On Thu, 21 Jul 2011 09:38:00 +0200
Michal Hocko <mhocko@xxxxxxx> wrote:
> drain_all_stock_async tries to optimize a work to be done on the work
> queue by excluding any work for the current CPU because it assumes that
> the context we are called from already tried to charge from that cache
> and it's failed so it must be empty already.
> While the assumption is correct we can do it by checking the current
> number of pages in the cache. This will also reduce a work on other CPUs
> with an empty stock.
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
At the first look, when a charge against TransParentHugepage() goes
into the reclaim routine, stock->nr_pages != 0 and this will
call additional kworker.
nr_pages check itself seems good.
Thanks,
-Kame
> ---
> mm/memcontrol.c | 14 ++------------
> 1 files changed, 2 insertions(+), 12 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index f11f198..786bffb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2140,7 +2140,7 @@ static void refill_stock(struct mem_cgroup *mem, unsigned int nr_pages)
> */
> static void drain_all_stock_async(struct mem_cgroup *root_mem)
> {
> - int cpu, curcpu;
> + int cpu;
> /*
> * If someone calls draining, avoid adding more kworker runs.
> */
> @@ -2148,22 +2148,12 @@ static void drain_all_stock_async(struct mem_cgroup *root_mem)
> return;
> /* Notify other cpus that system-wide "drain" is running */
> get_online_cpus();
> - /*
> - * Get a hint for avoiding draining charges on the current cpu,
> - * which must be exhausted by our charging. It is not required that
> - * this be a precise check, so we use raw_smp_processor_id() instead of
> - * getcpu()/putcpu().
> - */
> - curcpu = raw_smp_processor_id();
> for_each_online_cpu(cpu) {
> struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
> struct mem_cgroup *mem;
>
> - if (cpu == curcpu)
> - continue;
> -
> mem = stock->cached;
> - if (!mem)
> + if (!mem || !stock->nr_pages)
> continue;
> if (mem != root_mem) {
> if (!root_mem->use_hierarchy)
> --
> 1.7.5.4
>
>
>
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