linux-kernel - [PATCH tip/core/rcu 2/5] rcu: Update RCU_FAST_NO

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Message-Id: <1351617563-28506-2-git-send-email-paulmck@linux.vnet.ibm.com>
Date:	Tue, 30 Oct 2012 10:19:20 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, edumazet@...gle.com, darren@...art.com,
	fweisbec@...il.com, sbw@....edu, patches@...aro.org,
	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 2/5] rcu: Update RCU_FAST_NO_HZ help text

From: "Paul E. McKenney" <paul.mckenney@...aro.org>

The RCU_FAST_NO_HZ help text included a warning about overhead on large
systems, but that issue has since been resolved.  The main remaining
issue with RCU_FAST_NO_HZ is increased real-time latency.  This commit
therefore updates the help text accordingly.

Signed-off-by: Paul E. McKenney <paul.mckenney@...aro.org>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 init/Kconfig |   15 +++++++--------
 1 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 6fdd6e3..b63e798 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -582,14 +582,13 @@ config RCU_FAST_NO_HZ
 	depends on NO_HZ && SMP
 	default n
 	help
-	  This option causes RCU to attempt to accelerate grace periods
-	  in order to allow CPUs to enter dynticks-idle state more
-	  quickly.  On the other hand, this option increases the overhead
-	  of the dynticks-idle checking, particularly on systems with
-	  large numbers of CPUs.
-
-	  Say Y if energy efficiency is critically important, particularly
-	  	if you have relatively few CPUs.
+	  This option causes RCU to attempt to accelerate grace periods in
+	  order to allow CPUs to enter dynticks-idle state more quickly.
+	  On the other hand, this option increases the overhead of the
+	  dynticks-idle checking, thus degrading scheduling latency.
+
+	  Say Y if energy efficiency is critically important, and you don't
+	  	care about real-time response.
 
 	  Say N if you are unsure.
 
-- 
1.7.8

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