Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754117AbcCHNS7 (ORCPT ); Tue, 8 Mar 2016 08:18:59 -0500 Received: from torg.zytor.com ([198.137.202.12]:52108 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751359AbcCHNSp (ORCPT ); Tue, 8 Mar 2016 08:18:45 -0500 Date: Tue, 8 Mar 2016 05:18:07 -0800 From: tip-bot for Chris Friesen Message-ID: Cc: cbf123@mail.usask.ca, mingo@kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org, torvalds@linux-foundation.org, tglx@linutronix.de, chris.friesen@windriver.com, hpa@zytor.com, fweisbec@gmail.com Reply-To: linux-kernel@vger.kernel.org, cbf123@mail.usask.ca, stable@vger.kernel.org, mingo@kernel.org, tglx@linutronix.de, fweisbec@gmail.com, chris.friesen@windriver.com, hpa@zytor.com, torvalds@linux-foundation.org, peterz@infradead.org In-Reply-To: <56DBBDB8.40305@mail.usask.ca> References: <56DBBDB8.40305@mail.usask.ca> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/cputime: Fix steal_account_process_tick() to always return jiffies Git-Commit-ID: f9c904b7613b8b4c85b10cd6b33ad41b2843fa9d X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2821 Lines: 73 Commit-ID: f9c904b7613b8b4c85b10cd6b33ad41b2843fa9d Gitweb: http://git.kernel.org/tip/f9c904b7613b8b4c85b10cd6b33ad41b2843fa9d Author: Chris Friesen AuthorDate: Sat, 5 Mar 2016 23:18:48 -0600 Committer: Ingo Molnar CommitDate: Tue, 8 Mar 2016 12:24:56 +0100 sched/cputime: Fix steal_account_process_tick() to always return jiffies The callers of steal_account_process_tick() expect it to return whether a jiffy should be considered stolen or not. Currently the return value of steal_account_process_tick() is in units of cputime, which vary between either jiffies or nsecs depending on CONFIG_VIRT_CPU_ACCOUNTING_GEN. If cputime has nsecs granularity and there is a tiny amount of stolen time (a few nsecs, say) then we will consider the entire tick stolen and will not account the tick on user/system/idle, causing /proc/stats to show invalid data. The fix is to change steal_account_process_tick() to accumulate the stolen time and only account it once it's worth a jiffy. (Thanks to Frederic Weisbecker for suggestions to fix a bug in my first version of the patch.) Signed-off-by: Chris Friesen Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Cc: Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/56DBBDB8.40305@mail.usask.ca Signed-off-by: Ingo Molnar --- kernel/sched/cputime.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 01d9898..75f98c5 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -262,21 +262,21 @@ static __always_inline bool steal_account_process_tick(void) #ifdef CONFIG_PARAVIRT if (static_key_false(¶virt_steal_enabled)) { u64 steal; - cputime_t steal_ct; + unsigned long steal_jiffies; steal = paravirt_steal_clock(smp_processor_id()); steal -= this_rq()->prev_steal_time; /* - * cputime_t may be less precise than nsecs (eg: if it's - * based on jiffies). Lets cast the result to cputime + * steal is in nsecs but our caller is expecting steal + * time in jiffies. Lets cast the result to jiffies * granularity and account the rest on the next rounds. */ - steal_ct = nsecs_to_cputime(steal); - this_rq()->prev_steal_time += cputime_to_nsecs(steal_ct); + steal_jiffies = nsecs_to_jiffies(steal); + this_rq()->prev_steal_time += jiffies_to_nsecs(steal_jiffies); - account_steal_time(steal_ct); - return steal_ct; + account_steal_time(jiffies_to_cputime(steal_jiffies)); + return steal_jiffies; } #endif return false;