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Message-ID: <661de9470909021315m3af0de32h29f1ac8fd574249d@mail.gmail.com>
Date: Thu, 3 Sep 2009 01:45:06 +0530
From: Balbir Singh <balbir@...ux.vnet.ibm.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [mmotm][PATCH 2/2 v2] memcg: reduce calls for soft limit excess
On Wed, Sep 2, 2009 at 11:26 AM, KAMEZAWA
Hiroyuki<kamezawa.hiroyu@...fujitsu.com> wrote:
> In charge/uncharge/reclaim path, usage_in_excess is calculated repeatedly and
> it takes res_counter's spin_lock every time.
>
I think the changelog needs to mention some refactoring you've done
below as well, like change new_charge_in_excess to excess.
> This patch removes unnecessary calls for res_count_soft_limit_excess.
>
> Changelog:
> - fixed description.
> - fixed unsigned long to be unsigned long long (Thanks, Nishimura)
>
> Reviewed-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
> mm/memcontrol.c | 31 +++++++++++++++----------------
> 1 file changed, 15 insertions(+), 16 deletions(-)
>
> Index: mmotm-2.6.31-Aug27/mm/memcontrol.c
> ===================================================================
> --- mmotm-2.6.31-Aug27.orig/mm/memcontrol.c
> +++ mmotm-2.6.31-Aug27/mm/memcontrol.c
> @@ -313,7 +313,8 @@ soft_limit_tree_from_page(struct page *p
> static void
> __mem_cgroup_insert_exceeded(struct mem_cgroup *mem,
> struct mem_cgroup_per_zone *mz,
> - struct mem_cgroup_tree_per_zone *mctz)
> + struct mem_cgroup_tree_per_zone *mctz,
> + unsigned long long new_usage_in_excess)
> {
> struct rb_node **p = &mctz->rb_root.rb_node;
> struct rb_node *parent = NULL;
> @@ -322,7 +323,9 @@ __mem_cgroup_insert_exceeded(struct mem_
> if (mz->on_tree)
> return;
>
> - mz->usage_in_excess = res_counter_soft_limit_excess(&mem->res);
> + mz->usage_in_excess = new_usage_in_excess;
> + if (!mz->usage_in_excess)
> + return;
> while (*p) {
> parent = *p;
> mz_node = rb_entry(parent, struct mem_cgroup_per_zone,
> @@ -382,7 +385,7 @@ static bool mem_cgroup_soft_limit_check(
>
> static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page)
> {
> - unsigned long long new_usage_in_excess;
> + unsigned long long excess;
> struct mem_cgroup_per_zone *mz;
> struct mem_cgroup_tree_per_zone *mctz;
> int nid = page_to_nid(page);
> @@ -395,25 +398,21 @@ static void mem_cgroup_update_tree(struc
> */
> for (; mem; mem = parent_mem_cgroup(mem)) {
> mz = mem_cgroup_zoneinfo(mem, nid, zid);
> - new_usage_in_excess =
> - res_counter_soft_limit_excess(&mem->res);
> + excess = res_counter_soft_limit_excess(&mem->res);
> /*
> * We have to update the tree if mz is on RB-tree or
> * mem is over its softlimit.
> */
> - if (new_usage_in_excess || mz->on_tree) {
> + if (excess || mz->on_tree) {
> spin_lock(&mctz->lock);
> /* if on-tree, remove it */
> if (mz->on_tree)
> __mem_cgroup_remove_exceeded(mem, mz, mctz);
> /*
> - * if over soft limit, insert again. mz->usage_in_excess
> - * will be updated properly.
> + * Insert again. mz->usage_in_excess will be updated.
> + * If excess is 0, no tree ops.
> */
> - if (new_usage_in_excess)
> - __mem_cgroup_insert_exceeded(mem, mz, mctz);
> - else
> - mz->usage_in_excess = 0;
> + __mem_cgroup_insert_exceeded(mem, mz, mctz, excess);
> spin_unlock(&mctz->lock);
> }
> }
> @@ -2216,6 +2215,7 @@ unsigned long mem_cgroup_soft_limit_recl
> unsigned long reclaimed;
> int loop = 0;
> struct mem_cgroup_tree_per_zone *mctz;
> + unsigned long long excess;
>
> if (order > 0)
> return 0;
> @@ -2260,9 +2260,8 @@ unsigned long mem_cgroup_soft_limit_recl
> __mem_cgroup_largest_soft_limit_node(mctz);
> } while (next_mz == mz);
> }
> - mz->usage_in_excess =
> - res_counter_soft_limit_excess(&mz->mem->res);
> __mem_cgroup_remove_exceeded(mz->mem, mz, mctz);
> + excess = res_counter_soft_limit_excess(&mz->mem->res);
> /*
> * One school of thought says that we should not add
> * back the node to the tree if reclaim returns 0.
> @@ -2271,8 +2270,8 @@ unsigned long mem_cgroup_soft_limit_recl
> * memory to reclaim from. Consider this as a longer
> * term TODO.
> */
> - if (mz->usage_in_excess)
> - __mem_cgroup_insert_exceeded(mz->mem, mz, mctz);
> + /* If excess == 0, no tree ops */
> + __mem_cgroup_insert_exceeded(mz->mem, mz, mctz, excess);
> spin_unlock(&mctz->lock);
> css_put(&mz->mem->css);
> loop++;
OK.. so everytime we call __mem_cgroup_insert_exceeded we save one
res_counter operation.
Looks good
Acked-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
Balbir Singh
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