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Date: Mon, 20 Oct 2014 11:22:12 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Hugh Dickins <hughd@...gle.com>, Michal Hocko <mhocko@...e.cz>,
Vladimir Davydov <vdavydov@...allels.com>, linux-mm@...ck.org,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [patch 4/4] mm: memcontrol: remove unnecessary PCG_USED pc->mem_cgroup valid flag
pc->mem_cgroup had to be left intact after uncharge for the final LRU
removal, and !PCG_USED indicated whether the page was uncharged. But
since 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API") pages are
uncharged after the final LRU removal. Uncharge can simply clear the
pointer and the PCG_USED/PageCgroupUsed sites can test that instead.
Because this is the last page_cgroup flag, this patch reduces the
memcg per-page overhead to a single pointer.
Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
include/linux/page_cgroup.h | 10 -----
mm/memcontrol.c | 107 +++++++++++++++++---------------------------
2 files changed, 42 insertions(+), 75 deletions(-)
diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index 97536e685843..1289be6b436c 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -1,11 +1,6 @@
#ifndef __LINUX_PAGE_CGROUP_H
#define __LINUX_PAGE_CGROUP_H
-enum {
- /* flags for mem_cgroup */
- PCG_USED = 0x01, /* This page is charged to a memcg */
-};
-
struct pglist_data;
#ifdef CONFIG_MEMCG
@@ -19,7 +14,6 @@ struct mem_cgroup;
* then the page cgroup for pfn always exists.
*/
struct page_cgroup {
- unsigned long flags;
struct mem_cgroup *mem_cgroup;
};
@@ -39,10 +33,6 @@ static inline void page_cgroup_init(void)
struct page_cgroup *lookup_page_cgroup(struct page *page);
-static inline int PageCgroupUsed(struct page_cgroup *pc)
-{
- return !!(pc->flags & PCG_USED);
-}
#else /* !CONFIG_MEMCG */
struct page_cgroup;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1d66ac49e702..48d49c6b08d1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1284,14 +1284,12 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct zone *zone)
pc = lookup_page_cgroup(page);
memcg = pc->mem_cgroup;
-
/*
* Swapcache readahead pages are added to the LRU - and
- * possibly migrated - before they are charged. Ensure
- * pc->mem_cgroup is sane.
+ * possibly migrated - before they are charged.
*/
- if (!PageLRU(page) && !PageCgroupUsed(pc) && memcg != root_mem_cgroup)
- pc->mem_cgroup = memcg = root_mem_cgroup;
+ if (!memcg)
+ memcg = root_mem_cgroup;
mz = mem_cgroup_page_zoneinfo(memcg, page);
lruvec = &mz->lruvec;
@@ -2141,7 +2139,7 @@ void __mem_cgroup_begin_update_page_stat(struct page *page,
pc = lookup_page_cgroup(page);
again:
memcg = pc->mem_cgroup;
- if (unlikely(!memcg || !PageCgroupUsed(pc)))
+ if (unlikely(!memcg))
return;
/*
* If this memory cgroup is not under account moving, we don't
@@ -2154,7 +2152,7 @@ again:
return;
move_lock_mem_cgroup(memcg, flags);
- if (memcg != pc->mem_cgroup || !PageCgroupUsed(pc)) {
+ if (memcg != pc->mem_cgroup) {
move_unlock_mem_cgroup(memcg, flags);
goto again;
}
@@ -2186,7 +2184,7 @@ void mem_cgroup_update_page_stat(struct page *page,
pc = lookup_page_cgroup(page);
memcg = pc->mem_cgroup;
- if (unlikely(!memcg || !PageCgroupUsed(pc)))
+ if (unlikely(!memcg))
return;
this_cpu_add(memcg->stat->count[idx], val);
@@ -2525,9 +2523,10 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
VM_BUG_ON_PAGE(!PageLocked(page), page);
pc = lookup_page_cgroup(page);
- if (PageCgroupUsed(pc)) {
- memcg = pc->mem_cgroup;
- if (memcg && !css_tryget_online(&memcg->css))
+ memcg = pc->mem_cgroup;
+
+ if (memcg) {
+ if (!css_tryget_online(&memcg->css))
memcg = NULL;
} else if (PageSwapCache(page)) {
ent.val = page_private(page);
@@ -2578,7 +2577,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
struct page_cgroup *pc = lookup_page_cgroup(page);
int isolated;
- VM_BUG_ON_PAGE(PageCgroupUsed(pc), page);
+ VM_BUG_ON_PAGE(pc->mem_cgroup, page);
/*
* we don't need page_cgroup_lock about tail pages, becase they are not
* accessed by any other context at this point.
@@ -2593,7 +2592,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
/*
* Nobody should be changing or seriously looking at
- * pc->mem_cgroup and pc->flags at this point:
+ * pc->mem_cgroup at this point:
*
* - the page is uncharged
*
@@ -2606,7 +2605,6 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
* have the page locked
*/
pc->mem_cgroup = memcg;
- pc->flags = PCG_USED;
if (lrucare)
unlock_page_lru(page, isolated);
@@ -3120,37 +3118,22 @@ void __memcg_kmem_commit_charge(struct page *page, struct mem_cgroup *memcg,
memcg_uncharge_kmem(memcg, 1 << order);
return;
}
- /*
- * The page is freshly allocated and not visible to any
- * outside callers yet. Set up pc non-atomically.
- */
pc = lookup_page_cgroup(page);
pc->mem_cgroup = memcg;
- pc->flags = PCG_USED;
}
void __memcg_kmem_uncharge_pages(struct page *page, int order)
{
- struct mem_cgroup *memcg = NULL;
- struct page_cgroup *pc;
-
-
- pc = lookup_page_cgroup(page);
- if (!PageCgroupUsed(pc))
- return;
-
- memcg = pc->mem_cgroup;
- pc->flags = 0;
+ struct page_cgroup *pc = lookup_page_cgroup(page);
+ struct mem_cgroup *memcg = pc->mem_cgroup;
- /*
- * We trust that only if there is a memcg associated with the page, it
- * is a valid allocation
- */
if (!memcg)
return;
VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page);
+
memcg_uncharge_kmem(memcg, 1 << order);
+ pc->mem_cgroup = NULL;
}
#else
static inline void memcg_unregister_all_caches(struct mem_cgroup *memcg)
@@ -3168,21 +3151,16 @@ static inline void memcg_unregister_all_caches(struct mem_cgroup *memcg)
*/
void mem_cgroup_split_huge_fixup(struct page *head)
{
- struct page_cgroup *head_pc = lookup_page_cgroup(head);
- struct page_cgroup *pc;
- struct mem_cgroup *memcg;
+ struct page_cgroup *pc = lookup_page_cgroup(head);
int i;
if (mem_cgroup_disabled())
return;
- memcg = head_pc->mem_cgroup;
- for (i = 1; i < HPAGE_PMD_NR; i++) {
- pc = head_pc + i;
- pc->mem_cgroup = memcg;
- pc->flags = head_pc->flags;
- }
- __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
+ for (i = 1; i < HPAGE_PMD_NR; i++)
+ pc[i].mem_cgroup = pc[0].mem_cgroup;
+
+ __this_cpu_sub(pc[0].mem_cgroup->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
HPAGE_PMD_NR);
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
@@ -3232,7 +3210,7 @@ static int mem_cgroup_move_account(struct page *page,
goto out;
ret = -EINVAL;
- if (!PageCgroupUsed(pc) || pc->mem_cgroup != from)
+ if (pc->mem_cgroup != from)
goto out_unlock;
move_lock_mem_cgroup(from, &flags);
@@ -3342,7 +3320,7 @@ static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
* the first time, i.e. during boot or memory hotplug;
* or when mem_cgroup_disabled().
*/
- if (likely(pc) && PageCgroupUsed(pc))
+ if (likely(pc) && pc->mem_cgroup)
return pc;
return NULL;
}
@@ -3360,10 +3338,8 @@ void mem_cgroup_print_bad_page(struct page *page)
struct page_cgroup *pc;
pc = lookup_page_cgroup_used(page);
- if (pc) {
- pr_alert("pc:%p pc->flags:%lx pc->mem_cgroup:%p\n",
- pc, pc->flags, pc->mem_cgroup);
- }
+ if (pc)
+ pr_alert("pc:%p pc->mem_cgroup:%p\n", pc, pc->mem_cgroup);
}
#endif
@@ -5330,7 +5306,7 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
* mem_cgroup_move_account() checks the pc is valid or
* not under LRU exclusion.
*/
- if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
+ if (pc->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
if (target)
target->page = page;
@@ -5366,7 +5342,7 @@ static enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma,
if (!move_anon())
return ret;
pc = lookup_page_cgroup(page);
- if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
+ if (pc->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
if (target) {
get_page(page);
@@ -5810,18 +5786,17 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
return;
pc = lookup_page_cgroup(page);
+ memcg = pc->mem_cgroup;
/* Readahead page, never charged */
- if (!PageCgroupUsed(pc))
+ if (!memcg)
return;
- memcg = pc->mem_cgroup;
-
oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg));
VM_BUG_ON_PAGE(oldid, page);
mem_cgroup_swap_statistics(memcg, true);
- pc->flags = 0;
+ pc->mem_cgroup = NULL;
if (!mem_cgroup_is_root(memcg))
page_counter_uncharge(&memcg->memory, 1);
@@ -5895,7 +5870,7 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
* the page lock, which serializes swap cache removal, which
* in turn serializes uncharging.
*/
- if (PageCgroupUsed(pc))
+ if (pc->mem_cgroup)
goto out;
}
@@ -6057,13 +6032,13 @@ static void uncharge_list(struct list_head *page_list)
VM_BUG_ON_PAGE(page_count(page), page);
pc = lookup_page_cgroup(page);
- if (!PageCgroupUsed(pc))
+ if (!pc->mem_cgroup)
continue;
/*
* Nobody should be changing or seriously looking at
- * pc->mem_cgroup and pc->flags at this point, we have
- * fully exclusive access to the page.
+ * pc->mem_cgroup at this point, we have fully
+ * exclusive access to the page.
*/
if (memcg != pc->mem_cgroup) {
@@ -6086,7 +6061,7 @@ static void uncharge_list(struct list_head *page_list)
else
nr_file += nr_pages;
- pc->flags = 0;
+ pc->mem_cgroup = NULL;
pgpgout++;
} while (next != page_list);
@@ -6112,7 +6087,7 @@ void mem_cgroup_uncharge(struct page *page)
/* Don't touch page->lru of any random page, pre-check: */
pc = lookup_page_cgroup(page);
- if (!PageCgroupUsed(pc))
+ if (!pc->mem_cgroup)
return;
INIT_LIST_HEAD(&page->lru);
@@ -6148,6 +6123,7 @@ void mem_cgroup_uncharge_list(struct list_head *page_list)
void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
bool lrucare)
{
+ struct mem_cgroup *memcg;
struct page_cgroup *pc;
int isolated;
@@ -6164,7 +6140,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
/* Page cache replacement: new page already charged? */
pc = lookup_page_cgroup(newpage);
- if (PageCgroupUsed(pc))
+ if (pc->mem_cgroup)
return;
/*
@@ -6174,18 +6150,19 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
* reclaim just put back on the LRU but has not released yet.
*/
pc = lookup_page_cgroup(oldpage);
- if (!PageCgroupUsed(pc))
+ memcg = pc->mem_cgroup;
+ if (!memcg)
return;
if (lrucare)
lock_page_lru(oldpage, &isolated);
- pc->flags = 0;
+ pc->mem_cgroup = NULL;
if (lrucare)
unlock_page_lru(oldpage, isolated);
- commit_charge(newpage, pc->mem_cgroup, lrucare);
+ commit_charge(newpage, memcg, lrucare);
}
/*
--
2.1.2
--
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