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 commit 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.
[akpm@linux-foundation.org: remove unneeded initialization of `memcg', per Michal]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3dfb56a..09fece0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1284,14 +1284,12 @@
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;
@@ -2151,7 +2149,7 @@
pc = lookup_page_cgroup(page);
again:
memcg = pc->mem_cgroup;
- if (unlikely(!memcg || !PageCgroupUsed(pc)))
+ if (unlikely(!memcg))
return NULL;
*locked = false;
@@ -2159,7 +2157,7 @@
return memcg;
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;
}
@@ -2525,7 +2523,7 @@
*/
struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
{
- struct mem_cgroup *memcg = NULL;
+ struct mem_cgroup *memcg;
struct page_cgroup *pc;
unsigned short id;
swp_entry_t ent;
@@ -2533,9 +2531,10 @@
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);
@@ -2586,7 +2585,7 @@
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.
@@ -2601,7 +2600,7 @@
/*
* 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
*
@@ -2614,7 +2613,6 @@
* have the page locked
*/
pc->mem_cgroup = memcg;
- pc->flags = PCG_USED;
if (lrucare)
unlock_page_lru(page, isolated);
@@ -3126,37 +3124,22 @@
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;
+ struct page_cgroup *pc = lookup_page_cgroup(page);
+ struct mem_cgroup *memcg = pc->mem_cgroup;
-
- pc = lookup_page_cgroup(page);
- if (!PageCgroupUsed(pc))
- return;
-
- memcg = pc->mem_cgroup;
- pc->flags = 0;
-
- /*
- * 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)
@@ -3174,23 +3157,16 @@
*/
void mem_cgroup_split_huge_fixup(struct page *head)
{
- struct page_cgroup *head_pc;
- struct page_cgroup *pc;
- struct mem_cgroup *memcg;
+ struct page_cgroup *pc = lookup_page_cgroup(head);
int i;
if (mem_cgroup_disabled())
return;
- head_pc = lookup_page_cgroup(head);
+ for (i = 1; i < HPAGE_PMD_NR; i++)
+ pc[i].mem_cgroup = pc[0].mem_cgroup;
- 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],
+ __this_cpu_sub(pc[0].mem_cgroup->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
HPAGE_PMD_NR);
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
@@ -3240,7 +3216,7 @@
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);
@@ -3350,7 +3326,7 @@
* 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;
}
@@ -3368,10 +3344,8 @@
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
@@ -5308,7 +5282,7 @@
* 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;
@@ -5344,7 +5318,7 @@
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);
@@ -5788,18 +5762,17 @@
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);
@@ -5874,7 +5847,7 @@
* the page lock, which serializes swap cache removal, which
* in turn serializes uncharging.
*/
- if (PageCgroupUsed(pc))
+ if (pc->mem_cgroup)
goto out;
}
@@ -6036,13 +6009,13 @@
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) {
@@ -6065,7 +6038,7 @@
else
nr_file += nr_pages;
- pc->flags = 0;
+ pc->mem_cgroup = NULL;
pgpgout++;
} while (next != page_list);
@@ -6091,7 +6064,7 @@
/* 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);
@@ -6127,6 +6100,7 @@
void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
bool lrucare)
{
+ struct mem_cgroup *memcg;
struct page_cgroup *pc;
int isolated;
@@ -6143,7 +6117,7 @@
/* Page cache replacement: new page already charged? */
pc = lookup_page_cgroup(newpage);
- if (PageCgroupUsed(pc))
+ if (pc->mem_cgroup)
return;
/*
@@ -6153,18 +6127,19 @@
* 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);
}
/*