linux-kernel - [PATCH tip/core/rcu 0/3] Crude timer-wheel latency hacks

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Message-ID: <20140114041449.GA13934@linux.vnet.ibm.com>
Date:	Mon, 13 Jan 2014 20:14:50 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com,
	edumazet@...gle.com, darren@...art.com, fweisbec@...il.com,
	oleg@...hat.com, sbw@....edu
Subject: [PATCH tip/core/rcu 0/3] Crude timer-wheel latency hacks

Hello!

The following three patches provide some crude timer-wheel latency
patches.  I understand that a more comprehensive solution is in progress,
but in the meantime, these patches work well in cases where a given
CPU has either zero or one timers pending, which is a common case for
NO_HZ_FULL kernels.  So, on the off-chance that this is helpful to
someone, the individual patches are as follows:

1.	Avoid jiffy-at-a-time stepping when the timer wheel is empty.

2.	Avoid jiffy-at-a-time stepping when the timer wheel transitions
	to empty.

3.	Avoid jiffy-at-a-time stepping after a timer is added to an
	initially empty timer wheel.

							Thanx, Paul

------------------------------------------------------------------------

 b/kernel/timer.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

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