The patch titled
cgroup: introduce coalesce css_get() and css_put()
has been added to the -mm tree. Its filename is
cgroup-introduce-coalesce-css_get-and-css_put.patch
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Subject: cgroup: introduce coalesce css_get() and css_put()
From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxx>
Acked-by: Paul Menage <menage@xxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/cgroup.h | 12 +++++++++---
kernel/cgroup.c | 5 +++--
2 files changed, 12 insertions(+), 5 deletions(-)
diff -puN include/linux/cgroup.h~cgroup-introduce-coalesce-css_get-and-css_put include/linux/cgroup.h
--- a/include/linux/cgroup.h~cgroup-introduce-coalesce-css_get-and-css_put
+++ a/include/linux/cgroup.h
@@ -75,6 +75,12 @@ 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:
@@ -86,7 +92,7 @@ static inline void css_get(struct cgroup
{
/* 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)
@@ -117,11 +123,11 @@ static inline bool css_tryget(struct cgr
* 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 -puN kernel/cgroup.c~cgroup-introduce-coalesce-css_get-and-css_put kernel/cgroup.c
--- a/kernel/cgroup.c~cgroup-introduce-coalesce-css_get-and-css_put
+++ a/kernel/cgroup.c
@@ -3729,12 +3729,13 @@ static void check_for_release(struct cgr
}
}
-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);
_
Patches currently in -mm which might be from nishimura@xxxxxxxxxxxxxxxxx are
cgroup-introduce-cancel_attach.patch
cgroup-introduce-coalesce-css_get-and-css_put.patch
memcg-add-interface-to-move-charge-at-task-migration.patch
memcg-move-charges-of-anonymous-page.patch
memcg-move-charges-of-anonymous-page-cleanup.patch
memcg-improve-performance-in-moving-charge.patch
memcg-avoid-oom-during-moving-charge.patch
memcg-move-charges-of-anonymous-swap.patch
memcg-improve-performance-in-moving-swap-charge.patch
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