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memcg: oom kill disable and oom status
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This adds a feature to disable oom-killer for memcg, if disabled, of
course, tasks under memcg will stop.

But now, we have oom-notifier for memcg.  And the world around memcg is
not under out-of-memory.  memcg's out-of-memory just shows memcg hits
limit.  Then, administrator or management daemon can recover the situation
by

	- kill some process
	- enlarge limit, add more swap.
	- migrate some tasks
	- remove file cache on tmps (difficult ?)

Unlike oom-killer, you can take enough information before killing tasks.
(by gcore, or, ps etc.)

[[email protected]: coding-style fixes]
Signed-off-by: KAMEZAWA Hiroyuki <[email protected]>
Cc: Daisuke Nishimura <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Daisuke Nishimura <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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hkamezawa authored and torvalds committed May 27, 2010
1 parent 9490ff2 commit 3c11ecf
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23 changes: 23 additions & 0 deletions Documentation/cgroups/memory.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -493,6 +493,8 @@ It's applicable for root and non-root cgroup.

10. OOM Control

memory.oom_control file is for OOM notification and other controls.

Memory controler implements oom notifier using cgroup notification
API (See cgroups.txt). It allows to register multiple oom notification
delivery and gets notification when oom happens.
Expand All @@ -505,6 +507,27 @@ To register a notifier, application need:
Application will be notifier through eventfd when oom happens.
OOM notification doesn't work for root cgroup.

You can disable oom-killer by writing "1" to memory.oom_control file.
As.
#echo 1 > memory.oom_control

This operation is only allowed to the top cgroup of subhierarchy.
If oom-killer is disabled, tasks under cgroup will hang/sleep
in memcg's oom-waitq when they request accountable memory.

For running them, you have to relax the memcg's oom sitaution by
* enlarge limit or reduce usage.
To reduce usage,
* kill some tasks.
* move some tasks to other group with account migration.
* remove some files (on tmpfs?)

Then, stopped tasks will work again.

At reading, current status of OOM is shown.
oom_kill_disable 0 or 1 (if 1, oom-killer is disabled)
under_oom 0 or 1 (if 1, the memcg is under OOM,tasks may
be stopped.)

11. TODO

Expand Down
113 changes: 94 additions & 19 deletions mm/memcontrol.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -214,6 +214,8 @@ struct mem_cgroup {
atomic_t refcnt;

unsigned int swappiness;
/* OOM-Killer disable */
int oom_kill_disable;

/* set when res.limit == memsw.limit */
bool memsw_is_minimum;
Expand All @@ -235,7 +237,6 @@ struct mem_cgroup {
* mem_cgroup ? And what type of charges should we move ?
*/
unsigned long move_charge_at_immigrate;

/*
* percpu counter.
*/
Expand Down Expand Up @@ -1342,20 +1343,26 @@ static void memcg_wakeup_oom(struct mem_cgroup *mem)
__wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, mem);
}

static void memcg_oom_recover(struct mem_cgroup *mem)
{
if (mem->oom_kill_disable && atomic_read(&mem->oom_lock))
memcg_wakeup_oom(mem);
}

/*
* try to call OOM killer. returns false if we should exit memory-reclaim loop.
*/
bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
{
struct oom_wait_info owait;
bool locked;
bool locked, need_to_kill;

owait.mem = mem;
owait.wait.flags = 0;
owait.wait.func = memcg_oom_wake_function;
owait.wait.private = current;
INIT_LIST_HEAD(&owait.wait.task_list);

need_to_kill = true;
/* At first, try to OOM lock hierarchy under mem.*/
mutex_lock(&memcg_oom_mutex);
locked = mem_cgroup_oom_lock(mem);
Expand All @@ -1364,15 +1371,17 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
* accounting. So, UNINTERRUPTIBLE is appropriate. But SIGKILL
* under OOM is always welcomed, use TASK_KILLABLE here.
*/
if (!locked)
prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
else
prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
if (!locked || mem->oom_kill_disable)
need_to_kill = false;
if (locked)
mem_cgroup_oom_notify(mem);
mutex_unlock(&memcg_oom_mutex);

if (locked)
if (need_to_kill) {
finish_wait(&memcg_oom_waitq, &owait.wait);
mem_cgroup_out_of_memory(mem, mask);
else {
} else {
schedule();
finish_wait(&memcg_oom_waitq, &owait.wait);
}
Expand Down Expand Up @@ -2162,15 +2171,6 @@ __do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype)
/* If swapout, usage of swap doesn't decrease */
if (!do_swap_account || ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
uncharge_memsw = false;
/*
* do_batch > 0 when unmapping pages or inode invalidate/truncate.
* In those cases, all pages freed continously can be expected to be in
* the same cgroup and we have chance to coalesce uncharges.
* But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
* because we want to do uncharge as soon as possible.
*/
if (!current->memcg_batch.do_batch || test_thread_flag(TIF_MEMDIE))
goto direct_uncharge;

batch = &current->memcg_batch;
/*
Expand All @@ -2180,6 +2180,17 @@ __do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype)
*/
if (!batch->memcg)
batch->memcg = mem;
/*
* do_batch > 0 when unmapping pages or inode invalidate/truncate.
* In those cases, all pages freed continously can be expected to be in
* the same cgroup and we have chance to coalesce uncharges.
* But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
* because we want to do uncharge as soon as possible.
*/

if (!batch->do_batch || test_thread_flag(TIF_MEMDIE))
goto direct_uncharge;

/*
* In typical case, batch->memcg == mem. This means we can
* merge a series of uncharges to an uncharge of res_counter.
Expand All @@ -2196,6 +2207,8 @@ __do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype)
res_counter_uncharge(&mem->res, PAGE_SIZE);
if (uncharge_memsw)
res_counter_uncharge(&mem->memsw, PAGE_SIZE);
if (unlikely(batch->memcg != mem))
memcg_oom_recover(mem);
return;
}

Expand Down Expand Up @@ -2332,6 +2345,7 @@ void mem_cgroup_uncharge_end(void)
res_counter_uncharge(&batch->memcg->res, batch->bytes);
if (batch->memsw_bytes)
res_counter_uncharge(&batch->memcg->memsw, batch->memsw_bytes);
memcg_oom_recover(batch->memcg);
/* forget this pointer (for sanity check) */
batch->memcg = NULL;
}
Expand Down Expand Up @@ -2568,10 +2582,11 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
unsigned long long val)
{
int retry_count;
u64 memswlimit;
u64 memswlimit, memlimit;
int ret = 0;
int children = mem_cgroup_count_children(memcg);
u64 curusage, oldusage;
int enlarge;

/*
* For keeping hierarchical_reclaim simple, how long we should retry
Expand All @@ -2582,6 +2597,7 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,

oldusage = res_counter_read_u64(&memcg->res, RES_USAGE);

enlarge = 0;
while (retry_count) {
if (signal_pending(current)) {
ret = -EINTR;
Expand All @@ -2599,6 +2615,11 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
mutex_unlock(&set_limit_mutex);
break;
}

memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
if (memlimit < val)
enlarge = 1;

ret = res_counter_set_limit(&memcg->res, val);
if (!ret) {
if (memswlimit == val)
Expand All @@ -2620,6 +2641,8 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
else
oldusage = curusage;
}
if (!ret && enlarge)
memcg_oom_recover(memcg);

return ret;
}
Expand All @@ -2628,9 +2651,10 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
unsigned long long val)
{
int retry_count;
u64 memlimit, oldusage, curusage;
u64 memlimit, memswlimit, oldusage, curusage;
int children = mem_cgroup_count_children(memcg);
int ret = -EBUSY;
int enlarge = 0;

/* see mem_cgroup_resize_res_limit */
retry_count = children * MEM_CGROUP_RECLAIM_RETRIES;
Expand All @@ -2652,6 +2676,9 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
mutex_unlock(&set_limit_mutex);
break;
}
memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
if (memswlimit < val)
enlarge = 1;
ret = res_counter_set_limit(&memcg->memsw, val);
if (!ret) {
if (memlimit == val)
Expand All @@ -2674,6 +2701,8 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
else
oldusage = curusage;
}
if (!ret && enlarge)
memcg_oom_recover(memcg);
return ret;
}

Expand Down Expand Up @@ -2865,6 +2894,7 @@ static int mem_cgroup_force_empty(struct mem_cgroup *mem, bool free_all)
if (ret)
break;
}
memcg_oom_recover(mem);
/* it seems parent cgroup doesn't have enough mem */
if (ret == -ENOMEM)
goto try_to_free;
Expand Down Expand Up @@ -3645,6 +3675,46 @@ static int mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
return 0;
}

static int mem_cgroup_oom_control_read(struct cgroup *cgrp,
struct cftype *cft, struct cgroup_map_cb *cb)
{
struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);

cb->fill(cb, "oom_kill_disable", mem->oom_kill_disable);

if (atomic_read(&mem->oom_lock))
cb->fill(cb, "under_oom", 1);
else
cb->fill(cb, "under_oom", 0);
return 0;
}

/*
*/
static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
struct cftype *cft, u64 val)
{
struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
struct mem_cgroup *parent;

/* cannot set to root cgroup and only 0 and 1 are allowed */
if (!cgrp->parent || !((val == 0) || (val == 1)))
return -EINVAL;

parent = mem_cgroup_from_cont(cgrp->parent);

cgroup_lock();
/* oom-kill-disable is a flag for subhierarchy. */
if ((parent->use_hierarchy) ||
(mem->use_hierarchy && !list_empty(&cgrp->children))) {
cgroup_unlock();
return -EINVAL;
}
mem->oom_kill_disable = val;
cgroup_unlock();
return 0;
}

static struct cftype mem_cgroup_files[] = {
{
.name = "usage_in_bytes",
Expand Down Expand Up @@ -3702,6 +3772,8 @@ static struct cftype mem_cgroup_files[] = {
},
{
.name = "oom_control",
.read_map = mem_cgroup_oom_control_read,
.write_u64 = mem_cgroup_oom_control_write,
.register_event = mem_cgroup_oom_register_event,
.unregister_event = mem_cgroup_oom_unregister_event,
.private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
Expand Down Expand Up @@ -3943,6 +4015,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
} else {
parent = mem_cgroup_from_cont(cont->parent);
mem->use_hierarchy = parent->use_hierarchy;
mem->oom_kill_disable = parent->oom_kill_disable;
}

if (parent && parent->use_hierarchy) {
Expand Down Expand Up @@ -4215,6 +4288,7 @@ static void mem_cgroup_clear_mc(void)
if (mc.precharge) {
__mem_cgroup_cancel_charge(mc.to, mc.precharge);
mc.precharge = 0;
memcg_oom_recover(mc.to);
}
/*
* we didn't uncharge from mc.from at mem_cgroup_move_account(), so
Expand All @@ -4223,6 +4297,7 @@ static void mem_cgroup_clear_mc(void)
if (mc.moved_charge) {
__mem_cgroup_cancel_charge(mc.from, mc.moved_charge);
mc.moved_charge = 0;
memcg_oom_recover(mc.from);
}
/* we must fixup refcnts and charges */
if (mc.moved_swap) {
Expand Down

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