The patch titled
: change memcg_oom_mutex to spinlock
has been added to the -mm tree. Its filename is
memcg-change-memcg_oom_mutex-to-spinlock.patch
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------------------------------------------------------
Subject: : change memcg_oom_mutex to spinlock
From: Michal Hocko <mhocko@xxxxxxx>
memcg_oom_mutex is used to protect memcg OOM path and eventfd interface
for oom_control. None of the critical sections which it protects sleep
(eventfd_signal works from atomic context and the rest are simple linked
list resp. oom_lock atomic operations).
Mutex is also too heavyweight for those code paths because it triggers a
lot of scheduling. It also makes makes convoying effects more visible
when we have a big number of oom killing because we take the lock mutliple
times during mem_cgroup_handle_oom so we have multiple places where many
processes can sleep.
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff -puN mm/memcontrol.c~memcg-change-memcg_oom_mutex-to-spinlock mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-change-memcg_oom_mutex-to-spinlock
+++ a/mm/memcontrol.c
@@ -1724,7 +1724,7 @@ static int mem_cgroup_hierarchical_recla
/*
* Check OOM-Killer is already running under our hierarchy.
* If someone is running, return false.
- * Has to be called with memcg_oom_mutex
+ * Has to be called with memcg_oom_lock
*/
static bool mem_cgroup_oom_lock(struct mem_cgroup *mem)
{
@@ -1769,7 +1769,7 @@ done:
}
/*
- * Has to be called with memcg_oom_mutex
+ * Has to be called with memcg_oom_lock
*/
static int mem_cgroup_oom_unlock(struct mem_cgroup *mem)
{
@@ -1801,7 +1801,7 @@ static void mem_cgroup_unmark_under_oom(
atomic_add_unless(&iter->under_oom, -1, 0);
}
-static DEFINE_MUTEX(memcg_oom_mutex);
+static DEFINE_SPINLOCK(memcg_oom_lock);
static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
struct oom_wait_info {
@@ -1863,7 +1863,7 @@ bool mem_cgroup_handle_oom(struct mem_cg
mem_cgroup_mark_under_oom(mem);
/* At first, try to OOM lock hierarchy under mem.*/
- mutex_lock(&memcg_oom_mutex);
+ spin_lock(&memcg_oom_lock);
locked = mem_cgroup_oom_lock(mem);
/*
* Even if signal_pending(), we can't quit charge() loop without
@@ -1875,7 +1875,7 @@ bool mem_cgroup_handle_oom(struct mem_cg
need_to_kill = false;
if (locked)
mem_cgroup_oom_notify(mem);
- mutex_unlock(&memcg_oom_mutex);
+ spin_unlock(&memcg_oom_lock);
if (need_to_kill) {
finish_wait(&memcg_oom_waitq, &owait.wait);
@@ -1884,11 +1884,11 @@ bool mem_cgroup_handle_oom(struct mem_cg
schedule();
finish_wait(&memcg_oom_waitq, &owait.wait);
}
- mutex_lock(&memcg_oom_mutex);
+ spin_lock(&memcg_oom_lock);
if (locked)
mem_cgroup_oom_unlock(mem);
memcg_wakeup_oom(mem);
- mutex_unlock(&memcg_oom_mutex);
+ spin_unlock(&memcg_oom_lock);
mem_cgroup_unmark_under_oom(mem);
@@ -4503,7 +4503,7 @@ static int mem_cgroup_oom_register_event
if (!event)
return -ENOMEM;
- mutex_lock(&memcg_oom_mutex);
+ spin_lock(&memcg_oom_lock);
event->eventfd = eventfd;
list_add(&event->list, &memcg->oom_notify);
@@ -4511,7 +4511,7 @@ static int mem_cgroup_oom_register_event
/* already in OOM ? */
if (atomic_read(&memcg->under_oom))
eventfd_signal(eventfd, 1);
- mutex_unlock(&memcg_oom_mutex);
+ spin_unlock(&memcg_oom_lock);
return 0;
}
@@ -4525,7 +4525,7 @@ static void mem_cgroup_oom_unregister_ev
BUG_ON(type != _OOM_TYPE);
- mutex_lock(&memcg_oom_mutex);
+ spin_lock(&memcg_oom_lock);
list_for_each_entry_safe(ev, tmp, &mem->oom_notify, list) {
if (ev->eventfd == eventfd) {
@@ -4534,7 +4534,7 @@ static void mem_cgroup_oom_unregister_ev
}
}
- mutex_unlock(&memcg_oom_mutex);
+ spin_unlock(&memcg_oom_lock);
}
static int mem_cgroup_oom_control_read(struct cgroup *cgrp,
_
Patches currently in -mm which might be from mhocko@xxxxxxx are
linux-next.patch
mm-remove-the-leftovers-of-noswapaccount.patch
mm-thp-minor-lock-simplification-in-__khugepaged_exit.patch
mm-preallocate-page-before-lock_page-at-filemap-cow.patch
um-clean-up-vm-flagsh.patch
memcg-export-memory-cgroups-swappiness-with-mem_cgroup_swappiness.patch
memcg-consolidates-memory-cgroup-lru-stat-functions.patch
memcg-consolidates-memory-cgroup-lru-stat-functions-fix.patch
memcg-do-not-expose-uninitialized-mem_cgroup_per_node-to-world.patch
memcg-make-oom_lock-0-and-1-based-rather-than-counter.patch
memcg-change-memcg_oom_mutex-to-spinlock.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-fix-2.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-cpusets-initialize-spread-rotor-lazily.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-cpusets-initialize-spread-rotor-lazily-fix.patch
fs-execc-use-build_bug_on-for-vm_stack_flags-vm_stack_incomplete_setup.patch
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