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SubjectRe: [RESEND, PATCH 6/6] memcg: cleanup memcg_check_events()
On Fri, Jan 06, 2012 at 10:57:52PM +0200, Kirill A. Shutemov wrote:
> From: "Kirill A. Shutemov" <kirill@shutemov.name>
>
> Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
> ---
> mm/memcontrol.c | 42 ++++++++++++++++++++++++------------------
> 1 files changed, 24 insertions(+), 18 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2eddcb5..0a13afa 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -108,11 +108,12 @@ enum mem_cgroup_events_index {
> * than using jiffies etc. to handle periodic memcg event.
> */
> enum mem_cgroup_events_target {
> - MEM_CGROUP_TARGET_THRESH,
> - MEM_CGROUP_TARGET_SOFTLIMIT,
> - MEM_CGROUP_TARGET_NUMAINFO,
> - MEM_CGROUP_NTARGETS,
> + MEM_CGROUP_TARGET_THRESH = BIT(1),
> + MEM_CGROUP_TARGET_SOFTLIMIT = BIT(2),
> + MEM_CGROUP_TARGET_NUMAINFO = BIT(3),
> };
> +#define MEM_CGROUP_NTARGETS 3

That really asks for the next guy forgetting to increase the number
when adding another bit.

> @@ -734,7 +735,7 @@ static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg,
> return total;
> }
>
> -static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> +static int mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> enum mem_cgroup_events_target target)
> {
> unsigned long val, next;
> @@ -757,9 +758,9 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> break;
> }
> __this_cpu_write(memcg->stat->targets[target], next);
> - return true;
> + return target;
> }
> - return false;
> + return 0;

Really weird interface - I'll return what you passed in, or zero...?

> @@ -768,29 +769,34 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> */
> static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
> {
> + int flags;
> +
> preempt_disable();
> - /* threshold event is triggered in finer grain than soft limit */
> - if (unlikely(mem_cgroup_event_ratelimit(memcg,
> - MEM_CGROUP_TARGET_THRESH))) {
> - bool do_softlimit, do_numainfo;
> + flags = mem_cgroup_event_ratelimit(memcg, MEM_CGROUP_TARGET_THRESH);
>
> - do_softlimit = mem_cgroup_event_ratelimit(memcg,
> + /*
> + * Threshold event is triggered in finer grain than soft limit
> + * and numainfo
> + */
> + if (unlikely(flags)) {
> + flags |= mem_cgroup_event_ratelimit(memcg,
> MEM_CGROUP_TARGET_SOFTLIMIT);
> #if MAX_NUMNODES > 1
> - do_numainfo = mem_cgroup_event_ratelimit(memcg,
> + flags |= mem_cgroup_event_ratelimit(memcg,
> MEM_CGROUP_TARGET_NUMAINFO);
> #endif
> - preempt_enable();
> + }
> + preempt_enable();
>
> + if (unlikely(flags)) {
> mem_cgroup_threshold(memcg);
> - if (unlikely(do_softlimit))
> + if (unlikely(flags & MEM_CGROUP_TARGET_SOFTLIMIT))
> mem_cgroup_update_tree(memcg, page);
> #if MAX_NUMNODES > 1
> - if (unlikely(do_numainfo))
> + if (unlikely(flags & MEM_CGROUP_TARGET_NUMAINFO))
> atomic_inc(&memcg->numainfo_events);
> #endif
> - } else
> - preempt_enable();
> + }
> }

I'm about to remove the soft limit part of this code, so we'll be able
to condense this back into a single #if block again, anyway.

I would much prefer having the extra #if in the code over this patch
just to silence the warning for now.


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