From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932273AbcHKFth (ORCPT ); Thu, 11 Aug 2016 01:49:37 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:33362 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751562AbcHKFtf (ORCPT ); Thu, 11 Aug 2016 01:49:35 -0400 From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org Cc: Wanpeng Li , Ingo Molnar , "Peter Zijlstra (Intel)" , Rik van Riel , Thomas Gleixner , Frederic Weisbecker , Paolo Bonzini , Radim Subject: [PATCH] sched/cputime: Fix fold steal time into idle time accounting Date: Thu, 11 Aug 2016 13:36:35 +0800 Message-Id: <1470893795-3527-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li Commit: 57430218317 ("sched/cputime: Count actually elapsed irq & softirq time") ... didn't take steal time into consideration with passing the noirqtime kernel parameter. As Paolo pointed out before: | Why not? If idle=poll, for example, any time the guest is suspended (and | thus cannot poll) does count as stolen time. This patch fixes it by reducing steal time from idle time accounting when the noirqtime is true. The average idle time drops from 56.8% to 54.75% for nohz idle kvm guest(noirqtime, idle=poll, four vCPUs running on one pCPU). Cc: Ingo Molnar Cc: Peter Zijlstra (Intel) Cc: Rik van Riel Cc: Thomas Gleixner Cc: Frederic Weisbecker Cc: Paolo Bonzini Cc: Radim Signed-off-by: Wanpeng Li --- kernel/sched/cputime.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 1934f65..8b9bcc5 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -508,13 +508,20 @@ void account_process_tick(struct task_struct *p, int user_tick) */ void account_idle_ticks(unsigned long ticks) { - + cputime_t cputime, steal; if (sched_clock_irqtime) { irqtime_account_idle_ticks(ticks); return; } - account_idle_time(jiffies_to_cputime(ticks)); + cputime = cputime_one_jiffy; + steal = steal_account_process_time(cputime); + + if (steal >= cputime) + return; + + cputime -= steal; + account_idle_time(cputime); } /* -- 1.9.1