From 26251eaf98e26dc2ce2dc26d63bc502700760704 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Thu, 1 Oct 2009 15:44:08 -0700 Subject: memcg: fix refcnt going negative __mem_cgroup_largest_soft_limit_node() returns a mem_cgroup_per_zone "mz" with incremnted mz->mem->css's refcnt. Then, the caller of this function has to call css_put(mz->mem->css). But, mz can be !NULL even if "not found" i.e. without css_get(). By this, css->refcnt will go down to minus. This may cause various things...one of results will be initite-loop in css_tryget() as this. INFO: RCU detected CPU 0 stall (t=10000 jiffies) sending NMI to all CPUs: NMI backtrace for cpu 0 CPU 0: <> [] trace_hardirqs_off+0xd/0x10 [] flat_send_IPI_mask+0x90/0xb0 [] flat_send_IPI_all+0x69/0x70 [] arch_trigger_all_cpu_backtrace+0x62/0xa0 [] __rcu_pending+0x7e/0x370 [] rcu_check_callbacks+0x47/0x130 [] update_process_times+0x46/0x70 [] tick_sched_timer+0x60/0x160 [] ? tick_sched_timer+0x0/0x160 [] __run_hrtimer+0xba/0x150 [] hrtimer_interrupt+0xd5/0x1b0 [] ? trace_hardirqs_off_thunk+0x3a/0x3c [] smp_apic_timer_interrupt+0x6d/0x9b [] apic_timer_interrupt+0x13/0x20 [] ? mem_cgroup_walk_tree+0x156/0x180 [] ? mem_cgroup_walk_tree+0x73/0x180 [] ? mem_cgroup_walk_tree+0x32/0x180 [] ? mem_cgroup_get_local_stat+0x0/0x110 [] ? mem_control_stat_show+0x14b/0x330 [] ? cgroup_seqfile_show+0x3d/0x60 Above shows CPU0 caught in css_tryget()'s inifinite loop because of bad refcnt. This is a fix to set mz=NULL at the top of retry path. Signed-off-by: KAMEZAWA Hiroyuki Acked-by: Paul Menage Cc: Li Zefan Cc: Balbir Singh Cc: Daisuke Nishimura Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e2b98a6875c0..21a30629ca80 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -447,9 +447,10 @@ static struct mem_cgroup_per_zone * __mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz) { struct rb_node *rightmost = NULL; - struct mem_cgroup_per_zone *mz = NULL; + struct mem_cgroup_per_zone *mz; retry: + mz = NULL; rightmost = rb_last(&mctz->rb_root); if (!rightmost) goto done; /* Nothing to reclaim from */ -- cgit v1.2.2 From 4e649152cbaa1aedd01821d200ab9d597fe469e4 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Thu, 1 Oct 2009 15:44:11 -0700 Subject: memcg: some modification to softlimit under hierarchical memory reclaim. This patch clean up/fixes for memcg's uncharge soft limit path. Problems: Now, res_counter_charge()/uncharge() handles softlimit information at charge/uncharge and softlimit-check is done when event counter per memcg goes over limit. Now, event counter per memcg is updated only when memory usage is over soft limit. Here, considering hierarchical memcg management, ancesotors should be taken care of. Now, ancerstors(hierarchy) are handled in charge() but not in uncharge(). This is not good. Prolems: 1. memcg's event counter incremented only when softlimit hits. That's bad. It makes event counter hard to be reused for other purpose. 2. At uncharge, only the lowest level rescounter is handled. This is bug. Because ancesotor's event counter is not incremented, children should take care of them. 3. res_counter_uncharge()'s 3rd argument is NULL in most case. ops under res_counter->lock should be small. No "if" sentense is better. Fixes: * Removed soft_limit_xx poitner and checks in charge and uncharge. Do-check-only-when-necessary scheme works enough well without them. * make event-counter of memcg incremented at every charge/uncharge. (per-cpu area will be accessed soon anyway) * All ancestors are checked at soft-limit-check. This is necessary because ancesotor's event counter may never be modified. Then, they should be checked at the same time. Reviewed-by: Daisuke Nishimura Signed-off-by: KAMEZAWA Hiroyuki Cc: Paul Menage Cc: Li Zefan Cc: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 113 +++++++++++++++++++++++++------------------------------- 1 file changed, 50 insertions(+), 63 deletions(-) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 21a30629ca80..1ae8c439584a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -352,16 +352,6 @@ __mem_cgroup_remove_exceeded(struct mem_cgroup *mem, mz->on_tree = false; } -static void -mem_cgroup_insert_exceeded(struct mem_cgroup *mem, - struct mem_cgroup_per_zone *mz, - struct mem_cgroup_tree_per_zone *mctz) -{ - spin_lock(&mctz->lock); - __mem_cgroup_insert_exceeded(mem, mz, mctz); - spin_unlock(&mctz->lock); -} - static void mem_cgroup_remove_exceeded(struct mem_cgroup *mem, struct mem_cgroup_per_zone *mz, @@ -392,34 +382,40 @@ static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem) static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page) { - unsigned long long prev_usage_in_excess, new_usage_in_excess; - bool updated_tree = false; + unsigned long long new_usage_in_excess; struct mem_cgroup_per_zone *mz; struct mem_cgroup_tree_per_zone *mctz; - - mz = mem_cgroup_zoneinfo(mem, page_to_nid(page), page_zonenum(page)); + int nid = page_to_nid(page); + int zid = page_zonenum(page); mctz = soft_limit_tree_from_page(page); /* - * We do updates in lazy mode, mem's are removed - * lazily from the per-zone, per-node rb tree + * Necessary to update all ancestors when hierarchy is used. + * because their event counter is not touched. */ - prev_usage_in_excess = mz->usage_in_excess; - - new_usage_in_excess = res_counter_soft_limit_excess(&mem->res); - if (prev_usage_in_excess) { - mem_cgroup_remove_exceeded(mem, mz, mctz); - updated_tree = true; - } - if (!new_usage_in_excess) - goto done; - mem_cgroup_insert_exceeded(mem, mz, mctz); - -done: - if (updated_tree) { - spin_lock(&mctz->lock); - mz->usage_in_excess = new_usage_in_excess; - spin_unlock(&mctz->lock); + for (; mem; mem = parent_mem_cgroup(mem)) { + mz = mem_cgroup_zoneinfo(mem, nid, zid); + new_usage_in_excess = + res_counter_soft_limit_excess(&mem->res); + /* + * We have to update the tree if mz is on RB-tree or + * mem is over its softlimit. + */ + if (new_usage_in_excess || mz->on_tree) { + spin_lock(&mctz->lock); + /* if on-tree, remove it */ + if (mz->on_tree) + __mem_cgroup_remove_exceeded(mem, mz, mctz); + /* + * if over soft limit, insert again. mz->usage_in_excess + * will be updated properly. + */ + if (new_usage_in_excess) + __mem_cgroup_insert_exceeded(mem, mz, mctz); + else + mz->usage_in_excess = 0; + spin_unlock(&mctz->lock); + } } } @@ -1271,9 +1267,9 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, gfp_t gfp_mask, struct mem_cgroup **memcg, bool oom, struct page *page) { - struct mem_cgroup *mem, *mem_over_limit, *mem_over_soft_limit; + struct mem_cgroup *mem, *mem_over_limit; int nr_retries = MEM_CGROUP_RECLAIM_RETRIES; - struct res_counter *fail_res, *soft_fail_res = NULL; + struct res_counter *fail_res; if (unlikely(test_thread_flag(TIF_MEMDIE))) { /* Don't account this! */ @@ -1305,17 +1301,16 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, if (mem_cgroup_is_root(mem)) goto done; - ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res, - &soft_fail_res); + ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res); if (likely(!ret)) { if (!do_swap_account) break; ret = res_counter_charge(&mem->memsw, PAGE_SIZE, - &fail_res, NULL); + &fail_res); if (likely(!ret)) break; /* mem+swap counter fails */ - res_counter_uncharge(&mem->res, PAGE_SIZE, NULL); + res_counter_uncharge(&mem->res, PAGE_SIZE); flags |= MEM_CGROUP_RECLAIM_NOSWAP; mem_over_limit = mem_cgroup_from_res_counter(fail_res, memsw); @@ -1354,16 +1349,11 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, } } /* - * Insert just the ancestor, we should trickle down to the correct - * cgroup for reclaim, since the other nodes will be below their - * soft limit + * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree. + * if they exceeds softlimit. */ - if (soft_fail_res) { - mem_over_soft_limit = - mem_cgroup_from_res_counter(soft_fail_res, res); - if (mem_cgroup_soft_limit_check(mem_over_soft_limit)) - mem_cgroup_update_tree(mem_over_soft_limit, page); - } + if (mem_cgroup_soft_limit_check(mem)) + mem_cgroup_update_tree(mem, page); done: return 0; nomem: @@ -1438,10 +1428,9 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem, if (unlikely(PageCgroupUsed(pc))) { unlock_page_cgroup(pc); if (!mem_cgroup_is_root(mem)) { - res_counter_uncharge(&mem->res, PAGE_SIZE, NULL); + res_counter_uncharge(&mem->res, PAGE_SIZE); if (do_swap_account) - res_counter_uncharge(&mem->memsw, PAGE_SIZE, - NULL); + res_counter_uncharge(&mem->memsw, PAGE_SIZE); } css_put(&mem->css); return; @@ -1520,7 +1509,7 @@ static int mem_cgroup_move_account(struct page_cgroup *pc, goto out; if (!mem_cgroup_is_root(from)) - res_counter_uncharge(&from->res, PAGE_SIZE, NULL); + res_counter_uncharge(&from->res, PAGE_SIZE); mem_cgroup_charge_statistics(from, pc, false); page = pc->page; @@ -1540,7 +1529,7 @@ static int mem_cgroup_move_account(struct page_cgroup *pc, } if (do_swap_account && !mem_cgroup_is_root(from)) - res_counter_uncharge(&from->memsw, PAGE_SIZE, NULL); + res_counter_uncharge(&from->memsw, PAGE_SIZE); css_put(&from->css); css_get(&to->css); @@ -1611,9 +1600,9 @@ uncharge: css_put(&parent->css); /* uncharge if move fails */ if (!mem_cgroup_is_root(parent)) { - res_counter_uncharge(&parent->res, PAGE_SIZE, NULL); + res_counter_uncharge(&parent->res, PAGE_SIZE); if (do_swap_account) - res_counter_uncharge(&parent->memsw, PAGE_SIZE, NULL); + res_counter_uncharge(&parent->memsw, PAGE_SIZE); } return ret; } @@ -1804,8 +1793,7 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr, * calling css_tryget */ if (!mem_cgroup_is_root(memcg)) - res_counter_uncharge(&memcg->memsw, PAGE_SIZE, - NULL); + res_counter_uncharge(&memcg->memsw, PAGE_SIZE); mem_cgroup_swap_statistics(memcg, false); mem_cgroup_put(memcg); } @@ -1832,9 +1820,9 @@ void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem) if (!mem) return; if (!mem_cgroup_is_root(mem)) { - res_counter_uncharge(&mem->res, PAGE_SIZE, NULL); + res_counter_uncharge(&mem->res, PAGE_SIZE); if (do_swap_account) - res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL); + res_counter_uncharge(&mem->memsw, PAGE_SIZE); } css_put(&mem->css); } @@ -1849,7 +1837,6 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) struct page_cgroup *pc; struct mem_cgroup *mem = NULL; struct mem_cgroup_per_zone *mz; - bool soft_limit_excess = false; if (mem_cgroup_disabled()) return NULL; @@ -1889,10 +1876,10 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) } if (!mem_cgroup_is_root(mem)) { - res_counter_uncharge(&mem->res, PAGE_SIZE, &soft_limit_excess); + res_counter_uncharge(&mem->res, PAGE_SIZE); if (do_swap_account && (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)) - res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL); + res_counter_uncharge(&mem->memsw, PAGE_SIZE); } if (ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) mem_cgroup_swap_statistics(mem, true); @@ -1909,7 +1896,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) mz = page_cgroup_zoneinfo(pc); unlock_page_cgroup(pc); - if (soft_limit_excess && mem_cgroup_soft_limit_check(mem)) + if (mem_cgroup_soft_limit_check(mem)) mem_cgroup_update_tree(mem, page); /* at swapout, this memcg will be accessed to record to swap */ if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT) @@ -1987,7 +1974,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent) * This memcg can be obsolete one. We avoid calling css_tryget */ if (!mem_cgroup_is_root(memcg)) - res_counter_uncharge(&memcg->memsw, PAGE_SIZE, NULL); + res_counter_uncharge(&memcg->memsw, PAGE_SIZE); mem_cgroup_swap_statistics(memcg, false); mem_cgroup_put(memcg); } -- cgit v1.2.2 From ef8745c1e7fc5413d760b3b958f3fd3a0beaad72 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Thu, 1 Oct 2009 15:44:12 -0700 Subject: memcg: reduce check for softlimit excess In charge/uncharge/reclaim path, usage_in_excess is calculated repeatedly and it takes res_counter's spin_lock every time. This patch removes unnecessary calls for res_count_soft_limit_excess. Reviewed-by: Daisuke Nishimura Signed-off-by: KAMEZAWA Hiroyuki Cc: Paul Menage Cc: Li Zefan Cc: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1ae8c439584a..f99f5991d6bb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -313,7 +313,8 @@ soft_limit_tree_from_page(struct page *page) static void __mem_cgroup_insert_exceeded(struct mem_cgroup *mem, struct mem_cgroup_per_zone *mz, - struct mem_cgroup_tree_per_zone *mctz) + struct mem_cgroup_tree_per_zone *mctz, + unsigned long long new_usage_in_excess) { struct rb_node **p = &mctz->rb_root.rb_node; struct rb_node *parent = NULL; @@ -322,7 +323,9 @@ __mem_cgroup_insert_exceeded(struct mem_cgroup *mem, if (mz->on_tree) return; - mz->usage_in_excess = res_counter_soft_limit_excess(&mem->res); + mz->usage_in_excess = new_usage_in_excess; + if (!mz->usage_in_excess) + return; while (*p) { parent = *p; mz_node = rb_entry(parent, struct mem_cgroup_per_zone, @@ -382,7 +385,7 @@ static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem) static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page) { - unsigned long long new_usage_in_excess; + unsigned long long excess; struct mem_cgroup_per_zone *mz; struct mem_cgroup_tree_per_zone *mctz; int nid = page_to_nid(page); @@ -395,25 +398,21 @@ static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page) */ for (; mem; mem = parent_mem_cgroup(mem)) { mz = mem_cgroup_zoneinfo(mem, nid, zid); - new_usage_in_excess = - res_counter_soft_limit_excess(&mem->res); + excess = res_counter_soft_limit_excess(&mem->res); /* * We have to update the tree if mz is on RB-tree or * mem is over its softlimit. */ - if (new_usage_in_excess || mz->on_tree) { + if (excess || mz->on_tree) { spin_lock(&mctz->lock); /* if on-tree, remove it */ if (mz->on_tree) __mem_cgroup_remove_exceeded(mem, mz, mctz); /* - * if over soft limit, insert again. mz->usage_in_excess - * will be updated properly. + * Insert again. mz->usage_in_excess will be updated. + * If excess is 0, no tree ops. */ - if (new_usage_in_excess) - __mem_cgroup_insert_exceeded(mem, mz, mctz); - else - mz->usage_in_excess = 0; + __mem_cgroup_insert_exceeded(mem, mz, mctz, excess); spin_unlock(&mctz->lock); } } @@ -2221,6 +2220,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order, unsigned long reclaimed; int loop = 0; struct mem_cgroup_tree_per_zone *mctz; + unsigned long long excess; if (order > 0) return 0; @@ -2272,9 +2272,8 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order, break; } while (1); } - mz->usage_in_excess = - res_counter_soft_limit_excess(&mz->mem->res); __mem_cgroup_remove_exceeded(mz->mem, mz, mctz); + excess = res_counter_soft_limit_excess(&mz->mem->res); /* * One school of thought says that we should not add * back the node to the tree if reclaim returns 0. @@ -2283,8 +2282,8 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order, * memory to reclaim from. Consider this as a longer * term TODO. */ - if (mz->usage_in_excess) - __mem_cgroup_insert_exceeded(mz->mem, mz, mctz); + /* If excess == 0, no tree ops */ + __mem_cgroup_insert_exceeded(mz->mem, mz, mctz, excess); spin_unlock(&mctz->lock); css_put(&mz->mem->css); loop++; -- cgit v1.2.2