linux-kernel - [PATCH tip/core/rcu 2/3] kthread: Add pointer to vmstat-avoidance patch

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Date:	Tue, 24 Sep 2013 18:17:22 -0700
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,
	sbw@....edu, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 2/3] kthread: Add pointer to vmstat-avoidance patch

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 Documentation/kernel-per-CPU-kthreads.txt | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt
index 32351bf..827104f 100644
--- a/Documentation/kernel-per-CPU-kthreads.txt
+++ b/Documentation/kernel-per-CPU-kthreads.txt
@@ -181,12 +181,17 @@ To reduce its OS jitter, do any of the following:
 		make sure that this is safe on your particular system.
 	d.	It is not possible to entirely get rid of OS jitter
 		from vmstat_update() on CONFIG_SMP=y systems, but you
-		can decrease its frequency by writing a large value to
-		/proc/sys/vm/stat_interval.  The default value is HZ,
-		for an interval of one second.  Of course, larger values
-		will make your virtual-memory statistics update more
-		slowly.  Of course, you can also run your workload at
-		a real-time priority, thus preempting vmstat_update().
+		can decrease its frequency by writing a large value
+		to /proc/sys/vm/stat_interval.	The default value is
+		HZ, for an interval of one second.  Of course, larger
+		values will make your virtual-memory statistics update
+		more slowly.  Of course, you can also run your workload
+		at a real-time priority, thus preempting vmstat_update(),
+		but if your workload is CPU-bound, this is a bad idea.
+		However, there is an RFC patch from Christoph Lameter
+		(based on an earlier one from Gilad Ben-Yossef) that
+		reduces or even eliminates vmstat overhead for some
+		workloads at https://lkml.org/lkml/2013/9/4/379.
 	e.	If running on high-end powerpc servers, build with
 		CONFIG_PPC_RTAS_DAEMON=n.  This prevents the RTAS
 		daemon from running on each CPU every second or so.
-- 
1.8.1.5

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