The patch titled
Subject: memcg: remove PCG_MOVE_LOCK flag from page_cgroup
has been removed from the -mm tree. Its filename was
memcg-remove-pcg_move_lock-flag-from-page_cgroup.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Subject: memcg: remove PCG_MOVE_LOCK flag from page_cgroup
PCG_MOVE_LOCK is used for bit spinlock to avoid race between overwriting
pc->mem_cgroup and page statistics accounting per memcg. This lock helps
to avoid the race but the race is very rare because moving tasks between
cgroup is not a usual job. So, it seems using 1bit per page is too
costly.
This patch changes this lock as per-memcg spinlock and removes
PCG_MOVE_LOCK.
If smaller lock is required, we'll be able to add some hashes but I'd like
to start from this.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Ying Han <yinghan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/page_cgroup.h | 19 ---------------
mm/memcontrol.c | 42 +++++++++++++++++++++++++---------
2 files changed, 32 insertions(+), 29 deletions(-)
diff -puN include/linux/page_cgroup.h~memcg-remove-pcg_move_lock-flag-from-page_cgroup include/linux/page_cgroup.h
--- a/include/linux/page_cgroup.h~memcg-remove-pcg_move_lock-flag-from-page_cgroup
+++ a/include/linux/page_cgroup.h
@@ -7,7 +7,6 @@ enum {
PCG_USED, /* this object is in use. */
PCG_MIGRATION, /* under page migration */
/* flags for mem_cgroup and file and I/O status */
- PCG_MOVE_LOCK, /* For race between move_account v.s. following bits */
PCG_FILE_MAPPED, /* page is accounted as "mapped" */
__NR_PCG_FLAGS,
};
@@ -89,24 +88,6 @@ static inline void unlock_page_cgroup(st
bit_spin_unlock(PCG_LOCK, &pc->flags);
}
-static inline void move_lock_page_cgroup(struct page_cgroup *pc,
- unsigned long *flags)
-{
- /*
- * We know updates to pc->flags of page cache's stats are from both of
- * usual context or IRQ context. Disable IRQ to avoid deadlock.
- */
- local_irq_save(*flags);
- bit_spin_lock(PCG_MOVE_LOCK, &pc->flags);
-}
-
-static inline void move_unlock_page_cgroup(struct page_cgroup *pc,
- unsigned long *flags)
-{
- bit_spin_unlock(PCG_MOVE_LOCK, &pc->flags);
- local_irq_restore(*flags);
-}
-
#else /* CONFIG_CGROUP_MEM_RES_CTLR */
struct page_cgroup;
diff -puN mm/memcontrol.c~memcg-remove-pcg_move_lock-flag-from-page_cgroup mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-remove-pcg_move_lock-flag-from-page_cgroup
+++ a/mm/memcontrol.c
@@ -300,6 +300,8 @@ struct mem_cgroup {
* set > 0 if pages under this cgroup are moving to other cgroup.
*/
atomic_t moving_account;
+ /* taken only while moving_account > 0 */
+ spinlock_t move_lock;
/*
* percpu counter.
*/
@@ -1376,6 +1378,24 @@ static bool mem_cgroup_wait_acct_move(st
return false;
}
+/*
+ * Take this lock when
+ * - a code tries to modify page's memcg while it's USED.
+ * - a code tries to modify page state accounting in a memcg.
+ * see mem_cgroup_stealed(), too.
+ */
+static void move_lock_mem_cgroup(struct mem_cgroup *memcg,
+ unsigned long *flags)
+{
+ spin_lock_irqsave(&memcg->move_lock, *flags);
+}
+
+static void move_unlock_mem_cgroup(struct mem_cgroup *memcg,
+ unsigned long *flags)
+{
+ spin_unlock_irqrestore(&memcg->move_lock, *flags);
+}
+
/**
* mem_cgroup_print_oom_info: Called from OOM with tasklist_lock held in read mode.
* @memcg: The memory cgroup that went over limit
@@ -1900,7 +1920,7 @@ void mem_cgroup_update_page_stat(struct
if (mem_cgroup_disabled())
return;
-
+again:
rcu_read_lock();
memcg = pc->mem_cgroup;
if (unlikely(!memcg || !PageCgroupUsed(pc)))
@@ -1908,11 +1928,13 @@ void mem_cgroup_update_page_stat(struct
/* pc->mem_cgroup is unstable ? */
if (unlikely(mem_cgroup_stealed(memcg))) {
/* take a lock against to access pc->mem_cgroup */
- move_lock_page_cgroup(pc, &flags);
+ move_lock_mem_cgroup(memcg, &flags);
+ if (memcg != pc->mem_cgroup || !PageCgroupUsed(pc)) {
+ move_unlock_mem_cgroup(memcg, &flags);
+ rcu_read_unlock();
+ goto again;
+ }
need_unlock = true;
- memcg = pc->mem_cgroup;
- if (!memcg || !PageCgroupUsed(pc))
- goto out;
}
switch (idx) {
@@ -1931,7 +1953,7 @@ void mem_cgroup_update_page_stat(struct
out:
if (unlikely(need_unlock))
- move_unlock_page_cgroup(pc, &flags);
+ move_unlock_mem_cgroup(memcg, &flags);
rcu_read_unlock();
}
@@ -2500,8 +2522,7 @@ static void __mem_cgroup_commit_charge(s
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-#define PCGF_NOCOPY_AT_SPLIT ((1 << PCG_LOCK) | (1 << PCG_MOVE_LOCK) |\
- (1 << PCG_MIGRATION))
+#define PCGF_NOCOPY_AT_SPLIT ((1 << PCG_LOCK) | (1 << PCG_MIGRATION))
/*
* Because tail pages are not marked as "used", set it. We're under
* zone->lru_lock, 'splitting on pmd' and compound_lock.
@@ -2572,7 +2593,7 @@ static int mem_cgroup_move_account(struc
if (!PageCgroupUsed(pc) || pc->mem_cgroup != from)
goto unlock;
- move_lock_page_cgroup(pc, &flags);
+ move_lock_mem_cgroup(from, &flags);
if (PageCgroupFileMapped(pc)) {
/* Update mapped_file data for mem_cgroup */
@@ -2596,7 +2617,7 @@ static int mem_cgroup_move_account(struc
* guaranteed that "to" is never removed. So, we don't check rmdir
* status here.
*/
- move_unlock_page_cgroup(pc, &flags);
+ move_unlock_mem_cgroup(from, &flags);
ret = 0;
unlock:
unlock_page_cgroup(pc);
@@ -4971,6 +4992,7 @@ mem_cgroup_create(struct cgroup *cont)
atomic_set(&memcg->refcnt, 1);
memcg->move_charge_at_immigrate = 0;
mutex_init(&memcg->thresholds_lock);
+ spin_lock_init(&memcg->move_lock);
return &memcg->css;
free_out:
__mem_cgroup_free(memcg);
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
origin.patch
linux-next.patch
mm-hugetlb-cleanup-duplicated-code-in-unmapping-vm-range.patch
proc-speedup-proc-stat-handling.patch
procfs-add-num_to_str-to-speed-up-proc-stat.patch
procfs-add-num_to_str-to-speed-up-proc-stat-fix.patch
procfs-add-num_to_str-to-speed-up-proc-stat-fix-2.patch
procfs-speed-up-proc-pid-stat-statm.patch
procfs-speed-up-proc-pid-stat-statm-checkpatch-fixes.patch
seq_file-add-seq_set_overflow-seq_overflow.patch
seq_file-add-seq_set_overflow-seq_overflow-fix.patch
fs-proc-introduce-proc-pid-task-tid-children-entry-v9.patch
c-r-procfs-add-arg_start-end-env_start-end-and-exit_code-members-to-proc-pid-stat.patch
c-r-prctl-extend-pr_set_mm-to-set-up-more-mm_struct-entries-v2.patch
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