[PATCH RFC v2 4/4] memcg: implement memory thresholds
KAMEZAWA Hiroyuki
kamezawa.hiroyu at jp.fujitsu.com
Mon Dec 14 17:58:50 PST 2009
On Sat, 12 Dec 2009 00:59:19 +0200
"Kirill A. Shutemov" <kirill at shutemov.name> wrote:
> It allows to register multiple memory and memsw thresholds and gets
> notifications when it crosses.
>
> To register a threshold application need:
> - create an eventfd;
> - open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
> - write string like "<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.
>
> It's applicable for root and non-root cgroup.
>
> It uses stats to track memory usage, simmilar to soft limits. It checks
> if we need to send event to userspace on every 100 page in/out. I guess
> it's good compromise between performance and accuracy of thresholds.
>
> Signed-off-by: Kirill A. Shutemov <kirill at shutemov.name>
> ---
> mm/memcontrol.c | 263 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 263 insertions(+), 0 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index c6081cc..5ba2140 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6,6 +6,10 @@
> * Copyright 2007 OpenVZ SWsoft Inc
> * Author: Pavel Emelianov <xemul at 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>
> @@ -56,6 +61,7 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
>
> static DEFINE_MUTEX(memcg_tasklist); /* can be hold under cgroup_mutex */
> #define SOFTLIMIT_EVENTS_THRESH (1000)
> +#define THRESHOLDS_EVENTS_THRESH (100)
>
> /*
> * Statistics for memory cgroup.
> @@ -72,6 +78,8 @@ enum mem_cgroup_stat_index {
> MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
> MEM_CGROUP_STAT_SOFTLIMIT, /* decrements on each page in/out.
> used by soft limit implementation */
> + MEM_CGROUP_STAT_THRESHOLDS, /* decrements on each page in/out.
> + used by threshold implementation */
>
> MEM_CGROUP_STAT_NSTATS,
> };
> @@ -182,6 +190,15 @@ 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;
> +};
> +
> +static bool mem_cgroup_threshold_check(struct mem_cgroup* mem);
> +static void mem_cgroup_threshold(struct mem_cgroup* mem, bool swap);
> +
> /*
> * The memory controller data structure. The memory controller controls both
> * page cache and RSS per cgroup. We would eventually like to provide
> @@ -233,6 +250,19 @@ struct mem_cgroup {
> /* set when res.limit == memsw.limit */
> bool memsw_is_minimum;
>
> + /* protect lists of thresholds*/
> + spinlock_t thresholds_lock;
> +
> + /* thresholds for memory usage */
> + struct list_head thresholds;
> + struct mem_cgroup_threshold *below_threshold;
> + struct mem_cgroup_threshold *above_threshold;
> +
> + /* thresholds for mem+swap usage */
> + struct list_head memsw_thresholds;
> + struct mem_cgroup_threshold *memsw_below_threshold;
> + struct mem_cgroup_threshold *memsw_above_threshold;
> +
> /*
> * statistics. This must be placed at the end of memcg.
> */
> @@ -519,6 +549,8 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
> __mem_cgroup_stat_add_safe(cpustat,
> MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
> __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT, -1);
> + __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_THRESHOLDS, -1);
> +
> put_cpu();
> }
>
> @@ -1363,6 +1395,11 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
> if (mem_cgroup_soft_limit_check(mem))
> mem_cgroup_update_tree(mem, page);
> done:
> + if (mem_cgroup_threshold_check(mem)) {
> + mem_cgroup_threshold(mem, false);
> + if (do_swap_account)
> + mem_cgroup_threshold(mem, true);
> + }
> return 0;
> nomem:
> css_put(&mem->css);
> @@ -1906,6 +1943,11 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
>
> if (mem_cgroup_soft_limit_check(mem))
> mem_cgroup_update_tree(mem, page);
> + if (mem_cgroup_threshold_check(mem)) {
> + mem_cgroup_threshold(mem, false);
> + if (do_swap_account)
> + mem_cgroup_threshold(mem, true);
> + }
> /* at swapout, this memcg will be accessed to record to swap */
> if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
> css_put(&mem->css);
> @@ -2860,11 +2902,181 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
> }
>
>
> +static bool mem_cgroup_threshold_check(struct mem_cgroup *mem)
> +{
> + bool ret = false;
> + int cpu;
> + s64 val;
> + struct mem_cgroup_stat_cpu *cpustat;
> +
> + cpu = get_cpu();
> + cpustat = &mem->stat.cpustat[cpu];
> + val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_THRESHOLDS);
> + if (unlikely(val < 0)) {
> + __mem_cgroup_stat_set(cpustat, MEM_CGROUP_STAT_THRESHOLDS,
> + THRESHOLDS_EVENTS_THRESH);
> + ret = true;
> + }
> + put_cpu();
> + return ret;
> +}
> +
Hmm. please check
if (likely(list_empty(&mem->thesholds) &&
list_empty(&mem->memsw_thresholds)))
return;
or adds a flag as mem->no_threshold_check to skip this routine quickly.
_OR_
I personally don't like to have 2 counters to catch events.
How about this ?
adds
struct mem_cgroup {
atomic_t event_counter; // this is incremented per 32
page-in/out
atomic_t last_softlimit_check;
atomic_t last_thresh_check;
};
static bool mem_cgroup_threshold_check(struct mem_cgroup *mem)
{
decrement percpu event counter.
if (percpu counter reaches 0) {
if (atomic_dec_and_test(&mem->check_thresh) {
check threashold.
reset counter.
}
if (atomic_dec_and_test(&memc->check_softlimit) {
update softlimit tree.
reset counter.
}
reset percpu counter.
}
}
Then, you can have a counter like system-wide event counter.
> +static void mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
> +{
> + struct mem_cgroup_threshold **below, **above;
> + struct list_head *thresholds;
> + u64 usage = mem_cgroup_usage(memcg, swap);
> +
> + if (!swap) {
> + thresholds = &memcg->thresholds;
> + above = &memcg->above_threshold;
> + below = &memcg->below_threshold;
> + } else {
> + thresholds = &memcg->memsw_thresholds;
> + above = &memcg->memsw_above_threshold;
> + below = &memcg->memsw_below_threshold;
> + }
> +
> + spin_lock(&memcg->thresholds_lock);
> + if ((*above)->threshold <= usage) {
> + *below = *above;
> + list_for_each_entry_continue((*above), thresholds, list) {
> + eventfd_signal((*below)->eventfd, 1);
> + if ((*above)->threshold > usage)
> + break;
> + *below = *above;
> + }
> + } else if ((*below)->threshold > usage) {
> + *above = *below;
> + list_for_each_entry_continue_reverse((*below), thresholds,
> + list) {
> + eventfd_signal((*above)->eventfd, 1);
> + if ((*below)->threshold <= usage)
> + break;
> + *above = *below;
> + }
> + }
> + spin_unlock(&memcg->thresholds_lock);
> +}
Could you adds comment on above check ?
And do we need *spin_lock* here ? Can't you use RCU list walk ?
If you use have to use spinlock here, this is a system-wide spinlock,
threshold as "100" is too small, I think.
Even if you can't use spinlock, please use mutex. (with checking gfp_mask).
Thanks,
-Kame
> +
> +static void mem_cgroup_invalidate_thresholds(struct mem_cgroup *memcg,
> + bool swap)
> +{
> + struct list_head *thresholds;
> + struct mem_cgroup_threshold **below, **above;
> + u64 usage = mem_cgroup_usage(memcg, swap);
> +
> + if (!swap) {
> + thresholds = &memcg->thresholds;
> + above = &memcg->above_threshold;
> + below = &memcg->below_threshold;
> + } else {
> + thresholds = &memcg->memsw_thresholds;
> + above = &memcg->memsw_above_threshold;
> + below = &memcg->memsw_below_threshold;
> + }
> +
> + *below = NULL;
> + list_for_each_entry((*above), thresholds, list) {
> + if ((*above)->threshold > usage) {
> + BUG_ON(!*below);
> + break;
> + }
> + *below = *above;
> + }
> +}
> +
> +static inline struct mem_cgroup_threshold *mem_cgroup_threshold_alloc(void)
> +{
> + struct mem_cgroup_threshold *new;
> +
> + new = kmalloc(sizeof(*new), GFP_KERNEL);
> + if (!new)
> + return NULL;
> + INIT_LIST_HEAD(&new->list);
> +
> + return new;
> +}
> +
> +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);
> + struct list_head *thresholds;
> + int type = MEMFILE_TYPE(cft->private);
> + int ret;
> +
> + ret = res_counter_memparse_write_strategy(args, &threshold);
> + if (ret)
> + return ret;
> +
> + new = mem_cgroup_threshold_alloc();
> + if (!new)
> + return -ENOMEM;
> + new->eventfd = eventfd;
> + new->threshold = threshold;
> +
> + if (type == _MEM)
> + thresholds = &memcg->thresholds;
> + else if (type == _MEMSWAP)
> + thresholds = &memcg->memsw_thresholds;
> + else
> + BUG();
> +
> + /* Check if a threshold crossed before adding a new one */
> + mem_cgroup_threshold(memcg, type == _MEMSWAP);
> +
> + spin_lock(&memcg->thresholds_lock);
> + list_for_each_entry(tmp, thresholds, list)
> + if (new->threshold < tmp->threshold) {
> + list_add_tail(&new->list, &tmp->list);
> + break;
> + }
> + mem_cgroup_invalidate_thresholds(memcg, type == _MEMSWAP);
> + spin_unlock(&memcg->thresholds_lock);
> +
> + 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);
> + struct list_head *thresholds;
> + int type = MEMFILE_TYPE(cft->private);
> +
> + if (type == _MEM)
> + thresholds = &memcg->thresholds;
> + else if (type == _MEMSWAP)
> + thresholds = &memcg->memsw_thresholds;
> + else
> + BUG();
> +
> + /* Check if a threshold crossed before adding a new one */
> + mem_cgroup_threshold(memcg, type == _MEMSWAP);
> +
> + spin_lock(&memcg->thresholds_lock);
> + list_for_each_entry_safe(threshold, tmp, thresholds, list)
> + if (threshold->eventfd == eventfd) {
> + list_del(&threshold->list);
> + kfree(threshold);
> + }
> + mem_cgroup_invalidate_thresholds(memcg, type == _MEMSWAP);
> + spin_unlock(&memcg->thresholds_lock);
> +
> + 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",
> @@ -2916,6 +3128,8 @@ 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,
> },
> {
> .name = "memsw.max_usage_in_bytes",
> @@ -2990,6 +3204,48 @@ static void free_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
> kfree(mem->info.nodeinfo[node]);
> }
>
> +static int mem_cgroup_thresholds_init(struct mem_cgroup *mem)
> +{
> + INIT_LIST_HEAD(&mem->thresholds);
> + INIT_LIST_HEAD(&mem->memsw_thresholds);
> +
> + mem->below_threshold = mem_cgroup_threshold_alloc();
> + list_add(&mem->below_threshold->list, &mem->thresholds);
> + mem->below_threshold->threshold = 0ULL;
> +
> + mem->above_threshold = mem_cgroup_threshold_alloc();
> + list_add_tail(&mem->above_threshold->list, &mem->thresholds);
> + mem->above_threshold->threshold = RESOURCE_MAX;
> +
> + mem->memsw_below_threshold = mem_cgroup_threshold_alloc();
> + list_add(&mem->memsw_below_threshold->list, &mem->memsw_thresholds);
> + mem->memsw_below_threshold->threshold = 0ULL;
> +
> + mem->memsw_above_threshold = mem_cgroup_threshold_alloc();
> + list_add_tail(&mem->memsw_above_threshold->list, &mem->memsw_thresholds);
> + mem->memsw_above_threshold->threshold = RESOURCE_MAX;
> +
> + return 0;
> +}
> +
> +static void mem_cgroup_thresholds_free(struct mem_cgroup *mem)
> +{
> + /* Make sure that lists have only two elements */
> + BUG_ON((mem->below_threshold) &&
> + (mem->above_threshold) &&
> + (mem->below_threshold->list.next !=
> + &mem->above_threshold->list));
> + BUG_ON((mem->memsw_below_threshold) &&
> + (mem->memsw_above_threshold) &&
> + (mem->below_threshold->list.next !=
> + &mem->above_threshold->list));
> +
> + kfree(mem->below_threshold);
> + kfree(mem->above_threshold);
> + kfree(mem->memsw_below_threshold);
> + kfree(mem->memsw_above_threshold);
> +}
> +
> static int mem_cgroup_size(void)
> {
> int cpustat_size = nr_cpu_ids * sizeof(struct mem_cgroup_stat_cpu);
> @@ -3026,6 +3282,8 @@ static void __mem_cgroup_free(struct mem_cgroup *mem)
> {
> int node;
>
> + mem_cgroup_thresholds_free(mem);
> +
> mem_cgroup_remove_from_trees(mem);
> free_css_id(&mem_cgroup_subsys, &mem->css);
>
> @@ -3145,6 +3403,11 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
> mem->last_scanned_child = 0;
> spin_lock_init(&mem->reclaim_param_lock);
>
> + spin_lock_init(&mem->thresholds_lock);
> + error = mem_cgroup_thresholds_init(mem);
> + if (error)
> + goto free_out;
> +
> if (parent)
> mem->swappiness = get_swappiness(parent);
> atomic_set(&mem->refcnt, 1);
> --
> 1.6.5.3
>
>
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