On Wed, 30 Dec 2009 17:57:58 +0200
"Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote:
> Instead of incrementing counter on each page in/out and comparing it
> with constant, we set counter to constant, decrement counter on each
> page in/out and compare it with zero. We want to make comparing as fast
> as possible. On many RISC systems (probably not only RISC) comparing
> with zero is more effective than comparing with a constant, since not
> every constant can be immediate operand for compare instruction.
>
> Also, I've renamed MEM_CGROUP_STAT_EVENTS to MEM_CGROUP_STAT_SOFTLIMIT,
> since really it's not a generic counter.
>
> Signed-off-by: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
>
> KAMEZAWA-san, I've changed the patch a bit. Can I reuse your Acked-by?
>
> ---
> mm/memcontrol.c | 18 ++++++++++--------
> 1 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1d71cb4..c36d4f3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -69,8 +69,9 @@ enum mem_cgroup_stat_index {
> MEM_CGROUP_STAT_FILE_MAPPED, /* # of pages charged as file rss */
> MEM_CGROUP_STAT_PGPGIN_COUNT, /* # of pages paged in */
> MEM_CGROUP_STAT_PGPGOUT_COUNT, /* # of pages paged out */
> - MEM_CGROUP_STAT_EVENTS, /* sum of pagein + pageout for internal use */
> MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
> + MEM_CGROUP_STAT_SOFTLIMIT, /* decrements on each page in/out.
> + used by soft limit implementation */
>
> MEM_CGROUP_STAT_NSTATS,
> };
> @@ -84,10 +85,10 @@ struct mem_cgroup_stat {
> };
>
> static inline void
> -__mem_cgroup_stat_reset_safe(struct mem_cgroup_stat_cpu *stat,
> - enum mem_cgroup_stat_index idx)
> +__mem_cgroup_stat_set_safe(struct mem_cgroup_stat_cpu *stat,
> + enum mem_cgroup_stat_index idx, s64 val)
> {
> - stat->count[idx] = 0;
> + stat->count[idx] = val;
> }
>
> static inline s64
> @@ -380,9 +381,10 @@ static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem)
>
> cpu = get_cpu();
> cpustat = &mem->stat.cpustat[cpu];
> - val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
> - if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
> - __mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
> + val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_SOFTLIMIT);
> + if (unlikely(val < 0)) {
> + __mem_cgroup_stat_set_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT,
> + SOFTLIMIT_EVENTS_THRESH);
> ret = true;
> }
> put_cpu();
> @@ -515,7 +517,7 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
> else
> __mem_cgroup_stat_add_safe(cpustat,
> MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
> - __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_EVENTS, 1);
> + __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT, -1);
> put_cpu();
> }
>
> --
> 1.6.5.7
>
>
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