From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422661AbcFHIMd (ORCPT ); Wed, 8 Jun 2016 04:12:33 -0400 Received: from mail-oi0-f43.google.com ([209.85.218.43]:35164 "EHLO mail-oi0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161701AbcFHIM0 (ORCPT ); Wed, 8 Jun 2016 04:12:26 -0400 MIME-Version: 1.0 In-Reply-To: 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 16:12:25 +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 16:04 GMT+08:00 Wanpeng Li : > 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 s/dynamic/dynticks > 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. s/dynamic/dynticks > > Regards, > Wanpeng Li -- Regards, Wanpeng Li