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authorBalbir Singh <balbir@linux.vnet.ibm.com>2008-04-29 01:00:16 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 08:06:10 -0700
commitcf475ad28ac35cc9ba612d67158f29b73b38b05d (patch)
tree2c7cd568d00357bd42643ea602884e731cc24f26 /kernel/exit.c
parent29486df325e1fe6e1764afcb19e3370804c2b002 (diff)
cgroups: add an owner to the mm_struct
Remove the mem_cgroup member from mm_struct and instead adds an owner. This approach was suggested by Paul Menage. The advantage of this approach is that, once the mm->owner is known, using the subsystem id, the cgroup can be determined. It also allows several control groups that are virtually grouped by mm_struct, to exist independent of the memory controller i.e., without adding mem_cgroup's for each controller, to mm_struct. A new config option CONFIG_MM_OWNER is added and the memory resource controller selects this config option. This patch also adds cgroup callbacks to notify subsystems when mm->owner changes. The mm_cgroup_changed callback is called with the task_lock() of the new task held and is called just prior to changing the mm->owner. I am indebted to Paul Menage for the several reviews of this patchset and helping me make it lighter and simpler. This patch was tested on a powerpc box, it was compiled with both the MM_OWNER config turned on and off. After the thread group leader exits, it's moved to init_css_state by cgroup_exit(), thus all future charges from runnings threads would be redirected to the init_css_set's subsystem. Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Pavel Emelianov <xemul@openvz.org> Cc: Hugh Dickins <hugh@veritas.com> Cc: Sudhir Kumar <skumar@linux.vnet.ibm.com> Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp> Cc: Hirokazu Takahashi <taka@valinux.co.jp> Cc: David Rientjes <rientjes@google.com>, Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Reviewed-by: Paul Menage <menage@google.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r--kernel/exit.c83
1 files changed, 83 insertions, 0 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 2a9d98c641a..ae0f2c4e452 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -557,6 +557,88 @@ void exit_fs(struct task_struct *tsk)
EXPORT_SYMBOL_GPL(exit_fs);
+#ifdef CONFIG_MM_OWNER
+/*
+ * Task p is exiting and it owned mm, lets find a new owner for it
+ */
+static inline int
+mm_need_new_owner(struct mm_struct *mm, struct task_struct *p)
+{
+ /*
+ * If there are other users of the mm and the owner (us) is exiting
+ * we need to find a new owner to take on the responsibility.
+ */
+ if (!mm)
+ return 0;
+ if (atomic_read(&mm->mm_users) <= 1)
+ return 0;
+ if (mm->owner != p)
+ return 0;
+ return 1;
+}
+
+void mm_update_next_owner(struct mm_struct *mm)
+{
+ struct task_struct *c, *g, *p = current;
+
+retry:
+ if (!mm_need_new_owner(mm, p))
+ return;
+
+ read_lock(&tasklist_lock);
+ /*
+ * Search in the children
+ */
+ list_for_each_entry(c, &p->children, sibling) {
+ if (c->mm == mm)
+ goto assign_new_owner;
+ }
+
+ /*
+ * Search in the siblings
+ */
+ list_for_each_entry(c, &p->parent->children, sibling) {
+ if (c->mm == mm)
+ goto assign_new_owner;
+ }
+
+ /*
+ * Search through everything else. We should not get
+ * here often
+ */
+ do_each_thread(g, c) {
+ if (c->mm == mm)
+ goto assign_new_owner;
+ } while_each_thread(g, c);
+
+ read_unlock(&tasklist_lock);
+ return;
+
+assign_new_owner:
+ BUG_ON(c == p);
+ get_task_struct(c);
+ /*
+ * The task_lock protects c->mm from changing.
+ * We always want mm->owner->mm == mm
+ */
+ task_lock(c);
+ /*
+ * Delay read_unlock() till we have the task_lock()
+ * to ensure that c does not slip away underneath us
+ */
+ read_unlock(&tasklist_lock);
+ if (c->mm != mm) {
+ task_unlock(c);
+ put_task_struct(c);
+ goto retry;
+ }
+ cgroup_mm_owner_callbacks(mm->owner, c);
+ mm->owner = c;
+ task_unlock(c);
+ put_task_struct(c);
+}
+#endif /* CONFIG_MM_OWNER */
+
/*
* Turn us into a lazy TLB process if we
* aren't already..
@@ -596,6 +678,7 @@ static void exit_mm(struct task_struct * tsk)
/* We don't want this task to be frozen prematurely */
clear_freeze_flag(tsk);
task_unlock(tsk);
+ mm_update_next_owner(mm);
mmput(mm);
}