linux-kernel - [RFC PATCH 0/5] nohz: Fix racy sleeptime stats v2

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Date:	Sat, 19 Oct 2013 17:17:16 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Fernando Luis Vazquez Cao <fernando_b1@....ntt.co.jp>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: [RFC PATCH 0/5] nohz: Fix racy sleeptime stats v2

Hi,

So this is a new iteration with some more changes on top of the latest discussions
we had.

Unfortunately it's not yet a real viable solution. Check out patch 4/5 for details,
I think that's too much overhead. Also it changes enough the semantics to break the
idle sleeptime accounting along the way. This is because moving the accounting to
io_schedule() makes it account _all_ IO sleeptime, even if the CPU is still busy,
not just when it is idle like before. As a result, the idle sleeptime, that relies on
a diff against the io sleeptime, is broken.

Anyway, my hope with this new take is mostly to launch a discussion with a fresher
base and see if we can find better ideas.

Thanks!

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	sched/iowait

Thanks,
	Frederic
---

Frederic Weisbecker (5):
      nohz: Convert a few places to use local per cpu accesses
      nohz: Only update sleeptime stats locally
      timer: Change idle/iowait accounting semantics
      sched: Refactor iowait accounting
      nohz: Synchronize sleep time stats with seqlock


 include/linux/ktime.h        |   7 +++
 include/linux/sched.h        |   1 +
 include/linux/tick.h         |  11 ++--
 kernel/sched/core.c          |  68 ++++++++++++++++++---
 kernel/sched/cputime.c       |   2 +-
 kernel/sched/sched.h         |   5 +-
 kernel/softirq.c             |   4 +-
 kernel/time/tick-broadcast.c |   6 +-
 kernel/time/tick-internal.h  |   4 +-
 kernel/time/tick-sched.c     | 138 ++++++++++++++-----------------------------
 kernel/time/timer_list.c     |   3 +-
 11 files changed, 130 insertions(+), 119 deletions(-)
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