[PATCH] slab: use deferable timers for its periodic housekeeping

[PATCH] slab: use deferable timers for its periodic housekeeping

[Arjan van de Ven]

From: Arjan van de Ven <arjan@linux.intel.com>
Subject: [PATCH] slab: use deferable timers for its periodic housekeeping

slab has a "once every 2 second" timer for its housekeeping.
As the number of logical processors is growing, its more and more
common that this 2 second timer becomes the primary wakeup source.

This patch turns this housekeeping timer into a deferable timer,
which means that the timer does not interrupt idle, but just runs
at the next event that wakes the cpu up.

The impact is that the timer likely runs a bit later, but during the
delay no code is running so there's not all that much reason for
a difference in housekeeping to occur because of this delay.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
  mm/slab.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 7451bda..ef3cd3d 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -884,7 +884,7 @@ static void __cpuinit start_cpu_timer(int cpu)
       */
      if (keventd_up() && reap_work->work.func == NULL) {
          init_reap_node(cpu);
-        INIT_DELAYED_WORK(reap_work, cache_reap);
+        INIT_DELAYED_WORK_DEFERRABLE(reap_work, cache_reap);
          schedule_delayed_work_on(cpu, reap_work,
                      __round_jiffies_relative(HZ, cpu));
      }
-- 
1.6.1.3

Re: [PATCH] slab: use deferable timers for its periodic housekeeping

[Pekka Enberg]

Arjan van de Ven wrote:
> From: Arjan van de Ven <arjan@linux.intel.com>
> Subject: [PATCH] slab: use deferable timers for its periodic housekeeping
> 
> slab has a "once every 2 second" timer for its housekeeping.
> As the number of logical processors is growing, its more and more
> common that this 2 second timer becomes the primary wakeup source.
> 
> This patch turns this housekeeping timer into a deferable timer,
> which means that the timer does not interrupt idle, but just runs
> at the next event that wakes the cpu up.
> 
> The impact is that the timer likely runs a bit later, but during the
> delay no code is running so there's not all that much reason for
> a difference in housekeeping to occur because of this delay.
> 
> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
> ---
>  mm/slab.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/slab.c b/mm/slab.c
> index 7451bda..ef3cd3d 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -884,7 +884,7 @@ static void __cpuinit start_cpu_timer(int cpu)
>       */
>      if (keventd_up() && reap_work->work.func == NULL) {
>          init_reap_node(cpu);
> -        INIT_DELAYED_WORK(reap_work, cache_reap);
> +        INIT_DELAYED_WORK_DEFERRABLE(reap_work, cache_reap);
>          schedule_delayed_work_on(cpu, reap_work,
>                      __round_jiffies_relative(HZ, cpu));
>      }

[ The patch seems to have been whitespace damaged. ]

Applied, thanks!