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Date: Thu, 11 Mar 2010 16:47:00 +0200
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 2/3] memcg: oom notifier
On Thu, Mar 11, 2010 at 9:57 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
> Considering containers or other resource management softwares in userland,
> event notification of OOM in memcg should be implemented.
> Now, memcg has "threshold" notifier which uses eventfd, we can make
> use of it for oom notification.
>
> This patch adds oom notification eventfd callback for memcg. The usage
> is very similar to threshold notifier, but control file is
> memory.oom_control and no arguments other than eventfd is required.
>
> % cgroup_event_notifier /cgroup/A/memory.oom_control dummy
> (About cgroup_event_notifier, see Documentation/cgroup/)
>
> TODO:
> - add a knob to disable oom-kill under a memcg.
> - add read/write function to oom_control
>
> Changelog: 20100309
> - splitted from threshold functions. use list rather than array.
> - moved all to inside of mutex.
> Changelog: 20100304
> - renewed implemenation.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Looks great! Two remarks below.
Reviewed-by: Kirill A. Shutemov <kirill@...temov.name>
> ---
> Documentation/cgroups/memory.txt | 20 +++++++
> mm/memcontrol.c | 105 ++++++++++++++++++++++++++++++++++++---
> 2 files changed, 116 insertions(+), 9 deletions(-)
>
> Index: mmotm-2.6.34-Mar9/mm/memcontrol.c
> ===================================================================
> --- mmotm-2.6.34-Mar9.orig/mm/memcontrol.c
> +++ mmotm-2.6.34-Mar9/mm/memcontrol.c
> @@ -149,6 +149,7 @@ struct mem_cgroup_threshold {
> u64 threshold;
> };
>
> +/* For threshold */
> struct mem_cgroup_threshold_ary {
> /* An array index points to threshold just below usage. */
> atomic_t current_threshold;
> @@ -157,8 +158,14 @@ struct mem_cgroup_threshold_ary {
> /* Array of thresholds */
> struct mem_cgroup_threshold entries[0];
> };
> +/* for OOM */
> +struct mem_cgroup_eventfd_list {
> + struct list_head list;
> + struct eventfd_ctx *eventfd;
> +};
>
> static void mem_cgroup_threshold(struct mem_cgroup *mem);
> +static void mem_cgroup_oom_notify(struct mem_cgroup *mem);
>
> /*
> * The memory controller data structure. The memory controller controls both
> @@ -220,6 +227,9 @@ struct mem_cgroup {
> /* thresholds for mem+swap usage. RCU-protected */
> struct mem_cgroup_threshold_ary *memsw_thresholds;
>
> + /* For oom notifier event fd */
> + struct list_head oom_notify;
> +
> /*
> * Should we move charges of a task when a task is moved into this
> * mem_cgroup ? And what type of charges should we move ?
> @@ -282,9 +292,12 @@ enum charge_type {
> /* for encoding cft->private value on file */
> #define _MEM (0)
> #define _MEMSWAP (1)
> +#define _OOM_TYPE (2)
> #define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
> #define MEMFILE_TYPE(val) (((val) >> 16) & 0xffff)
> #define MEMFILE_ATTR(val) ((val) & 0xffff)
> +/* Used for OOM nofiier */
> +#define OOM_CONTROL (0)
>
> /*
> * Reclaim flags for mem_cgroup_hierarchical_reclaim
> @@ -1351,6 +1364,8 @@ bool mem_cgroup_handle_oom(struct mem_cg
> */
> if (!locked)
> prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
> + else
> + mem_cgroup_oom_notify(mem);
> mutex_unlock(&memcg_oom_mutex);
>
> if (locked)
> @@ -3398,8 +3413,22 @@ static int compare_thresholds(const void
> return _a->threshold - _b->threshold;
> }
>
> -static int mem_cgroup_register_event(struct cgroup *cgrp, struct cftype *cft,
> - struct eventfd_ctx *eventfd, const char *args)
> +static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem, void *data)
> +{
> + struct mem_cgroup_eventfd_list *ev;
> +
> + list_for_each_entry(ev, &mem->oom_notify, list)
> + eventfd_signal(ev->eventfd, 1);
> + return 0;
> +}
> +
> +static void mem_cgroup_oom_notify(struct mem_cgroup *mem)
> +{
> + mem_cgroup_walk_tree(mem, NULL, mem_cgroup_oom_notify_cb);
> +}
> +
> +static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
> + struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
> @@ -3483,8 +3512,8 @@ unlock:
> return ret;
> }
>
> -static int mem_cgroup_unregister_event(struct cgroup *cgrp, struct cftype *cft,
> - struct eventfd_ctx *eventfd)
> +static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
> + struct cftype *cft, struct eventfd_ctx *eventfd)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
> @@ -3568,13 +3597,66 @@ unlock:
> return ret;
> }
>
> +static int mem_cgroup_oom_register_event(struct cgroup *cgrp,
> + struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
> +{
> + struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> + struct mem_cgroup_eventfd_list *event;
> + int type = MEMFILE_TYPE(cft->private);
> + int ret = -ENOMEM;
> +
> + BUG_ON(type != _OOM_TYPE);
> +
> + mutex_lock(&memcg_oom_mutex);
> +
> + /* Allocate memory for new array of thresholds */
Irrelevant comment?
> + event = kmalloc(sizeof(*event), GFP_KERNEL);
> + if (!event)
> + goto unlock;
> + /* Add new threshold */
Ditto.
> + event->eventfd = eventfd;
> + list_add(&event->list, &memcg->oom_notify);
> +
> + /* already in OOM ? */
> + if (atomic_read(&memcg->oom_lock))
> + eventfd_signal(eventfd, 1);
> + ret = 0;
> +unlock:
> + mutex_unlock(&memcg_oom_mutex);
> +
> + return ret;
> +}
> +
> +static int mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
> + struct cftype *cft, struct eventfd_ctx *eventfd)
> +{
> + struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
> + struct mem_cgroup_eventfd_list *ev, *tmp;
> + int type = MEMFILE_TYPE(cft->private);
> +
> + BUG_ON(type != _OOM_TYPE);
> +
> + mutex_lock(&memcg_oom_mutex);
> +
> + list_for_each_entry_safe(ev, tmp, &mem->oom_notify, list) {
> + if (ev->eventfd == eventfd) {
> + list_del(&ev->list);
> + kfree(ev);
> + }
> + }
> +
> + mutex_unlock(&memcg_oom_mutex);
> +
> + return 0;
> +}
> +
> static struct cftype mem_cgroup_files[] = {
> {
> .name = "usage_in_bytes",
> .private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
> .read_u64 = mem_cgroup_read,
> - .register_event = mem_cgroup_register_event,
> - .unregister_event = mem_cgroup_unregister_event,
> + .register_event = mem_cgroup_usage_register_event,
> + .unregister_event = mem_cgroup_usage_unregister_event,
> },
> {
> .name = "max_usage_in_bytes",
> @@ -3623,6 +3705,12 @@ static struct cftype mem_cgroup_files[]
> .read_u64 = mem_cgroup_move_charge_read,
> .write_u64 = mem_cgroup_move_charge_write,
> },
> + {
> + .name = "oom_control",
> + .register_event = mem_cgroup_oom_register_event,
> + .unregister_event = mem_cgroup_oom_unregister_event,
> + .private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
> + },
> };
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> @@ -3631,8 +3719,8 @@ static struct cftype memsw_cgroup_files[
> .name = "memsw.usage_in_bytes",
> .private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
> .read_u64 = mem_cgroup_read,
> - .register_event = mem_cgroup_register_event,
> - .unregister_event = mem_cgroup_unregister_event,
> + .register_event = mem_cgroup_usage_register_event,
> + .unregister_event = mem_cgroup_usage_unregister_event,
> },
> {
> .name = "memsw.max_usage_in_bytes",
> @@ -3876,6 +3964,7 @@ mem_cgroup_create(struct cgroup_subsys *
> }
> mem->last_scanned_child = 0;
> spin_lock_init(&mem->reclaim_param_lock);
> + INIT_LIST_HEAD(&mem->oom_notify);
>
> if (parent)
> mem->swappiness = get_swappiness(parent);
> Index: mmotm-2.6.34-Mar9/Documentation/cgroups/memory.txt
> ===================================================================
> --- mmotm-2.6.34-Mar9.orig/Documentation/cgroups/memory.txt
> +++ mmotm-2.6.34-Mar9/Documentation/cgroups/memory.txt
> @@ -184,6 +184,9 @@ limits on the root cgroup.
>
> Note2: When panic_on_oom is set to "2", the whole system will panic.
>
> +When oom event notifier is registered, event will be delivered.
> +(See oom_control section)
> +
> 2. Locking
>
> The memory controller uses the following hierarchy
> @@ -488,7 +491,22 @@ threshold in any direction.
>
> It's applicable for root and non-root cgroup.
>
> -10. TODO
> +10. OOM Control
> +
> +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.
> +
> +To register a notifier, application need:
> + - create an eventfd using eventfd(2)
> + - open memory.oom_control file
> + - write string like "<event_fd> <memory.oom_control>" to cgroup.event_control
> +
> +Application will be notifier through eventfd when oom happens.
> +OOM notification doesn't work for root cgroup.
> +
> +
> +11. TODO
>
> 1. Add support for accounting huge pages (as a separate controller)
> 2. Make per-cgroup scanner reclaim not-shared pages first
>
>
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