Commit d13d1443 authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
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memcg: handle swap caches 



SwapCache support for memory resource controller (memcg)

Before mem+swap controller, memcg itself should handle SwapCache in proper
way.  This is cut-out from it.

In current memcg, SwapCache is just leaked and the user can create tons of
SwapCache.  This is a leak of account and should be handled.

SwapCache accounting is done as following.

  charge (anon)
	- charged when it's mapped.
	  (because of readahead, charge at add_to_swap_cache() is not sane)
  uncharge (anon)
	- uncharged when it's dropped from swapcache and fully unmapped.
	  means it's not uncharged at unmap.
	  Note: delete from swap cache at swap-in is done after rmap information
	        is established.
  charge (shmem)
	- charged at swap-in. this prevents charge at add_to_page_cache().

  uncharge (shmem)
	- uncharged when it's dropped from swapcache and not on shmem's
	  radix-tree.

  at migration, check against 'old page' is modified to handle shmem.

Comparing to the old version discussed (and caused troubles), we have
advantages of
  - PCG_USED bit.
  - simple migrating handling.

So, situation is much easier than several months ago, maybe.

[hugh@veritas.com: memcg: handle swap caches build fix]
Reviewed-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Tested-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c1e862c1

Documentation/controllers/memory.txt

+5 −0
Original line number Diff line number Diff line
@@ -137,6 +137,11 @@ behind this approach is that a cgroup that aggressively uses a shared 
page will eventually get charged for it (once it is uncharged from

the cgroup that brought it in -- this will happen on memory pressure).



Exception: When you do swapoff and make swapped-out pages of shmem(tmpfs) to

be backed into memory in force, charges for pages are accounted against the

caller of swapoff rather than the users of shmem.





2.4 Reclaim



Each cgroup maintains a per cgroup LRU that consists of an active

include/linux/swap.h

+22 −0
Original line number Diff line number Diff line
@@ -333,6 +333,22 @@ static inline void disable_swap_token(void) 
	put_swap_token(swap_token_mm);

}



#ifdef CONFIG_CGROUP_MEM_RES_CTLR

extern int mem_cgroup_cache_charge_swapin(struct page *page,

				struct mm_struct *mm, gfp_t mask, bool locked);

extern void mem_cgroup_uncharge_swapcache(struct page *page);

#else

static inline

int mem_cgroup_cache_charge_swapin(struct page *page,

				struct mm_struct *mm, gfp_t mask, bool locked)

{

	return 0;

}

static inline void mem_cgroup_uncharge_swapcache(struct page *page)

{

}

#endif



#else /* CONFIG_SWAP */



#define nr_swap_pages				0L
@@ -409,6 +425,12 @@ static inline swp_entry_t get_swap_page(void) 
#define has_swap_token(x) 0

#define disable_swap_token() do { } while(0)



static inline int mem_cgroup_cache_charge_swapin(struct page *page,

			struct mm_struct *mm, gfp_t mask, bool locked)

{

	return 0;

}



#endif /* CONFIG_SWAP */

#endif /* __KERNEL__*/

#endif /* _LINUX_SWAP_H */

mm/memcontrol.c

+61 −6
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/memcontrol.h>

#include <linux/cgroup.h>

#include <linux/mm.h>

#include <linux/pagemap.h>

#include <linux/smp.h>

#include <linux/page-flags.h>

#include <linux/backing-dev.h>
@@ -139,6 +140,7 @@ enum charge_type { 
	MEM_CGROUP_CHARGE_TYPE_MAPPED,

	MEM_CGROUP_CHARGE_TYPE_SHMEM,	/* used by page migration of shmem */

	MEM_CGROUP_CHARGE_TYPE_FORCE,	/* used by force_empty */

	MEM_CGROUP_CHARGE_TYPE_SWAPOUT,	/* for accounting swapcache */

	NR_CHARGE_TYPE,

};
@@ -780,6 +782,33 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm, 
				MEM_CGROUP_CHARGE_TYPE_SHMEM, NULL);

}



#ifdef CONFIG_SWAP

int mem_cgroup_cache_charge_swapin(struct page *page,

			struct mm_struct *mm, gfp_t mask, bool locked)

{

	int ret = 0;



	if (mem_cgroup_subsys.disabled)

		return 0;

	if (unlikely(!mm))

		mm = &init_mm;

	if (!locked)

		lock_page(page);

	/*

	 * If not locked, the page can be dropped from SwapCache until

	 * we reach here.

	 */

	if (PageSwapCache(page)) {

		ret = mem_cgroup_charge_common(page, mm, mask,

				MEM_CGROUP_CHARGE_TYPE_SHMEM, NULL);

	}

	if (!locked)

		unlock_page(page);



	return ret;

}

#endif



void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)

{

	struct page_cgroup *pc;
@@ -817,6 +846,9 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) 
	if (mem_cgroup_subsys.disabled)

		return;



	if (PageSwapCache(page))

		return;



	/*

	 * Check if our page_cgroup is valid

	 */
@@ -825,12 +857,26 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) 
		return;



	lock_page_cgroup(pc);

	if ((ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED && page_mapped(page))

	     || !PageCgroupUsed(pc)) {

		/* This happens at race in zap_pte_range() and do_swap_page()*/

		unlock_page_cgroup(pc);

		return;



	if (!PageCgroupUsed(pc))

		goto unlock_out;



	switch (ctype) {

	case MEM_CGROUP_CHARGE_TYPE_MAPPED:

		if (page_mapped(page))

			goto unlock_out;

		break;

	case MEM_CGROUP_CHARGE_TYPE_SWAPOUT:

		if (!PageAnon(page)) {	/* Shared memory */

			if (page->mapping && !page_is_file_cache(page))

				goto unlock_out;

		} else if (page_mapped(page)) /* Anon */

				goto unlock_out;

		break;

	default:

		break;

	}



	ClearPageCgroupUsed(pc);

	mem = pc->mem_cgroup;
@@ -844,6 +890,10 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) 
	css_put(&mem->css);



	return;



unlock_out:

	unlock_page_cgroup(pc);

	return;

}



void mem_cgroup_uncharge_page(struct page *page)
@@ -863,6 +913,11 @@ void mem_cgroup_uncharge_cache_page(struct page *page) 
	__mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE);

}



void mem_cgroup_uncharge_swapcache(struct page *page)

{

	__mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_SWAPOUT);

}



/*

 * Before starting migration, account PAGE_SIZE to mem_cgroup that the old

 * page belongs to.
@@ -920,7 +975,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem, 
		ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;



	/* unused page is not on radix-tree now. */

	if (unused && ctype != MEM_CGROUP_CHARGE_TYPE_MAPPED)

	if (unused)

		__mem_cgroup_uncharge_common(unused, ctype);



	pc = lookup_page_cgroup(target);

mm/shmem.c

+16 −2
Original line number Diff line number Diff line
@@ -928,8 +928,12 @@ found: 
	error = 1;

	if (!inode)

		goto out;

	/* Charge page using GFP_HIGHUSER_MOVABLE while we can wait */

	error = mem_cgroup_cache_charge(page, current->mm, GFP_HIGHUSER_MOVABLE);

	/*

	 * Charge page using GFP_HIGHUSER_MOVABLE while we can wait.

	 * charged back to the user(not to caller) when swap account is used.

	 */

	error = mem_cgroup_cache_charge_swapin(page,

			current->mm, GFP_HIGHUSER_MOVABLE, true);

	if (error)

		goto out;

	error = radix_tree_preload(GFP_KERNEL);
@@ -1266,6 +1270,16 @@ repeat: 
				goto repeat;

			}

			wait_on_page_locked(swappage);

			/*

			 * We want to avoid charge at add_to_page_cache().

			 * charge against this swap cache here.

			 */

			if (mem_cgroup_cache_charge_swapin(swappage,

						current->mm, gfp, false)) {

				page_cache_release(swappage);

				error = -ENOMEM;

				goto failed;

			}

			page_cache_release(swappage);

			goto repeat;

		}

mm/swap_state.c

+1 −0
Original line number Diff line number Diff line
@@ -118,6 +118,7 @@ void __delete_from_swap_cache(struct page *page) 
	total_swapcache_pages--;

	__dec_zone_page_state(page, NR_FILE_PAGES);

	INC_CACHE_INFO(del_total);

	mem_cgroup_uncharge_swapcache(page);

}



/**

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