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authorDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>2010-03-10 15:22:05 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-12 15:52:36 -0800
commitd7b9fff711d5e8db8c844161c684017e556c38a0 (patch)
treefea09ff79fe543edc2d8c0e85d35de1b2c783f2d
parent2468c7234b366eeb799ee0648cb58f9cba394a54 (diff)
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>
-rw-r--r--include/linux/cgroup.h12
-rw-r--r--kernel/cgroup.c5
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);