From: Josh Triplett <josh@joshtriplett.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
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
Subject: Re: [PATCH tip/core/rcu 2/2] rcu: Allow TREE_PREEMPT_RCU on UP systems
Date: Sun, 27 Jan 2013 21:58:06 +1100 [thread overview]
Message-ID: <20130127105805.GE3119@leaf> (raw)
In-Reply-To: <1359246227-5770-2-git-send-email-paulmck@linux.vnet.ibm.com>
On Sat, Jan 26, 2013 at 04:23:47PM -0800, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>
> The TINY_PREEMPT_RCU is complex, does not provide that much memory
> savings, and therefore TREE_PREEMPT_RCU should be used instead. The
> systems where the difference between TINY_PREEMPT_RCU and TREE_PREEMPT_RCU
> are quite small compared to the memory footprint of CONFIG_PREEMPT.
>
> This commit therefore takes a first step towards eliminating
> TINY_PREEMPT_RCU by allowing TREE_PREEMPT_RCU to be configured on !SMP
> systems.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
> ---
> init/Kconfig | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index a5e90e1..fb19b46 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -453,7 +453,7 @@ config TREE_RCU
>
> config TREE_PREEMPT_RCU
> bool "Preemptible tree-based hierarchical RCU"
> - depends on PREEMPT && SMP
> + depends on PREEMPT
> help
> This option selects the RCU implementation that is
> designed for very large SMP systems with hundreds or
> @@ -461,6 +461,8 @@ config TREE_PREEMPT_RCU
> is also required. It also scales down nicely to
> smaller systems.
>
> + Select this option if you are unsure.
> +
> config TINY_RCU
> bool "UP-only small-memory-footprint RCU"
> depends on !PREEMPT && !SMP
> --
> 1.7.8
>
next prev parent reply other threads:[~2013-01-27 10:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-27 0:23 [PATCH tip/core/rcu 0/2] v2 Tiny RCU changes for 3.9 Paul E. McKenney
2013-01-27 0:23 ` [PATCH tip/core/rcu 1/2] rcu: Provide RCU CPU stall warnings for tiny RCU Paul E. McKenney
2013-01-27 0:23 ` [PATCH tip/core/rcu 2/2] rcu: Allow TREE_PREEMPT_RCU on UP systems Paul E. McKenney
2013-01-27 10:58 ` Josh Triplett [this message]
2013-01-27 10:57 ` [PATCH tip/core/rcu 1/2] rcu: Provide RCU CPU stall warnings for tiny RCU Josh Triplett
2013-01-29 5:56 ` Paul E. McKenney
2013-01-27 10:58 ` [PATCH tip/core/rcu 0/2] v2 Tiny RCU changes for 3.9 Josh Triplett
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