Messages in this thread Patch in this message | | | Date | Fri, 14 Nov 2008 19:17:11 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [PATCH 4/9] memcg: handle swap caches |
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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.
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
--- Documentation/controllers/memory.txt | 5 ++ include/linux/swap.h | 16 ++++++++ mm/memcontrol.c | 67 +++++++++++++++++++++++++++++++---- mm/shmem.c | 18 ++++++++- mm/swap_state.c | 1 5 files changed, 99 insertions(+), 8 deletions(-)
Index: mmotm-2.6.28-Nov13/mm/memcontrol.c =================================================================== --- mmotm-2.6.28-Nov13.orig/mm/memcontrol.c +++ mmotm-2.6.28-Nov13/mm/memcontrol.c @@ -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 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 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 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 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(stru __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 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); Index: mmotm-2.6.28-Nov13/mm/swap_state.c =================================================================== --- mmotm-2.6.28-Nov13.orig/mm/swap_state.c +++ mmotm-2.6.28-Nov13/mm/swap_state.c @@ -119,6 +119,7 @@ void __delete_from_swap_cache(struct pag total_swapcache_pages--; __dec_zone_page_state(page, NR_FILE_PAGES); INC_CACHE_INFO(del_total); + mem_cgroup_uncharge_swapcache(page); } /** Index: mmotm-2.6.28-Nov13/include/linux/swap.h =================================================================== --- mmotm-2.6.28-Nov13.orig/include/linux/swap.h +++ mmotm-2.6.28-Nov13/include/linux/swap.h @@ -335,6 +335,22 @@ static inline void disable_swap_token(vo 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 total_swap_pages 0 Index: mmotm-2.6.28-Nov13/mm/shmem.c =================================================================== --- mmotm-2.6.28-Nov13.orig/mm/shmem.c +++ mmotm-2.6.28-Nov13/mm/shmem.c @@ -920,8 +920,12 @@ 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); @@ -1258,6 +1262,16 @@ 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; } Index: mmotm-2.6.28-Nov13/Documentation/controllers/memory.txt =================================================================== --- mmotm-2.6.28-Nov13.orig/Documentation/controllers/memory.txt +++ mmotm-2.6.28-Nov13/Documentation/controllers/memory.txt @@ -137,6 +137,11 @@ behind this approach is that a cgroup th 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
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