From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Kevin Hilman <khilman@linaro.org>, Tejun Heo <tj@kernel.org>,
Lai Jiangshan <laijs@cn.fujitsu.com>,
Zoran Markovic <zoran.markovic@linaro.org>,
linux-kernel@vger.kernel.org,
Shaibal Dutta <shaibal.dutta@broadcom.com>,
Dipankar Sarma <dipankar@in.ibm.com>
Subject: Re: [RFC PATCH] rcu: move SRCU grace period work to power efficient workqueue
Date: Wed, 12 Feb 2014 11:02:41 -0800 [thread overview]
Message-ID: <20140212190241.GD4250@linux.vnet.ibm.com> (raw)
In-Reply-To: <20140212182336.GD5496@localhost.localdomain>
On Wed, Feb 12, 2014 at 07:23:38PM +0100, Frederic Weisbecker wrote:
> On Mon, Feb 10, 2014 at 10:47:29AM -0800, Paul E. McKenney wrote:
> > On Mon, Feb 10, 2014 at 06:08:31PM +0800, Lai Jiangshan wrote:
> > > Acked-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> >
> > Thank you all, queued for 3.15.
> >
> > We should also have some facility for moving the SRCU workqueues to
> > housekeeping/timekeeping kthreads in the NO_HZ_FULL case. Or does
> > this patch already have that effect?
>
> Kevin Hilman and me plan to try to bring a new Kconfig option that could let
> us control the unbound workqueues affinity through sysfs.
Please CC me or feel free to update Documentation/kernel-per-CPU-kthreads.txt
as part of this upcoming series.
> The feature actually exist currently but is only enabled for workqueues that
> have WQ_SYSFS. Writeback and raid5 are the only current users.
>
> See for example: /sys/devices/virtual/workqueue/writeback/cpumask
Ah, news to me! I have queued the following patch, seem reasonable?
Thanx, Paul
------------------------------------------------------------------------
diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt
index 827104fb9364..09f28841ee3e 100644
--- a/Documentation/kernel-per-CPU-kthreads.txt
+++ b/Documentation/kernel-per-CPU-kthreads.txt
@@ -162,7 +162,11 @@ Purpose: Execute workqueue requests
To reduce its OS jitter, do any of the following:
1. Run your workload at a real-time priority, which will allow
preempting the kworker daemons.
-2. Do any of the following needed to avoid jitter that your
+2. Use the /sys/devices/virtual/workqueue/*/cpumask sysfs files
+ to force the WQ_SYSFS workqueues to run on the specified set
+ of CPUs. The set of WQ_SYSFS workqueues can be displayed using
+ "ls sys/devices/virtual/workqueue".
+3. Do any of the following needed to avoid jitter that your
application cannot tolerate:
a. Build your kernel with CONFIG_SLUB=y rather than
CONFIG_SLAB=y, thus avoiding the slab allocator's periodic
next prev parent reply other threads:[~2014-02-12 19:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-31 19:53 [RFC PATCH] rcu: move SRCU grace period work to power efficient workqueue Zoran Markovic
2014-01-31 20:10 ` Zoran Markovic
2014-02-10 10:08 ` Lai Jiangshan
2014-02-10 18:47 ` Paul E. McKenney
2014-02-12 18:23 ` Frederic Weisbecker
2014-02-12 19:02 ` Paul E. McKenney [this message]
2014-02-12 19:23 ` Tejun Heo
2014-02-12 19:59 ` Paul E. McKenney
2014-02-12 20:13 ` Tejun Heo
2014-02-12 23:04 ` Frederic Weisbecker
2014-02-13 0:33 ` Paul E. McKenney
2014-02-13 1:30 ` Lai Jiangshan
2014-02-13 14:05 ` Frederic Weisbecker
2014-02-14 23:24 ` Kevin Hilman
2014-02-15 7:36 ` Mike Galbraith
2014-02-16 16:41 ` Paul E. McKenney
2014-02-17 4:50 ` Mike Galbraith
2014-02-19 7:00 ` Mike Galbraith
2014-02-24 17:55 ` Kevin Hilman
2014-02-24 18:25 ` Mike Galbraith
2014-02-27 15:08 ` Frederic Weisbecker
2014-03-10 9:52 ` Viresh Kumar
2014-02-17 5:26 ` Mike Galbraith
2014-02-27 14:43 ` Frederic Weisbecker
2014-02-27 15:22 ` Mike Galbraith
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