cpu_timers_init(struct task_struct *tsk) >>> INIT_LIST_HEAD(&tsk->cpu_timers[2]); >>> } >>> >>> +struct task_group *task_group(struct task_struct *p); >> >> That doesn't appear to be actually used in this file.. >> >> Also, since there's already a for_each_possible_cpu() loop in that >> proc/stat function, would it yield some code improvement to make >> total_forks a cpu_usage_stat? >> >> I guess the whole cputime64_t crap gets in the way of that being >> natural... >> >> We could of course kill off the cputime64_t thing, its pretty pointless >> and its a u64 all over the board. I think Martin or Heiko created this >> stuff (although I might be wrong, my git tree doesn't go back that far). > > The reason to introduce cputime_t has been that different architecture > needed differently sized integers for their respective representation > of cputime. On x86-32 the number of ticks is recorded in a u32, on s390 > we needed a u64 for the cpu timer values. cputime64_t is needed for > cpustat and other sums of cputime that would overflow a cputime_t > (in particular on x86-32 with the u32 cputime_t and the u64 cputime64_t). > > Now we would convert everything to u64 but that would cause x86-32 to > use 64-bit arithmetic for the tick counter. If that is acceptable I > can't say. > If we get rid of cputime64_t, it doesn't mean we need to get rid of cputime_t. Or am I missing the point here? We would still have to call an analogous of cputime_to_cputime64 before using it, but I get that where it matters, gcc can even make it void. And for all the rest, we do u64 math and typing and just get happy.