* [PATCH] rcu: Advise most users not to enable RCU user mode
@ 2012-10-10 23:48 Frederic Weisbecker
2012-10-11 0:50 ` Paul E. McKenney
0 siblings, 1 reply; 2+ messages in thread
From: Frederic Weisbecker @ 2012-10-10 23:48 UTC (permalink / raw)
To: Paul E. McKenney; +Cc: LKML, Frederic Weisbecker
Discourage distros from enabling CONFIG_RCU_USER_QS
because it brings overhead for no benefits yet.
It's not a useful feature on its own until we can
fully run an adaptive tickless kernel.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
init/Kconfig | 12 ++++++++++++
1 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig
index c26b8a1..89093e1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -451,6 +451,12 @@ config RCU_USER_QS
excluded from the global RCU state machine and thus doesn't
to keep the timer tick on for RCU.
+ Unless you want to hack and help the development of the full
+ tickless feature, you shouldn't enable this option. It adds
+ unnecessary overhead.
+
+ If unsure say N
+
config RCU_USER_QS_FORCE
bool "Force userspace extended QS by default"
depends on RCU_USER_QS
@@ -459,6 +465,12 @@ config RCU_USER_QS_FORCE
test this feature that treats userspace as an extended quiescent
state until we have a real user like a full adaptive nohz option.
+ Unless you want to hack and help the development of the full
+ tickless feature, you shouldn't enable this option. It adds
+ unnecessary overhead.
+
+ If unsure say N
+
config RCU_FANOUT
int "Tree-based hierarchical RCU fanout value"
range 2 64 if 64BIT
--
1.7.5.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] rcu: Advise most users not to enable RCU user mode
2012-10-10 23:48 [PATCH] rcu: Advise most users not to enable RCU user mode Frederic Weisbecker
@ 2012-10-11 0:50 ` Paul E. McKenney
0 siblings, 0 replies; 2+ messages in thread
From: Paul E. McKenney @ 2012-10-11 0:50 UTC (permalink / raw)
To: Frederic Weisbecker; +Cc: Paul E. McKenney, LKML
On Thu, Oct 11, 2012 at 01:48:28AM +0200, Frederic Weisbecker wrote:
> Discourage distros from enabling CONFIG_RCU_USER_QS
> because it brings overhead for no benefits yet.
>
> It's not a useful feature on its own until we can
> fully run an adaptive tickless kernel.
Queued, hopefully for 3.7, thank you!
Thanx, Paul
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> ---
> init/Kconfig | 12 ++++++++++++
> 1 files changed, 12 insertions(+), 0 deletions(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index c26b8a1..89093e1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -451,6 +451,12 @@ config RCU_USER_QS
> excluded from the global RCU state machine and thus doesn't
> to keep the timer tick on for RCU.
>
> + Unless you want to hack and help the development of the full
> + tickless feature, you shouldn't enable this option. It adds
> + unnecessary overhead.
> +
> + If unsure say N
> +
> config RCU_USER_QS_FORCE
> bool "Force userspace extended QS by default"
> depends on RCU_USER_QS
> @@ -459,6 +465,12 @@ config RCU_USER_QS_FORCE
> test this feature that treats userspace as an extended quiescent
> state until we have a real user like a full adaptive nohz option.
>
> + Unless you want to hack and help the development of the full
> + tickless feature, you shouldn't enable this option. It adds
> + unnecessary overhead.
> +
> + If unsure say N
> +
> config RCU_FANOUT
> int "Tree-based hierarchical RCU fanout value"
> range 2 64 if 64BIT
> --
> 1.7.5.4
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2012-10-11 0:50 ` Paul E. McKenney
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