From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755989AbcFHIE4 (ORCPT ); Wed, 8 Jun 2016 04:04:56 -0400 Received: from mail-oi0-f50.google.com ([209.85.218.50]:33905 "EHLO mail-oi0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751399AbcFHIEw (ORCPT ); Wed, 8 Jun 2016 04:04:52 -0400 MIME-Version: 1.0 In-Reply-To: <20160608075210.GA8970@gmail.com> References: <1465355110-21714-1-git-send-email-wanpeng.li@hotmail.com> <1465355110-21714-3-git-send-email-wanpeng.li@hotmail.com> <20160608072257.GA9612@gmail.com> <20160608075210.GA8970@gmail.com> From: Wanpeng Li Date: Wed, 8 Jun 2016 16:04:51 +0800 Message-ID: Subject: Re: [PATCH v5 3/3] sched/cputime: Add steal time support to full dynticks CPU time accounting To: Ingo Molnar Cc: Rik van Riel , =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= , "linux-kernel@vger.kernel.org" , kvm , Wanpeng Li , "Peter Zijlstra (Intel)" , Thomas Gleixner , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2016-06-08 15:52 GMT+08:00 Ingo Molnar : > > * Wanpeng Li wrote: > >> 2016-06-08 15:22 GMT+08:00 Ingo Molnar : >> > >> > * Wanpeng Li wrote: >> > >> >> From: Wanpeng Li >> >> >> >> This patch adds guest steal-time support to full dynticks CPU >> >> time accounting. After the following commit: >> >> >> >> ff9a9b4c4334 ("sched, time: Switch VIRT_CPU_ACCOUNTING_GEN to jiffy granularity") >> >> >> >> ... time sampling became jiffy based, even if it's still listened >> >> to ring boundaries, so steal_account_process_tick() is reused >> >> to account how many 'ticks' are stolen-time, after the last accumulation. >> > >> > So the 'ring boundary' part still doesn't parse (neither grammatically nor >> > logically) - please rephrase it because I have no idea what you want to say here. >> >> It is original from this slides. >> http://ertl.jp/~shinpei/conf/ospert13/slides/FredericWeisbecker.pdf, >> slide 28. > > Yes, I now understand that this is meant as 'context tracking is active', but I > don't understand the way you use it in this changelog's context. > > Btw., the grammatically correct way to add that phrase would have been: > > ... time sampling became jiffy based, even if it's still listening to ring > boundaries, so steal_account_process_tick() is reused to account how many > 'ticks' are stolen-time, after the last accumulation. Thanks, Ingo! > > But I still don't understand it, nor did Paolo understand it. > > Nor is there any 0/3 boilerplace description that gives some context about what > these changes are about. Exactly what do you mean by 'add steal-time support' - we > clearly had that before. So is your patch lifting some limitation? Or was > steal-time accounting totally inactive with certain dynticks configurations? The > changelog does not tell us anything about that... Now I understand why you said "write-only code". vtime(depends on context tracking) which is just used in full dynamic doesn't account steal time, however, periodic/nohz idle which not use vtime have codes account steal time in cputime.c, this patch add the steal time acccount support in vtime which will be used in full dynamic guest. Regards, Wanpeng Li