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Subject[PATCH RFC v0 3/3] memcg: implement memory thresholds
Date
It allows to register multiple memory thresholds and gets notifications
when it crosses.

To register a threshold application need:
- create an eventfd;
- open file memory.usage_in_bytes of a cgroup
- write string "<event_fd> <memory.usage_in_bytes> <threshold>" to
cgroup.event_control.

Application will be notified through eventfd when memory usage crosses
threshold in any direction.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
---
mm/memcontrol.c | 149 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 149 insertions(+), 0 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f99f599..af1af0b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6,6 +6,10 @@
* Copyright 2007 OpenVZ SWsoft Inc
* Author: Pavel Emelianov <xemul@openvz.org>
*
+ * Memory thresholds
+ * Copyright (C) 2009 Nokia Corporation
+ * Author: Kirill A. Shutemov
+ *
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
@@ -38,6 +42,7 @@
#include <linux/vmalloc.h>
#include <linux/mm_inline.h>
#include <linux/page_cgroup.h>
+#include <linux/eventfd.h>
#include "internal.h"

#include <asm/uaccess.h>
@@ -174,6 +179,12 @@ struct mem_cgroup_tree {

static struct mem_cgroup_tree soft_limit_tree __read_mostly;

+struct mem_cgroup_threshold {
+ struct list_head list;
+ struct eventfd_ctx *eventfd;
+ u64 threshold;
+};
+
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
@@ -225,6 +236,9 @@ struct mem_cgroup {
/* set when res.limit == memsw.limit */
bool memsw_is_minimum;

+ struct list_head thresholds;
+ struct mem_cgroup_threshold *current_threshold;
+
/*
* statistics. This must be placed at the end of memcg.
*/
@@ -2839,12 +2853,119 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
return 0;
}

+static inline void mem_cgroup_set_thresholds(struct res_counter *counter,
+ u64 above, u64 below)
+{
+ BUG_ON(res_counter_set_thresholds(counter, above, below));
+}
+
+static void mem_cgroup_threshold(struct res_counter *counter, u64 usage,
+ u64 threshold)
+{
+ struct mem_cgroup *memcg = container_of(counter,
+ struct mem_cgroup,res);
+ struct mem_cgroup_threshold *above, *below;
+
+ above = below = memcg->current_threshold;
+
+ if (threshold <= usage) {
+ list_for_each_entry_continue(above, &memcg->thresholds,
+ list) {
+ if (above->threshold > usage)
+ break;
+ below = above;
+ eventfd_signal(below->eventfd, 1);
+ }
+ } else {
+ list_for_each_entry_continue_reverse(below,
+ &memcg->thresholds, list) {
+ eventfd_signal(above->eventfd, 1);
+ if (below->threshold <= usage)
+ break;
+ above = below;
+ }
+ }
+
+ mem_cgroup_set_thresholds(&memcg->res, above->threshold,
+ below->threshold);
+ memcg->current_threshold = below;
+}
+
+static void mem_cgroup_invalidate_thresholds(struct cgroup *cgrp)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+ struct mem_cgroup_threshold *tmp, *prev = NULL;
+ u64 usage = memcg->res.usage;
+
+ list_for_each_entry(tmp, &memcg->thresholds, list) {
+ if (tmp->threshold > usage) {
+ BUG_ON(!prev);
+ memcg->current_threshold = prev;
+ break;
+ }
+ prev = tmp;
+ }
+
+ mem_cgroup_set_thresholds(&memcg->res, tmp->threshold,
+ prev->threshold);
+}
+
+static int mem_cgroup_register_event(struct cgroup *cgrp, struct cftype *cft,
+ struct eventfd_ctx *eventfd, const char *args)
+{
+ u64 threshold;
+ struct mem_cgroup_threshold *new, *tmp;
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+ int ret;
+
+ /* TODO: Root cgroup is a special case */
+ if (mem_cgroup_is_root(memcg))
+ return -ENOSYS;
+
+ ret = res_counter_memparse_write_strategy(args, &threshold);
+ if (ret)
+ return ret;
+
+ new = kmalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ return -ENOMEM;
+ INIT_LIST_HEAD(&new->list);
+ new->eventfd = eventfd;
+ new->threshold = threshold;
+
+ list_for_each_entry(tmp, &memcg->thresholds, list)
+ if (new->threshold < tmp->threshold) {
+ list_add_tail(&new->list, &tmp->list);
+ break;
+ }
+ mem_cgroup_invalidate_thresholds(cgrp);
+
+ return 0;
+}
+
+static int mem_cgroup_unregister_event(struct cgroup *cgrp, struct cftype *cft,
+ struct eventfd_ctx *eventfd)
+{
+ struct mem_cgroup_threshold *threshold, *tmp;
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+
+ list_for_each_entry_safe(threshold, tmp, &memcg->thresholds, list)
+ if (threshold->eventfd == eventfd) {
+ list_del(&threshold->list);
+ kfree(threshold);
+ }
+ mem_cgroup_invalidate_thresholds(cgrp);
+
+ 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,
},
{
.name = "max_usage_in_bytes",
@@ -3080,6 +3201,32 @@ static int mem_cgroup_soft_limit_tree_init(void)
return 0;
}

+static int mem_cgroup_thresholds_init(struct mem_cgroup *mem)
+{
+ struct mem_cgroup_threshold *new;
+
+ mem->res.threshold_notifier = mem_cgroup_threshold;
+ INIT_LIST_HEAD(&mem->thresholds);
+
+ new = kmalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ return -ENOMEM;
+ INIT_LIST_HEAD(&new->list);
+ new->threshold = 0ULL;
+ list_add(&new->list, &mem->thresholds);
+
+ mem->current_threshold = new;
+
+ new = kmalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ return -ENOMEM;
+ INIT_LIST_HEAD(&new->list);
+ new->threshold = RESOURCE_MAX;
+ list_add_tail(&new->list, &mem->thresholds);
+
+ return 0;
+}
+
static struct cgroup_subsys_state * __ref
mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
{
@@ -3125,6 +3272,8 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
mem->last_scanned_child = 0;
spin_lock_init(&mem->reclaim_param_lock);

+ mem_cgroup_thresholds_init(mem);
+
if (parent)
mem->swappiness = get_swappiness(parent);
atomic_set(&mem->refcnt, 1);
--
1.6.5.3


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