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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
	josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
	peterz@infradead.org, rostedt@goodmis.org,
	Valdis.Kletnieks@vt.edu, dhowells@redhat.com,
	edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com,
	sbw@mit.edu, patches@linaro.org,
	"Paul E. McKenney" <paul.mckenney@linaro.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 2/5] rcu: Update RCU_FAST_NO_HZ help text
Date: Tue, 30 Oct 2012 10:19:20 -0700	[thread overview]
Message-ID: <1351617563-28506-2-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <1351617563-28506-1-git-send-email-paulmck@linux.vnet.ibm.com>

From: "Paul E. McKenney" <paul.mckenney@linaro.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@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.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


  reply	other threads:[~2012-10-30 17:36 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-30 17:19 [PATCH tip/core/rcu 0/5] Idle changes for 3.8 Paul E. McKenney
2012-10-30 17:19 ` [PATCH tip/core/rcu 1/5] rcu: Remove rcu_switch() Paul E. McKenney
2012-10-30 17:19   ` Paul E. McKenney [this message]
2012-10-30 17:19   ` [PATCH tip/core/rcu 3/5] rcu: Add a module parameter to force use of expedited RCU primitives Paul E. McKenney
2012-10-30 17:19   ` [PATCH tip/core/rcu 4/5] rcu: Fix precedence error in cpu_needs_another_gp() Paul E. McKenney
2012-10-30 17:19   ` [PATCH tip/core/rcu 5/5] rcu: Wordsmith help text for RCU_USER_QS kernel parameter Paul E. McKenney

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