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memcg: move charges of anonymous swap

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This patch is another core part of this move-charge-at-task-migration
feature.  It enables moving charges of anonymous swaps.

To move the charge of swap, we need to exchange swap_cgroup's record.

In current implementation, swap_cgroup's record is protected by:

  - page lock: if the entry is on swap cache.
  - swap_lock: if the entry is not on swap cache.

This works well in usual swap-in/out activity.

But this behavior make the feature of moving swap charge check many
conditions to exchange swap_cgroup's record safely.

So I changed modification of swap_cgroup's recored(swap_cgroup_record())
to use xchg, and define a new function to cmpxchg swap_cgroup's record.

This patch also enables moving charge of non pte_present but not uncharged
swap caches, which can be exist on swap-out path, by getting the target
pages via find_get_page() as do_mincore() does.

[kosaki.motohiro@jp.fujitsu.com: fix ia64 build]
[akpm@linux-foundation.org: fix typos]
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Daisuke Nishimura 2010-03-10 15:22:17 -08:00 committed by Linus Torvalds
parent 8033b97c9b
commit 024914477e
6 changed files with 225 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/cgroups/memory.txt
View File

@ -420,6 +420,8 @@ NOTE2: It is recommended to set the soft limit always below the hard limit,
Users can move charges associated with a task along with task migration, that
is, uncharge task's pages from the old cgroup and charge them to the new cgroup.
This feature is not supported in !CONFIG_MMU environments because of lack of
page tables.
8.1 Interface

2
include/linux/page_cgroup.h
View File

@ -118,6 +118,8 @@ static inline void __init page_cgroup_init_flatmem(void)
#include <linux/swap.h>
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
extern unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
unsigned short old, unsigned short new);
extern unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id);
extern unsigned short lookup_swap_cgroup(swp_entry_t ent);
extern int swap_cgroup_swapon(int type, unsigned long max_pages);

9
include/linux/swap.h
View File

@ -355,6 +355,7 @@ static inline void disable_swap_token(void)
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
extern void
mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout);
extern int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep);
#else
static inline void
mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
@ -485,6 +486,14 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
{
}
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
static inline int
mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
{
return 0;
}
#endif
#endif /* CONFIG_SWAP */
#endif /* __KERNEL__*/
#endif /* _LINUX_SWAP_H */

187
mm/memcontrol.c
View File

@ -33,6 +33,7 @@
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/spinlock.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
@ -2270,6 +2271,54 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)
}
rcu_read_unlock();
}
/**
* mem_cgroup_move_swap_account - move swap charge and swap_cgroup's record.
* @entry: swap entry to be moved
* @from: mem_cgroup which the entry is moved from
* @to: mem_cgroup which the entry is moved to
*
* It succeeds only when the swap_cgroup's record for this entry is the same
* as the mem_cgroup's id of @from.
*
* Returns 0 on success, -EINVAL on failure.
*
* The caller must have charged to @to, IOW, called res_counter_charge() about
* both res and memsw, and called css_get().
*/
static int mem_cgroup_move_swap_account(swp_entry_t entry,
struct mem_cgroup *from, struct mem_cgroup *to)
{
unsigned short old_id, new_id;
old_id = css_id(&from->css);
new_id = css_id(&to->css);
if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
if (!mem_cgroup_is_root(from))
res_counter_uncharge(&from->memsw, PAGE_SIZE);
mem_cgroup_swap_statistics(from, false);
mem_cgroup_put(from);
/*
* we charged both to->res and to->memsw, so we should uncharge
* to->res.
*/
if (!mem_cgroup_is_root(to))
res_counter_uncharge(&to->res, PAGE_SIZE);
mem_cgroup_swap_statistics(to, true);
mem_cgroup_get(to);
css_put(&to->css);
return 0;
}
return -EINVAL;
}
#else
static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
struct mem_cgroup *from, struct mem_cgroup *to)
{
return -EINVAL;
}
#endif
/*
@ -2949,6 +2998,7 @@ static u64 mem_cgroup_move_charge_read(struct cgroup *cgrp,
return mem_cgroup_from_cont(cgrp)->move_charge_at_immigrate;
}
#ifdef CONFIG_MMU
static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
struct cftype *cft, u64 val)
{
@ -2967,6 +3017,13 @@ static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
return 0;
}
#else
static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
struct cftype *cft, u64 val)
{
return -ENOSYS;
}
#endif
/* For read statistics */
@ -3489,6 +3546,7 @@ static int mem_cgroup_populate(struct cgroup_subsys *ss,
return ret;
}
#ifdef CONFIG_MMU
/* Handlers for move charge at task migration. */
#define PRECHARGE_COUNT_AT_ONCE 256
static int mem_cgroup_do_precharge(unsigned long count)
@ -3544,77 +3602,124 @@ one_by_one:
}
return ret;
}
#else /* !CONFIG_MMU */
static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
struct task_struct *p,
bool threadgroup)
{
return 0;
}
static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
struct task_struct *p,
bool threadgroup)
{
}
static void mem_cgroup_move_task(struct cgroup_subsys *ss,
struct cgroup *cont,
struct cgroup *old_cont,
struct task_struct *p,
bool threadgroup)
{
}
#endif
/**
* is_target_pte_for_mc - check a pte whether it is valid for move charge
* @vma: the vma the pte to be checked belongs
* @addr: the address corresponding to the pte to be checked
* @ptent: the pte to be checked
* @target: the pointer the target page will be stored(can be NULL)
* @target: the pointer the target page or swap ent will be stored(can be NULL)
*
* Returns
* 0(MC_TARGET_NONE): if the pte is not a target for move charge.
* 1(MC_TARGET_PAGE): if the page corresponding to this pte is a target for
* move charge. if @target is not NULL, the page is stored in target->page
* with extra refcnt got(Callers should handle it).
* 2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
* target for charge migration. if @target is not NULL, the entry is stored
* in target->ent.
*
* Called with pte lock held.
*/
/* We add a new member later. */
union mc_target {
struct page *page;
swp_entry_t ent;
};
/* We add a new type later. */
enum mc_target_type {
MC_TARGET_NONE, /* not used */
MC_TARGET_PAGE,
MC_TARGET_SWAP,
};
static int is_target_pte_for_mc(struct vm_area_struct *vma,
unsigned long addr, pte_t ptent, union mc_target *target)
{
struct page *page;
struct page *page = NULL;
struct page_cgroup *pc;
int ret = 0;
swp_entry_t ent = { .val = 0 };
int usage_count = 0;
bool move_anon = test_bit(MOVE_CHARGE_TYPE_ANON,
&mc.to->move_charge_at_immigrate);
if (!pte_present(ptent))
return 0;
page = vm_normal_page(vma, addr, ptent);
if (!page || !page_mapped(page))
return 0;
/*
* TODO: We don't move charges of file(including shmem/tmpfs) pages for
* now.
*/
if (!move_anon || !PageAnon(page))
return 0;
/*
* TODO: We don't move charges of shared(used by multiple processes)
* pages for now.
*/
if (page_mapcount(page) > 1)
return 0;
if (!get_page_unless_zero(page))
return 0;
pc = lookup_page_cgroup(page);
/*
* Do only loose check w/o page_cgroup lock. mem_cgroup_move_account()
* checks the pc is valid or not under the lock.
*/
if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
if (target)
target->page = page;
if (!pte_present(ptent)) {
/* TODO: handle swap of shmes/tmpfs */
if (pte_none(ptent) || pte_file(ptent))
return 0;
else if (is_swap_pte(ptent)) {
ent = pte_to_swp_entry(ptent);
if (!move_anon || non_swap_entry(ent))
return 0;
usage_count = mem_cgroup_count_swap_user(ent, &page);
}
} else {
page = vm_normal_page(vma, addr, ptent);
if (!page || !page_mapped(page))
return 0;
/*
* TODO: We don't move charges of file(including shmem/tmpfs)
* pages for now.
*/
if (!move_anon || !PageAnon(page))
return 0;
if (!get_page_unless_zero(page))
return 0;
usage_count = page_mapcount(page);
}
if (usage_count > 1) {
/*
* TODO: We don't move charges of shared(used by multiple
* processes) pages for now.
*/
if (page)
put_page(page);
return 0;
}
if (page) {
pc = lookup_page_cgroup(page);
/*
* Do only loose check w/o page_cgroup lock.
* mem_cgroup_move_account() checks the pc is valid or not under
* the lock.
*/
if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
if (target)
target->page = page;
}
if (!ret || !target)
put_page(page);
}
/* throught */
if (ent.val && do_swap_account && !ret &&
css_id(&mc.from->css) == lookup_swap_cgroup(ent)) {
ret = MC_TARGET_SWAP;
if (target)
target->ent = ent;
}
if (!ret || !target)
put_page(page);
return ret;
}
@ -3754,6 +3859,7 @@ retry:
int type;
struct page *page;
struct page_cgroup *pc;
swp_entry_t ent;
if (!mc.precharge)
break;
@ -3775,6 +3881,11 @@ retry:
put: /* is_target_pte_for_mc() gets the page */
put_page(page);
break;
case MC_TARGET_SWAP:
ent = target.ent;
if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to))
mc.precharge--;
break;
default:
break;
}

34
mm/page_cgroup.c
View File

@ -334,6 +334,37 @@ not_enough_page:
return -ENOMEM;
}
/**
* swap_cgroup_cmpxchg - cmpxchg mem_cgroup's id for this swp_entry.
* @end: swap entry to be cmpxchged
* @old: old id
* @new: new id
*
* Returns old id at success, 0 at failure.
* (There is no mem_cgroup useing 0 as its id)
*/
unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
unsigned short old, unsigned short new)
{
int type = swp_type(ent);
unsigned long offset = swp_offset(ent);
unsigned long idx = offset / SC_PER_PAGE;
unsigned long pos = offset & SC_POS_MASK;
struct swap_cgroup_ctrl *ctrl;
struct page *mappage;
struct swap_cgroup *sc;
ctrl = &swap_cgroup_ctrl[type];
mappage = ctrl->map[idx];
sc = page_address(mappage);
sc += pos;
if (cmpxchg(&sc->id, old, new) == old)
return old;
else
return 0;
}
/**
* swap_cgroup_record - record mem_cgroup for this swp_entry.
* @ent: swap entry to be recorded into
@ -358,8 +389,7 @@ unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
mappage = ctrl->map[idx];
sc = page_address(mappage);
sc += pos;
old = sc->id;
sc->id = id;
old = xchg(&sc->id, id);
return old;
}

31
mm/swapfile.c
View File

@ -723,6 +723,37 @@ int free_swap_and_cache(swp_entry_t entry)
return p != NULL;
}
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
/**
* mem_cgroup_count_swap_user - count the user of a swap entry
* @ent: the swap entry to be checked
* @pagep: the pointer for the swap cache page of the entry to be stored
*
* Returns the number of the user of the swap entry. The number is valid only
* for swaps of anonymous pages.
* If the entry is found on swap cache, the page is stored to pagep with
* refcount of it being incremented.
*/
int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
{
struct page *page;
struct swap_info_struct *p;
int count = 0;
page = find_get_page(&swapper_space, ent.val);
if (page)
count += page_mapcount(page);
p = swap_info_get(ent);
if (p) {
count += swap_count(p->swap_map[swp_offset(ent)]);
spin_unlock(&swap_lock);
}
*pagep = page;
return count;
}
#endif
#ifdef CONFIG_HIBERNATION
/*
* Find the swap type that corresponds to given device (if any).