Re: [PATCH v2] sched/cputime: steal_account_process_tick() should return jiffies

From	Frederic Weisbecker <fweisbec@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] sched/cputime: steal_account_process_tick() should return jiffies
Date	2016-03-08 13:40 +0100
Message-ID	<rap5F-Qj-35@gated-at.bofh.it> (permalink)
References	<r9717-5Id-11@gated-at.bofh.it> <r9hDc-4Hl-1@gated-at.bofh.it> <r9khH-6FU-5@gated-at.bofh.it> <r9ykG-8bj-1@gated-at.bofh.it> <r9zgJ-w6-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Sat, Mar 05, 2016 at 11:18:48PM -0600, Chris Friesen wrote:
> 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 <chris.friesen@windriver.com>

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

Thanks Chris!

Thread

[PATCH] steal_account_process_tick() should return jiffies Chris Friesen <cbf123@mail.usask.ca> - 2016-03-05 00:10 +0100
  Re: [PATCH] steal_account_process_tick() should return jiffies Thomas Gleixner <tglx@linutronix.de> - 2016-03-05 11:30 +0100
    Re: [PATCH] steal_account_process_tick() should return jiffies Frederic Weisbecker <fweisbec@gmail.com> - 2016-03-05 14:20 +0100
      Re: [PATCH] steal_account_process_tick() should return jiffies Chris Friesen <cbf123@mail.usask.ca> - 2016-03-06 05:20 +0100
        [PATCH v2] sched/cputime: steal_account_process_tick() should return  jiffies Chris Friesen <cbf123@mail.usask.ca> - 2016-03-06 06:20 +0100
          Re: [PATCH v2] sched/cputime: steal_account_process_tick() should  return jiffies Thomas Gleixner <tglx@linutronix.de> - 2016-03-06 12:10 +0100
          Re: [PATCH v2] sched/cputime: steal_account_process_tick() should  return jiffies Frederic Weisbecker <fweisbec@gmail.com> - 2016-03-08 13:40 +0100
          [tip:sched/core] sched/cputime: Fix steal_account_process_tick() to  always return jiffies tip-bot for Chris Friesen <tipbot@zytor.com> - 2016-03-08 14:20 +0100

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