linux-kernel - [GIT PULL timers] Timer-wheel bandaids^Wcommits for 3.15

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Message-ID: <20140228012704.GA20805@linux.vnet.ibm.com>
Date:	Thu, 27 Feb 2014 17:27:04 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	tglx@...utronix.de, mingo@...nel.org
Cc:	linux-kernel@...r.kernel.org, josh@...htriplett.org,
	peterz@...radead.org, oleg@...hat.com, rostedt@...dmis.org,
	bitbucket@...ine.de
Subject: [GIT PULL timers] Timer-wheel bandaids^Wcommits for 3.15

Hello, Thomas and Ingo,

This pull request contains latency bandaids^Woptimizations to the
timer-wheel code that are useful in conjunction with NO_HZ_FULL Kconfig
option.  These optimizations reduce the jiffy-by-jiffy looping in cases
where there is either zero or one timers in the timer wheel, which is
a common case for NO_HZ_FULL "worker" CPUs that run almost entirely
in usermode for a single task.

This is of course no substitute for a more extensive reworking of the
timer-wheel code, but it does provide some simple patches that can
provide significant latency improvements for NO_HZ_FULL systems that
have CPUs that very rarely enter the kernel.

							Thanx, Paul

These changes since commit 849401b66d305f3feb75b6db7459b95ad190552a:

  tick: Fixup more fallout from hrtimer broadcast mode (2014-02-09 15:11:47 +0100)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git timers.2014.02.25a

for you to fetch changes up to aea369b959bef10d235cd0714789cd8b0fe170b8:

  timers: Make internal_add_timer() update ->next_timer if ->active_timers == 0 (2014-02-25 12:39:01 -0800)

----------------------------------------------------------------
Oleg Nesterov (1):
      timers: Make internal_add_timer() update ->next_timer if ->active_timers == 0

Paul E. McKenney (4):
      timers: Track total number of timers in list
      timers: Reduce __run_timers() latency for empty list
      timers: Reduce future __run_timers() latency for newly emptied list
      timers: Reduce future __run_timers() latency for first add to empty list

 kernel/timer.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

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