From d7b9fff711d5e8db8c844161c684017e556c38a0 Mon Sep 17 00:00:00 2001 From: Daisuke Nishimura Date: Wed, 10 Mar 2010 15:22:05 -0800 Subject: [PATCH] cgroup: introduce coalesce css_get() and css_put() Current css_get() and css_put() increment/decrement css->refcnt one by one. This patch add a new function __css_get(), which takes "count" as a arg and increment the css->refcnt by "count". And this patch also add a new arg("count") to __css_put() and change the function to decrement the css->refcnt by "count". These coalesce version of __css_get()/__css_put() will be used to improve performance of memcg's moving charge feature later, where instead of calling css_get()/css_put() repeatedly, these new functions will be used. No change is needed for current users of css_get()/css_put(). Signed-off-by: Daisuke Nishimura Acked-by: Paul Menage Cc: Balbir Singh Acked-by: KAMEZAWA Hiroyuki Cc: Li Zefan Cc: Daisuke Nishimura Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cgroup.h | 12 +++++++++--- kernel/cgroup.c | 5 +++-- 2 files changed, 12 insertions(+), 5 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index d08cfe7e12e5..14160b5b693f 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -76,6 +76,12 @@ enum { CSS_REMOVED, /* This CSS is dead */ }; +/* Caller must verify that the css is not for root cgroup */ +static inline void __css_get(struct cgroup_subsys_state *css, int count) +{ + atomic_add(count, &css->refcnt); +} + /* * Call css_get() to hold a reference on the css; it can be used * for a reference obtained via: @@ -87,7 +93,7 @@ static inline void css_get(struct cgroup_subsys_state *css) { /* We don't need to reference count the root state */ if (!test_bit(CSS_ROOT, &css->flags)) - atomic_inc(&css->refcnt); + __css_get(css, 1); } static inline bool css_is_removed(struct cgroup_subsys_state *css) @@ -118,11 +124,11 @@ static inline bool css_tryget(struct cgroup_subsys_state *css) * css_get() or css_tryget() */ -extern void __css_put(struct cgroup_subsys_state *css); +extern void __css_put(struct cgroup_subsys_state *css, int count); static inline void css_put(struct cgroup_subsys_state *css) { if (!test_bit(CSS_ROOT, &css->flags)) - __css_put(css); + __css_put(css, 1); } /* bits in struct cgroup flags field */ diff --git a/kernel/cgroup.c b/kernel/cgroup.c index be45d2f6008a..cace83ddbcdc 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3746,12 +3746,13 @@ static void check_for_release(struct cgroup *cgrp) } } -void __css_put(struct cgroup_subsys_state *css) +/* Caller must verify that the css is not for root cgroup */ +void __css_put(struct cgroup_subsys_state *css, int count) { struct cgroup *cgrp = css->cgroup; int val; rcu_read_lock(); - val = atomic_dec_return(&css->refcnt); + val = atomic_sub_return(count, &css->refcnt); if (val == 1) { if (notify_on_release(cgrp)) { set_bit(CGRP_RELEASABLE, &cgrp->flags); -- 2.20.1