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Subject[PATCH -mm][preview] memcg: a patch series for next [4/9]
Making freeing page_cgroup() at mem_cgroup_uncharge() to use lazy manner.

In mem_cgroup_uncharge_common(), we don't free page_cgroup
and just link it to per-cpu free queue.
And remove it later by checking threshold.

This patch is a base patch for freeing page_cgroup by RCU patch.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


---
mm/memcontrol.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 103 insertions(+), 17 deletions(-)

Index: linux-2.6.27-rc1-mm1/mm/memcontrol.c
===================================================================
--- linux-2.6.27-rc1-mm1.orig/mm/memcontrol.c
+++ linux-2.6.27-rc1-mm1/mm/memcontrol.c
@@ -167,6 +167,7 @@ struct page_cgroup {
struct page *page;
struct mem_cgroup *mem_cgroup;
unsigned long flags;
+ struct page_cgroup *next; /* used for Lazy LRU */
};

/* These 2 flags are unchanged during being used. */
@@ -174,6 +175,21 @@ struct page_cgroup {
#define PAGE_CG_FLAG_FILE (1) /* page is file system backed */
#define PAGE_CG_FLAG_ACTIVE (2) /* page is active in this cgroup */
#define PAGE_CG_FLAG_UNEVICTABLE (3) /* page is unevictableable */
+#define PAGE_CG_FLAG_OBSOLETE (4) /* page is unevictableable */
+
+#define MEMCG_LRU_THRESH (16)
+
+/*
+ * per-cpu slot for freeing page_cgroup in lazy way.
+ */
+
+struct mem_cgroup_lazy_lru {
+ int count;
+ struct page_cgroup *next;
+};
+
+DEFINE_PER_CPU(struct mem_cgroup_lazy_lru, memcg_lazy_lru);
+

static inline void page_cgroup_set_bit(struct page_cgroup *pc, int flag)
{
@@ -495,10 +511,12 @@ void mem_cgroup_move_lists(struct page *

pc = page_get_page_cgroup(page);
if (pc) {
- mz = page_cgroup_zoneinfo(pc);
- spin_lock_irqsave(&mz->lru_lock, flags);
- __mem_cgroup_move_lists(pc, lru);
- spin_unlock_irqrestore(&mz->lru_lock, flags);
+ if (!page_cgroup_test_bit(pc, PAGE_CG_FLAG_OBSOLETE)) {
+ mz = page_cgroup_zoneinfo(pc);
+ spin_lock_irqsave(&mz->lru_lock, flags);
+ __mem_cgroup_move_lists(pc, lru);
+ spin_unlock_irqrestore(&mz->lru_lock, flags);
+ }
}
unlock_page_cgroup(page);
}
@@ -592,6 +610,8 @@ unsigned long mem_cgroup_isolate_pages(u
if (unlikely(!PageLRU(page)))
continue;

+ if (page_cgroup_test_bit(pc, PAGE_CG_FLAG_OBSOLETE))
+ continue;
/*
* TODO: play better with lumpy reclaim, grabbing anything.
*/
@@ -618,6 +638,75 @@ unsigned long mem_cgroup_isolate_pages(u
return nr_taken;
}

+void __mem_cgroup_drop_lru(void)
+{
+ struct mem_cgroup *memcg;
+ struct page_cgroup *pc, *next;
+ struct mem_cgroup_per_zone *mz, *page_mz;
+ struct mem_cgroup_lazy_lru *mll;
+ unsigned long flags;
+
+ mll = &get_cpu_var(memcg_lazy_lru);
+ next = mll->next;
+ mll->next = NULL;
+ mll->count = 0;
+ put_cpu_var(memcg_lazy_lru);
+
+ mz = NULL;
+
+ local_irq_save(flags);
+ while (next) {
+ pc = next;
+ next = pc->next;
+ prefetch(next);
+ page_mz = page_cgroup_zoneinfo(pc);
+ memcg = pc->mem_cgroup;
+ if (page_mz != mz) {
+ if (mz)
+ spin_unlock(&mz->lru_lock);
+ mz = page_mz;
+ spin_lock(&mz->lru_lock);
+ }
+ __mem_cgroup_remove_list(mz, pc);
+ css_put(&memcg->css);
+ kmem_cache_free(page_cgroup_cache, pc);
+ }
+ if (mz)
+ spin_unlock(&mz->lru_lock);
+ local_irq_restore(flags);
+
+ return;
+}
+
+static void mem_cgroup_drop_lru(struct page_cgroup *pc)
+{
+ int count;
+ struct mem_cgroup_lazy_lru *mll;
+
+ mll = &get_cpu_var(memcg_lazy_lru);
+ pc->next = mll->next;
+ mll->next = pc;
+ count = ++mll->count;
+ put_cpu_var(memcg_lazy_lru);
+
+ if (count >= MEMCG_LRU_THRESH)
+ __mem_cgroup_drop_lru();
+}
+
+
+static DEFINE_MUTEX(memcg_force_drain_mutex);
+static void mem_cgroup_local_force_drain(struct work_struct *work)
+{
+ __mem_cgroup_drop_lru();
+}
+
+static void mem_cgroup_all_force_drain(struct mem_cgroup *memcg)
+{
+ mutex_lock(&memcg_force_drain_mutex);
+ schedule_on_each_cpu(mem_cgroup_local_force_drain);
+ mutex_unlock(&memcg_force_drain_mutex);
+}
+
/*
* Charge the memory controller for page usage.
* Return
@@ -629,10 +718,10 @@ static int mem_cgroup_charge_common(stru
struct mem_cgroup *memcg)
{
struct mem_cgroup *mem;
+ struct mem_cgroup_per_zone *mz;
struct page_cgroup *pc;
- unsigned long flags;
unsigned long nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
- struct mem_cgroup_per_zone *mz;
+ unsigned long flags;

pc = kmem_cache_alloc(page_cgroup_cache, gfp_mask);
if (unlikely(pc == NULL))
@@ -683,6 +772,7 @@ static int mem_cgroup_charge_common(stru
pc->mem_cgroup = mem;
pc->page = page;
pc->flags = 0;
+ pc->next = NULL;
/*
* If a page is accounted as a page cache, insert to inactive list.
* If anon, insert to active list.
@@ -712,6 +802,7 @@ static int mem_cgroup_charge_common(stru
spin_unlock_irqrestore(&mz->lru_lock, flags);

unlock_page_cgroup(page);
+
done:
return 0;
out:
@@ -785,8 +876,6 @@ __mem_cgroup_uncharge_common(struct page
{
struct page_cgroup *pc;
struct mem_cgroup *mem;
- struct mem_cgroup_per_zone *mz;
- unsigned long flags;

if (mem_cgroup_subsys.disabled)
return;
@@ -806,19 +895,14 @@ __mem_cgroup_uncharge_common(struct page
|| page_mapped(page)))
goto unlock;

- mz = page_cgroup_zoneinfo(pc);
- spin_lock_irqsave(&mz->lru_lock, flags);
- __mem_cgroup_remove_list(mz, pc);
- spin_unlock_irqrestore(&mz->lru_lock, flags);
-
+ mem = pc->mem_cgroup;
+ prefetch(mem);
+ page_cgroup_set_bit(pc, PAGE_CG_FLAG_OBSOLETE);
page_assign_page_cgroup(page, NULL);
unlock_page_cgroup(page);
-
- mem = pc->mem_cgroup;
mem_counter_uncharge(mem, 1);
- css_put(&mem->css);
+ mem_cgroup_drop_lru(pc);

- kmem_cache_free(page_cgroup_cache, pc);
return;
unlock:
unlock_page_cgroup(page);
@@ -1011,6 +1095,7 @@ static int mem_cgroup_force_empty(struct
}
}
ret = 0;
+ mem_cgroup_all_force_drain(mem);
out:
css_put(&mem->css);
return ret;
@@ -1212,6 +1297,7 @@ static int alloc_mem_cgroup_per_zone_inf
for_each_lru(l)
INIT_LIST_HEAD(&mz->lists[l]);
}
+
return 0;
}



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