The patch titled memcg: use CSS ID in swap_cgroup for saving memory has been added to the -mm tree. Its filename is use-css-id-in-swap_cgroup-for-saving-memory-v4.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: memcg: use CSS ID in swap_cgroup for saving memory From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Try to use CSS ID for records in swap_cgroup. By this, on 64bit machine, size of swap_cgroup goes down to 2 bytes from 8bytes. This means, when 2GB of swap is equipped, (assume the page size is 4096bytes) From size of swap_cgroup = 2G/4k * 8 = 4Mbytes. To size of swap_cgroup = 2G/4k * 2 = 1Mbytes. Reduction is large. Of course, there are trade-offs. This CSS ID will add overhead to swap-in/swap-out/swap-free. But in general, - swap is a resource which the user tend to avoid use. - If swap is never used, swap_cgroup area is not used. - Reading traditional manuals, size of swap should be proportional to size of memory. Memory size of machine is increasing now. I think reducing size of swap_cgroup makes sense. Note: - ID->CSS lookup routine has no locks, it's under RCU-Read-Side. - memcg can be obsolete at rmdir() but not freed while refcnt from swap_cgroup is available. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Cc: Li Zefan <lizf@xxxxxxxxxxxxxx> Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> Cc: Balbir Singh <balbir@xxxxxxxxxx> Cc: Paul Menage <menage@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/page_cgroup.h | 13 ++---- mm/memcontrol.c | 69 ++++++++++++++++++++++++++++------ mm/page_cgroup.c | 32 ++++++--------- 3 files changed, 78 insertions(+), 36 deletions(-) diff -puN include/linux/page_cgroup.h~use-css-id-in-swap_cgroup-for-saving-memory-v4 include/linux/page_cgroup.h --- a/include/linux/page_cgroup.h~use-css-id-in-swap_cgroup-for-saving-memory-v4 +++ a/include/linux/page_cgroup.h @@ -91,24 +91,23 @@ static inline void page_cgroup_init(void #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP #include <linux/swap.h> -extern struct mem_cgroup * -swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem); -extern struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent); +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); extern void swap_cgroup_swapoff(int type); #else #include <linux/swap.h> static inline -struct mem_cgroup *swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem) +unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id) { - return NULL; + return 0; } static inline -struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent) +unsigned short lookup_swap_cgroup(swp_entry_t ent) { - return NULL; + return 0; } static inline int diff -puN mm/memcontrol.c~use-css-id-in-swap_cgroup-for-saving-memory-v4 mm/memcontrol.c --- a/mm/memcontrol.c~use-css-id-in-swap_cgroup-for-saving-memory-v4 +++ a/mm/memcontrol.c @@ -991,20 +991,41 @@ nomem: return -ENOMEM; } +/* + * A helper function to get mem_cgroup from ID. must be called under + * rcu_read_lock(). The caller must check css_is_removed() or some if + * it's concern. (dropping refcnt from swap can be called against removed + * memcg.) + */ +static struct mem_cgroup *mem_cgroup_lookup(unsigned short id) +{ + struct cgroup_subsys_state *css; + + /* ID 0 is unused ID */ + if (!id) + return NULL; + css = css_lookup(&mem_cgroup_subsys, id); + if (!css) + return NULL; + return container_of(css, struct mem_cgroup, css); +} + static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page) { - struct mem_cgroup *mem; + unsigned short id; + struct mem_cgroup *mem = NULL; swp_entry_t ent; if (!PageSwapCache(page)) return NULL; ent.val = page_private(page); - mem = lookup_swap_cgroup(ent); - if (!mem) - return NULL; - if (!css_tryget(&mem->css)) - return NULL; + id = lookup_swap_cgroup(ent); + rcu_read_lock(); + mem = mem_cgroup_lookup(id); + if (mem && !css_tryget(&mem->css)) + mem = NULL; + rcu_read_unlock(); return mem; } @@ -1265,12 +1286,22 @@ int mem_cgroup_cache_charge(struct page if (do_swap_account && !ret && PageSwapCache(page)) { swp_entry_t ent = {.val = page_private(page)}; + unsigned short id; /* avoid double counting */ - mem = swap_cgroup_record(ent, NULL); + id = swap_cgroup_record(ent, 0); + rcu_read_lock(); + mem = mem_cgroup_lookup(id); if (mem) { + /* + * We did swap-in. Then, this entry is doubly counted + * both in mem and memsw. We uncharge it, here. + * Recorded ID can be obsolete. We avoid calling + * css_tryget() + */ res_counter_uncharge(&mem->memsw, PAGE_SIZE); mem_cgroup_put(mem); } + rcu_read_unlock(); } return ret; } @@ -1335,13 +1366,21 @@ void mem_cgroup_commit_charge_swapin(str */ if (do_swap_account && PageSwapCache(page)) { swp_entry_t ent = {.val = page_private(page)}; + unsigned short id; struct mem_cgroup *memcg; - memcg = swap_cgroup_record(ent, NULL); + + id = swap_cgroup_record(ent, 0); + rcu_read_lock(); + memcg = mem_cgroup_lookup(id); if (memcg) { + /* + * This recorded memcg can be obsolete one. So, avoid + * calling css_tryget + */ res_counter_uncharge(&memcg->memsw, PAGE_SIZE); mem_cgroup_put(memcg); } - + rcu_read_unlock(); } /* add this page(page_cgroup) to the LRU we want. */ @@ -1462,7 +1501,7 @@ void mem_cgroup_uncharge_swapcache(struc MEM_CGROUP_CHARGE_TYPE_SWAPOUT); /* record memcg information */ if (do_swap_account && memcg) { - swap_cgroup_record(ent, memcg); + swap_cgroup_record(ent, css_id(&memcg->css)); mem_cgroup_get(memcg); } if (memcg) @@ -1477,15 +1516,23 @@ void mem_cgroup_uncharge_swapcache(struc void mem_cgroup_uncharge_swap(swp_entry_t ent) { struct mem_cgroup *memcg; + unsigned short id; if (!do_swap_account) return; - memcg = swap_cgroup_record(ent, NULL); + id = swap_cgroup_record(ent, 0); + rcu_read_lock(); + memcg = mem_cgroup_lookup(id); if (memcg) { + /* + * We uncharge this because swap is freed. + * This memcg can be obsolete one. We avoid calling css_tryget + */ res_counter_uncharge(&memcg->memsw, PAGE_SIZE); mem_cgroup_put(memcg); } + rcu_read_unlock(); } #endif diff -puN mm/page_cgroup.c~use-css-id-in-swap_cgroup-for-saving-memory-v4 mm/page_cgroup.c --- a/mm/page_cgroup.c~use-css-id-in-swap_cgroup-for-saving-memory-v4 +++ a/mm/page_cgroup.c @@ -285,12 +285,8 @@ struct swap_cgroup_ctrl { struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES]; -/* - * This 8bytes seems big..maybe we can reduce this when we can use "id" for - * cgroup rather than pointer. - */ struct swap_cgroup { - struct mem_cgroup *val; + unsigned short id; }; #define SC_PER_PAGE (PAGE_SIZE/sizeof(struct swap_cgroup)) #define SC_POS_MASK (SC_PER_PAGE - 1) @@ -342,10 +338,10 @@ not_enough_page: * @ent: swap entry to be recorded into * @mem: mem_cgroup to be recorded * - * Returns old value at success, NULL at failure. - * (Of course, old value can be NULL.) + * Returns old value at success, 0 at failure. + * (Of course, old value can be 0.) */ -struct mem_cgroup *swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem) +unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id) { int type = swp_type(ent); unsigned long offset = swp_offset(ent); @@ -354,18 +350,18 @@ struct mem_cgroup *swap_cgroup_record(sw struct swap_cgroup_ctrl *ctrl; struct page *mappage; struct swap_cgroup *sc; - struct mem_cgroup *old; + unsigned short old; if (!do_swap_account) - return NULL; + return 0; ctrl = &swap_cgroup_ctrl[type]; mappage = ctrl->map[idx]; sc = page_address(mappage); sc += pos; - old = sc->val; - sc->val = mem; + old = sc->id; + sc->id = id; return old; } @@ -374,9 +370,9 @@ struct mem_cgroup *swap_cgroup_record(sw * lookup_swap_cgroup - lookup mem_cgroup tied to swap entry * @ent: swap entry to be looked up. * - * Returns pointer to mem_cgroup at success. NULL at failure. + * Returns CSS ID of mem_cgroup at success. 0 at failure. (0 is invalid ID) */ -struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent) +unsigned short lookup_swap_cgroup(swp_entry_t ent) { int type = swp_type(ent); unsigned long offset = swp_offset(ent); @@ -385,16 +381,16 @@ struct mem_cgroup *lookup_swap_cgroup(sw struct swap_cgroup_ctrl *ctrl; struct page *mappage; struct swap_cgroup *sc; - struct mem_cgroup *ret; + unsigned short ret; if (!do_swap_account) - return NULL; + return 0; ctrl = &swap_cgroup_ctrl[type]; mappage = ctrl->map[idx]; sc = page_address(mappage); sc += pos; - ret = sc->val; + ret = sc->id; return ret; } @@ -432,7 +428,7 @@ int swap_cgroup_swapon(int type, unsigne printk(KERN_INFO "swap_cgroup: uses %ld bytes of vmalloc for pointer array space" - " and %ld bytes to hold mem_cgroup pointers on swap\n", + " and %ld bytes to hold mem_cgroup information per swap ents\n", array_size, length * PAGE_SIZE); printk(KERN_INFO "swap_cgroup can be disabled by noswapaccount boot option.\n"); _ Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are linux-next.patch proc-pid-maps-dont-show-pgoff-of-pure-anon-vmas.patch proc-pid-maps-dont-show-pgoff-of-pure-anon-vmas-checkpatch-fixes.patch mm-introduce-for_each_populated_zone-macro.patch mm-introduce-for_each_populated_zone-macro-cleanup.patch vmscan-respect-higher-order-in-zone_reclaim.patch cgroup-css-id-support.patch cgroup-fix-frequent-ebusy-at-rmdir.patch cgroups-more-documentation-for-remount-and-release_agent.patch memcg-use-css-id.patch memcg-hierarchical-stat.patch memcg-fix-shrinking-memory-to-return-ebusy-by-fixing-retry-algorithm.patch memcg-fix-oom-killer-under-memcg.patch memcg-fix-oom-killer-under-memcg-fix2.patch memcg-fix-oom-killer-under-memcg-fix.patch memcg-show-memcg-information-during-oom.patch memcg-show-memcg-information-during-oom-fix2.patch memcg-show-memcg-information-during-oom-fix.patch memcg-show-memcg-information-during-oom-fix-fix.patch memcg-show-memcg-information-during-oom-fix-fix-checkpatch-fixes.patch memcg-remove-mem_cgroup_calc_mapped_ratio-take2.patch memcg-remove-mem_cgroup_reclaim_imbalance-remnants.patch use-css-id-in-swap_cgroup-for-saving-memory-v4.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html