/* memcontrol.c - Memory Controller
*
* Copyright IBM Corporation, 2007
* Author Balbir Singh <balbir@linux.vnet.ibm.com>
*
* Copyright 2007 OpenVZ SWsoft Inc
* Author: Pavel Emelianov <xemul@openvz.org>
*
* 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
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/res_counter.h>
#include <linux/memcontrol.h>
#include <linux/cgroup.h>
#include <linux/mm.h>
#include <linux/page-flags.h>
#include <linux/bit_spinlock.h>
#include <linux/rcupdate.h>
struct cgroup_subsys mem_cgroup_subsys;
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
* statistics based on the statistics developed by Rik Van Riel for clock-pro,
* to help the administrator determine what knobs to tune.
*
* TODO: Add a water mark for the memory controller. Reclaim will begin when
* we hit the water mark. May be even add a low water mark, such that
* no reclaim occurs from a cgroup at it's low water mark, this is
* a feature that will be implemented much later in the future.
*/
struct mem_cgroup {
struct cgroup_subsys_state css;
/*
* the counter to account for memory usage
*/
struct res_counter res;
/*
* Per cgroup active and inactive list, similar to the
* per zone LRU lists.
* TODO: Consider making these lists per zone
*/
struct list_head active_list;
struct list_head inactive_list;
};
/*
* We use the lower bit of the page->page_cgroup pointer as a bit spin
* lock. We need to ensure that page->page_cgroup is atleast two
* byte aligned (based on comments from Nick Piggin)
*/
#define PAGE_CGROUP_LOCK_BIT 0x0
#define PAGE_CGROUP_LOCK (1 << PAGE_CGROUP_LOCK_BIT)
/*
* A page_cgroup page is associated with every page descriptor. The
* page_cgroup helps us identify information about the cgroup
*/
struct page_cgroup {
struct list_head lru; /* per cgroup LRU list */
struct page *page;
struct mem_cgroup *mem_cgroup;
atomic_t ref_cnt; /* Helpful when pages move b/w */
/* mapped and cached states */
};
static inline
struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
{
return container_of(cgroup_subsys_state(cont,
mem_cgroup_subsys_id), struct mem_cgroup,
css);
}
static inline
struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
{
return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
struct mem_cgroup, css);
}
void mm_init_cgroup(struct mm_struct *mm, struct task_struct *p)
{
struct mem_cgroup *mem;
mem = mem_cgroup_from_task(p);
css_get(&mem->css);
mm->mem_cgroup = mem;
}
void mm_free_cgroup(struct mm_struct *mm)
{
css_put(&mm->mem_cgroup->css);
}
static inline int page_cgroup_locked(struct page *page)
{
return bit_spin_is_locked(PAGE_CGROUP_LOCK_BIT,
&page->page_cgroup);
}
void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
{
int locked;
/*
* While resetting the page_cgroup we might not hold the
* page_cgroup lock. free_hot_cold_page() is an example
* of such a scenario
*/
if (pc)
VM_BUG_ON(!page_cgroup_locked(page));
locked = (page->page_cgroup & PAGE_CGROUP_LOCK);
page->page_cgroup = ((unsigned long)pc | locked);
}
struct page_cgroup *page_get_page_cgroup(struct page *page)
{
return (struct page_cgroup *)
(page->page_cgroup & ~PAGE_CGROUP_LOCK);
}
void __always_inline lock_page_cgroup(struct page *page)
{
bit_spin_lock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
VM_BUG_ON(!page_cgroup_locked(page));
}
void __always_inline unlock_page_cgroup(struct page *page)
{
bit_spin_unlock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
}
/*
* Charge the memory controller for page usage.
* Return
* 0 if the charge was successful
* < 0 if the cgroup is over its limit
*/
int mem_cgroup_charge(struct page *page, struct mm_struct *mm)
{
struct mem_cgroup *mem;
struct page_cgroup *pc, *race_pc;
/*
* Should page_cgroup's go to their own slab?
* One could optimize the performance of the charging routine
* by saving a bit in the page_flags and using it as a lock
* to see if the cgroup page already has a page_cgroup associated
* with it
*/
lock_page_cgroup(page);
pc = page_get_page_cgroup(page);
/*
* The page_cgroup exists and the page has already been accounted
*/
if (pc) {
atomic_inc(&pc->ref_cnt);
goto done;
}
unlock_page_cgroup(page);
pc = kzalloc(sizeof(struct page_cgroup), GFP_KERNEL);
if (pc == NULL)
goto err;
rcu_read_lock();
/*
* We always charge the cgroup the mm_struct belongs to
* the mm_struct's mem_cgroup changes on task migration if the
* thread group leader migrates. It's possible that mm is not
* set, if so charge the init_mm (happens for pagecache usage).
*/
if (!mm)
mm = &init_mm;
mem = rcu_dereference(mm->mem_cgroup);
/*
* For every charge from the cgroup, increment reference
* count
*/
css_get(&mem->css);
rcu_read_unlock();
/*
* If we created the page_cgroup, we should free it on exceeding
* the cgroup limit.
*/
if (res_counter_charge(&mem->res, 1)) {
css_put(&mem->css);
goto free_pc;
}
lock_page_cgroup(page);
/*
* Check if somebody else beat us to allocating the page_cgroup
*/
race_pc = page_get_page_cgroup(page);
if (race_pc) {
kfree(pc);
pc = race_pc;
atomic_inc(&pc->ref_cnt);
res_counter_uncharge(&mem->res, 1);
css_put(&mem->css);
goto done;
}
atomic_set(&pc->ref_cnt, 1);
pc->mem_cgroup = mem;
pc->page = page;
page_assign_page_cgroup(page, pc);
done:
unlock_page_cgroup(page);
return 0;
free_pc:
kfree(pc);
return -ENOMEM;
err:
unlock_page_cgroup(page);
return -ENOMEM;
}
/*
* Uncharging is always a welcome operation, we never complain, simply
* uncharge.
*/
void mem_cgroup_uncharge(struct page_cgroup *pc)
{
struct mem_cgroup *mem;
struct page *page;
if (!pc)
return;
if (atomic_dec_and_test(&pc->ref_cnt)) {
page = pc->page;
lock_page_cgroup(page);
mem = pc->mem_cgroup;
css_put(&mem->css);
page_assign_page_cgroup(page, NULL);
unlock_page_cgroup(page);
res_counter_uncharge(&mem->res, 1);
kfree(pc);
}
}
static ssize_t mem_cgroup_read(struct cgroup *cont, struct cftype *cft,
struct file *file, char __user *userbuf, size_t nbytes,
loff_t *ppos)
{
return res_counter_read(&mem_cgroup_from_cont(cont)->res,
cft->private, userbuf, nbytes, ppos);
}
static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
struct file *file, const char __user *userbuf,
size_t nbytes, loff_t *ppos)
{
return res_counter_write(&mem_cgroup_from_cont(cont)->res,
cft->private, userbuf, nbytes, ppos);
}
static struct cftype mem_cgroup_files[] = {
{
.name = "usage",
.private = RES_USAGE,
.read = mem_cgroup_read,
},
{
.name = "limit",
.private = RES_LIMIT,
.write = mem_cgroup_write,
.read = mem_cgroup_read,
},
{
.name = "failcnt",
.private = RES_FAILCNT,
.read = mem_cgroup_read,
},
};
static struct mem_cgroup init_mem_cgroup;
static struct cgroup_subsys_state *
mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
{
struct mem_cgroup *mem;
if (unlikely((cont->parent) == NULL)) {
mem = &init_mem_cgroup;
init_mm.mem_cgroup = mem;
} else
mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);
if (mem == NULL)
return NULL;
res_counter_init(&mem->res);
INIT_LIST_HEAD(&mem->active_list);
INIT_LIST_HEAD(&mem->inactive_list);
return &mem->css;
}
static void mem_cgroup_destroy(struct cgroup_subsys *ss,
struct cgroup *cont)
{
kfree(mem_cgroup_from_cont(cont));
}
static int mem_cgroup_populate(struct cgroup_subsys *ss,
struct cgroup *cont)
{
return cgroup_add_files(cont, ss, mem_cgroup_files,
ARRAY_SIZE(mem_cgroup_files));
}
struct cgroup_subsys mem_cgroup_subsys = {
.name = "memory",
.subsys_id = mem_cgroup_subsys_id,
.create = mem_cgroup_create,
.destroy = mem_cgroup_destroy,
.populate = mem_cgroup_populate,
.early_init = 1,
};
