From 483c30b514bd3037fa3f19fa42327c94c10f51c8 Mon Sep 17 00:00:00 2001 From: Daisuke Nishimura Date: Wed, 10 Mar 2010 15:22:18 -0800 Subject: [PATCH] memcg: improve performance in moving swap charge Try to reduce overheads in moving swap charge by: - Adds a new function(__mem_cgroup_put), which takes "count" as a arg and decrement mem->refcnt by "count". - Removed res_counter_uncharge, css_put, and mem_cgroup_put from the path of moving swap account, and consolidate all of them into mem_cgroup_clear_mc. We cannot do that about mc.to->refcnt. These changes reduces the overhead from 1.35sec to 0.9sec to move charges of 1G anonymous memory(including 500MB swap) in my test environment. Signed-off-by: Daisuke Nishimura Cc: Balbir Singh Acked-by: KAMEZAWA Hiroyuki Cc: Li Zefan Cc: Paul Menage Cc: Daisuke Nishimura Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 77 +++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 61 insertions(+), 16 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e883198baf81..b00ec74a4c18 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -255,6 +255,7 @@ static struct move_charge_struct { struct mem_cgroup *to; unsigned long precharge; unsigned long moved_charge; + unsigned long moved_swap; struct task_struct *moving_task; /* a task moving charges */ wait_queue_head_t waitq; /* a waitq for other context */ } mc = { @@ -2277,6 +2278,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent) * @entry: swap entry to be moved * @from: mem_cgroup which the entry is moved from * @to: mem_cgroup which the entry is moved to + * @need_fixup: whether we should fixup res_counters and refcounts. * * It succeeds only when the swap_cgroup's record for this entry is the same * as the mem_cgroup's id of @from. @@ -2287,7 +2289,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent) * 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) + struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup) { unsigned short old_id, new_id; @@ -2295,27 +2297,36 @@ static int mem_cgroup_move_swap_account(swp_entry_t entry, 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); + /* + * This function is only called from task migration context now. + * It postpones res_counter and refcount handling till the end + * of task migration(mem_cgroup_clear_mc()) for performance + * improvement. But we cannot postpone mem_cgroup_get(to) + * because if the process that has been moved to @to does + * swap-in, the refcount of @to might be decreased to 0. + */ mem_cgroup_get(to); - css_put(&to->css); - + if (need_fixup) { + if (!mem_cgroup_is_root(from)) + res_counter_uncharge(&from->memsw, PAGE_SIZE); + 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); + 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) + struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup) { return -EINVAL; } @@ -3398,9 +3409,9 @@ static void mem_cgroup_get(struct mem_cgroup *mem) atomic_inc(&mem->refcnt); } -static void mem_cgroup_put(struct mem_cgroup *mem) +static void __mem_cgroup_put(struct mem_cgroup *mem, int count) { - if (atomic_dec_and_test(&mem->refcnt)) { + if (atomic_sub_and_test(count, &mem->refcnt)) { struct mem_cgroup *parent = parent_mem_cgroup(mem); __mem_cgroup_free(mem); if (parent) @@ -3408,6 +3419,11 @@ static void mem_cgroup_put(struct mem_cgroup *mem) } } +static void mem_cgroup_put(struct mem_cgroup *mem) +{ + __mem_cgroup_put(mem, 1); +} + /* * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled. */ @@ -3789,6 +3805,29 @@ static void mem_cgroup_clear_mc(void) __mem_cgroup_cancel_charge(mc.from, mc.moved_charge); mc.moved_charge = 0; } + /* we must fixup refcnts and charges */ + if (mc.moved_swap) { + WARN_ON_ONCE(mc.moved_swap > INT_MAX); + /* uncharge swap account from the old cgroup */ + if (!mem_cgroup_is_root(mc.from)) + res_counter_uncharge(&mc.from->memsw, + PAGE_SIZE * mc.moved_swap); + __mem_cgroup_put(mc.from, mc.moved_swap); + + if (!mem_cgroup_is_root(mc.to)) { + /* + * we charged both to->res and to->memsw, so we should + * uncharge to->res. + */ + res_counter_uncharge(&mc.to->res, + PAGE_SIZE * mc.moved_swap); + VM_BUG_ON(test_bit(CSS_ROOT, &mc.to->css.flags)); + __css_put(&mc.to->css, mc.moved_swap); + } + /* we've already done mem_cgroup_get(mc.to) */ + + mc.moved_swap = 0; + } mc.from = NULL; mc.to = NULL; mc.moving_task = NULL; @@ -3818,11 +3857,13 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss, VM_BUG_ON(mc.to); VM_BUG_ON(mc.precharge); VM_BUG_ON(mc.moved_charge); + VM_BUG_ON(mc.moved_swap); VM_BUG_ON(mc.moving_task); mc.from = from; mc.to = mem; mc.precharge = 0; mc.moved_charge = 0; + mc.moved_swap = 0; mc.moving_task = current; ret = mem_cgroup_precharge_mc(mm); @@ -3883,8 +3924,12 @@ put: /* is_target_pte_for_mc() gets the page */ break; case MC_TARGET_SWAP: ent = target.ent; - if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to)) + if (!mem_cgroup_move_swap_account(ent, + mc.from, mc.to, false)) { mc.precharge--; + /* we fixup refcnts and charges later. */ + mc.moved_swap++; + } break; default: break;