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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 <nishimura@mxp.nes.nec.co.jp>
Acked-by: Paul Menage <menage@google.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Daisuke Nishimura 2010-03-10 15:22:05 -08:00 committed by Linus Torvalds
parent 2468c7234b
commit d7b9fff711
2 changed files with 12 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
include/linux/cgroup.h
View File

@ -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 */

5
kernel/cgroup.c
View File

@ -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);