diff options
| author |   Paul Menage <menage@google.com> | 2009-01-29 14:25:21 -0800 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-29 18:04:45 -0800 |
| commit | 804b3c28a4e4fa1c224571bf76edb534b9c4b1ed (patch) | |
| tree | 59e0dabb227a5067cfdc7cce13f149f141ef8cb4 | |
| parent | cgroups: fix lock inconsistency in cgroup_clone() (diff) | |
| download | linux-dev-804b3c28a4e4fa1c224571bf76edb534b9c4b1ed.tar.xz linux-dev-804b3c28a4e4fa1c224571bf76edb534b9c4b1ed.zip | |
cgroups: add cpu_relax() calls in css_tryget() and cgroup_clear_css_refs()
css_tryget() and cgroup_clear_css_refs() contain polling loops; these
loops should have cpu_relax calls in them to reduce cross-cache traffic.
Signed-off-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/cgroup.h | 1 | ||||
| -rw-r--r-- | kernel/cgroup.c | 7 |
2 files changed, 6 insertions, 2 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index e267e62827bb..e4e8e117d27d 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -99,6 +99,7 @@ static inline bool css_tryget(struct cgroup_subsys_state *css) while (!atomic_inc_not_zero(&css->refcnt)) { if (test_bit(CSS_REMOVED, &css->flags)) return false; + cpu_relax(); } return true; } diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 0066092de19a..492215d67fa5 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2509,7 +2509,7 @@ static int cgroup_clear_css_refs(struct cgroup *cgrp) for_each_subsys(cgrp->root, ss) { struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id]; int refcnt; - do { + while (1) { /* We can only remove a CSS with a refcnt==1 */ refcnt = atomic_read(&css->refcnt); if (refcnt > 1) { @@ -2523,7 +2523,10 @@ static int cgroup_clear_css_refs(struct cgroup *cgrp) * css_tryget() to spin until we set the * CSS_REMOVED bits or abort */ - } while (atomic_cmpxchg(&css->refcnt, refcnt, 0) != refcnt); + if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt) + break; + cpu_relax(); + } } done: for_each_subsys(cgrp->root, ss) { |