mm: embed the memcg pointer directly into struct page
Memory cgroups used to have 5 per-page pointers. To allow users to
disable that amount of overhead during runtime, those pointers were
allocated in a separate array, with a translation layer between them and
struct page.
There is now only one page pointer remaining: the memcg pointer, that
indicates which cgroup the page is associated with when charged. The
complexity of runtime allocation and the runtime translation overhead is
no longer justified to save that *potential* 0.19% of memory. With
CONFIG_SLUB, page->mem_cgroup actually sits in the doubleword padding
after the page->private member and doesn't even increase struct page,
and then this patch actually saves space. Remaining users that care can
still compile their kernels without CONFIG_MEMCG.
text data bss dec hex filename
8828345 1725264 983040 11536649 b00909 vmlinux.old
8827425 1725264 966656 11519345 afc571 vmlinux.new
[mhocko@suse.cz: update Documentation/cgroups/memory.txt]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Konstantin Khlebnikov <koct9i@gmail.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 78cb3b0..b864067 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1274,7 +1274,6 @@
{
struct mem_cgroup_per_zone *mz;
struct mem_cgroup *memcg;
- struct page_cgroup *pc;
struct lruvec *lruvec;
if (mem_cgroup_disabled()) {
@@ -1282,8 +1281,7 @@
goto out;
}
- pc = lookup_page_cgroup(page);
- memcg = pc->mem_cgroup;
+ memcg = page->mem_cgroup;
/*
* Swapcache readahead pages are added to the LRU - and
* possibly migrated - before they are charged.
@@ -2020,16 +2018,13 @@
unsigned long *flags)
{
struct mem_cgroup *memcg;
- struct page_cgroup *pc;
rcu_read_lock();
if (mem_cgroup_disabled())
return NULL;
-
- pc = lookup_page_cgroup(page);
again:
- memcg = pc->mem_cgroup;
+ memcg = page->mem_cgroup;
if (unlikely(!memcg))
return NULL;
@@ -2038,7 +2033,7 @@
return memcg;
spin_lock_irqsave(&memcg->move_lock, *flags);
- if (memcg != pc->mem_cgroup) {
+ if (memcg != page->mem_cgroup) {
spin_unlock_irqrestore(&memcg->move_lock, *flags);
goto again;
}
@@ -2405,15 +2400,12 @@
struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
{
struct mem_cgroup *memcg;
- struct page_cgroup *pc;
unsigned short id;
swp_entry_t ent;
VM_BUG_ON_PAGE(!PageLocked(page), page);
- pc = lookup_page_cgroup(page);
- memcg = pc->mem_cgroup;
-
+ memcg = page->mem_cgroup;
if (memcg) {
if (!css_tryget_online(&memcg->css))
memcg = NULL;
@@ -2463,10 +2455,9 @@
static void commit_charge(struct page *page, struct mem_cgroup *memcg,
bool lrucare)
{
- struct page_cgroup *pc = lookup_page_cgroup(page);
int isolated;
- VM_BUG_ON_PAGE(pc->mem_cgroup, page);
+ VM_BUG_ON_PAGE(page->mem_cgroup, page);
/*
* In some cases, SwapCache and FUSE(splice_buf->radixtree), the page
@@ -2477,7 +2468,7 @@
/*
* Nobody should be changing or seriously looking at
- * pc->mem_cgroup at this point:
+ * page->mem_cgroup at this point:
*
* - the page is uncharged
*
@@ -2489,7 +2480,7 @@
* - a page cache insertion, a swapin fault, or a migration
* have the page locked
*/
- pc->mem_cgroup = memcg;
+ page->mem_cgroup = memcg;
if (lrucare)
unlock_page_lru(page, isolated);
@@ -2972,8 +2963,6 @@
void __memcg_kmem_commit_charge(struct page *page, struct mem_cgroup *memcg,
int order)
{
- struct page_cgroup *pc;
-
VM_BUG_ON(mem_cgroup_is_root(memcg));
/* The page allocation failed. Revert */
@@ -2981,14 +2970,12 @@
memcg_uncharge_kmem(memcg, 1 << order);
return;
}
- pc = lookup_page_cgroup(page);
- pc->mem_cgroup = memcg;
+ page->mem_cgroup = memcg;
}
void __memcg_kmem_uncharge_pages(struct page *page, int order)
{
- struct page_cgroup *pc = lookup_page_cgroup(page);
- struct mem_cgroup *memcg = pc->mem_cgroup;
+ struct mem_cgroup *memcg = page->mem_cgroup;
if (!memcg)
return;
@@ -2996,7 +2983,7 @@
VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page);
memcg_uncharge_kmem(memcg, 1 << order);
- pc->mem_cgroup = NULL;
+ page->mem_cgroup = NULL;
}
#else
static inline void memcg_unregister_all_caches(struct mem_cgroup *memcg)
@@ -3014,16 +3001,15 @@
*/
void mem_cgroup_split_huge_fixup(struct page *head)
{
- struct page_cgroup *pc = lookup_page_cgroup(head);
int i;
if (mem_cgroup_disabled())
return;
for (i = 1; i < HPAGE_PMD_NR; i++)
- pc[i].mem_cgroup = pc[0].mem_cgroup;
+ head[i].mem_cgroup = head->mem_cgroup;
- __this_cpu_sub(pc[0].mem_cgroup->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
+ __this_cpu_sub(head->mem_cgroup->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
HPAGE_PMD_NR);
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
@@ -3032,7 +3018,6 @@
* mem_cgroup_move_account - move account of the page
* @page: the page
* @nr_pages: number of regular pages (>1 for huge pages)
- * @pc: page_cgroup of the page.
* @from: mem_cgroup which the page is moved from.
* @to: mem_cgroup which the page is moved to. @from != @to.
*
@@ -3045,7 +3030,6 @@
*/
static int mem_cgroup_move_account(struct page *page,
unsigned int nr_pages,
- struct page_cgroup *pc,
struct mem_cgroup *from,
struct mem_cgroup *to)
{
@@ -3065,7 +3049,7 @@
goto out;
/*
- * Prevent mem_cgroup_migrate() from looking at pc->mem_cgroup
+ * Prevent mem_cgroup_migrate() from looking at page->mem_cgroup
* of its source page while we change it: page migration takes
* both pages off the LRU, but page cache replacement doesn't.
*/
@@ -3073,7 +3057,7 @@
goto out;
ret = -EINVAL;
- if (pc->mem_cgroup != from)
+ if (page->mem_cgroup != from)
goto out_unlock;
spin_lock_irqsave(&from->move_lock, flags);
@@ -3093,13 +3077,13 @@
}
/*
- * It is safe to change pc->mem_cgroup here because the page
+ * It is safe to change page->mem_cgroup here because the page
* is referenced, charged, and isolated - we can't race with
* uncharging, charging, migration, or LRU putback.
*/
/* caller should have done css_get */
- pc->mem_cgroup = to;
+ page->mem_cgroup = to;
spin_unlock_irqrestore(&from->move_lock, flags);
ret = 0;
@@ -3174,36 +3158,17 @@
#endif
#ifdef CONFIG_DEBUG_VM
-static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
-{
- struct page_cgroup *pc;
-
- pc = lookup_page_cgroup(page);
- /*
- * Can be NULL while feeding pages into the page allocator for
- * the first time, i.e. during boot or memory hotplug;
- * or when mem_cgroup_disabled().
- */
- if (likely(pc) && pc->mem_cgroup)
- return pc;
- return NULL;
-}
-
bool mem_cgroup_bad_page_check(struct page *page)
{
if (mem_cgroup_disabled())
return false;
- return lookup_page_cgroup_used(page) != NULL;
+ return page->mem_cgroup != NULL;
}
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->mem_cgroup:%p\n", pc, pc->mem_cgroup);
+ pr_alert("page->mem_cgroup:%p\n", page->mem_cgroup);
}
#endif
@@ -5123,7 +5088,6 @@
unsigned long addr, pte_t ptent, union mc_target *target)
{
struct page *page = NULL;
- struct page_cgroup *pc;
enum mc_target_type ret = MC_TARGET_NONE;
swp_entry_t ent = { .val = 0 };
@@ -5137,13 +5101,12 @@
if (!page && !ent.val)
return ret;
if (page) {
- pc = lookup_page_cgroup(page);
/*
* Do only loose check w/o serialization.
- * mem_cgroup_move_account() checks the pc is valid or
+ * mem_cgroup_move_account() checks the page is valid or
* not under LRU exclusion.
*/
- if (pc->mem_cgroup == mc.from) {
+ if (page->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
if (target)
target->page = page;
@@ -5171,15 +5134,13 @@
unsigned long addr, pmd_t pmd, union mc_target *target)
{
struct page *page = NULL;
- struct page_cgroup *pc;
enum mc_target_type ret = MC_TARGET_NONE;
page = pmd_page(pmd);
VM_BUG_ON_PAGE(!page || !PageHead(page), page);
if (!move_anon())
return ret;
- pc = lookup_page_cgroup(page);
- if (pc->mem_cgroup == mc.from) {
+ if (page->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
if (target) {
get_page(page);
@@ -5378,7 +5339,6 @@
enum mc_target_type target_type;
union mc_target target;
struct page *page;
- struct page_cgroup *pc;
/*
* We don't take compound_lock() here but no race with splitting thp
@@ -5399,9 +5359,8 @@
if (target_type == MC_TARGET_PAGE) {
page = target.page;
if (!isolate_lru_page(page)) {
- pc = lookup_page_cgroup(page);
if (!mem_cgroup_move_account(page, HPAGE_PMD_NR,
- pc, mc.from, mc.to)) {
+ mc.from, mc.to)) {
mc.precharge -= HPAGE_PMD_NR;
mc.moved_charge += HPAGE_PMD_NR;
}
@@ -5429,9 +5388,7 @@
page = target.page;
if (isolate_lru_page(page))
goto put;
- pc = lookup_page_cgroup(page);
- if (!mem_cgroup_move_account(page, 1, pc,
- mc.from, mc.to)) {
+ if (!mem_cgroup_move_account(page, 1, mc.from, mc.to)) {
mc.precharge--;
/* we uncharge from mc.from later. */
mc.moved_charge++;
@@ -5619,7 +5576,6 @@
void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
{
struct mem_cgroup *memcg;
- struct page_cgroup *pc;
unsigned short oldid;
VM_BUG_ON_PAGE(PageLRU(page), page);
@@ -5628,8 +5584,7 @@
if (!do_swap_account)
return;
- pc = lookup_page_cgroup(page);
- memcg = pc->mem_cgroup;
+ memcg = page->mem_cgroup;
/* Readahead page, never charged */
if (!memcg)
@@ -5639,7 +5594,7 @@
VM_BUG_ON_PAGE(oldid, page);
mem_cgroup_swap_statistics(memcg, true);
- pc->mem_cgroup = NULL;
+ page->mem_cgroup = NULL;
if (!mem_cgroup_is_root(memcg))
page_counter_uncharge(&memcg->memory, 1);
@@ -5706,7 +5661,6 @@
goto out;
if (PageSwapCache(page)) {
- struct page_cgroup *pc = lookup_page_cgroup(page);
/*
* Every swap fault against a single page tries to charge the
* page, bail as early as possible. shmem_unuse() encounters
@@ -5714,7 +5668,7 @@
* the page lock, which serializes swap cache removal, which
* in turn serializes uncharging.
*/
- if (pc->mem_cgroup)
+ if (page->mem_cgroup)
goto out;
}
@@ -5867,7 +5821,6 @@
next = page_list->next;
do {
unsigned int nr_pages = 1;
- struct page_cgroup *pc;
page = list_entry(next, struct page, lru);
next = page->lru.next;
@@ -5875,23 +5828,22 @@
VM_BUG_ON_PAGE(PageLRU(page), page);
VM_BUG_ON_PAGE(page_count(page), page);
- pc = lookup_page_cgroup(page);
- if (!pc->mem_cgroup)
+ if (!page->mem_cgroup)
continue;
/*
* Nobody should be changing or seriously looking at
- * pc->mem_cgroup at this point, we have fully
+ * page->mem_cgroup at this point, we have fully
* exclusive access to the page.
*/
- if (memcg != pc->mem_cgroup) {
+ if (memcg != page->mem_cgroup) {
if (memcg) {
uncharge_batch(memcg, pgpgout, nr_anon, nr_file,
nr_huge, page);
pgpgout = nr_anon = nr_file = nr_huge = 0;
}
- memcg = pc->mem_cgroup;
+ memcg = page->mem_cgroup;
}
if (PageTransHuge(page)) {
@@ -5905,7 +5857,7 @@
else
nr_file += nr_pages;
- pc->mem_cgroup = NULL;
+ page->mem_cgroup = NULL;
pgpgout++;
} while (next != page_list);
@@ -5924,14 +5876,11 @@
*/
void mem_cgroup_uncharge(struct page *page)
{
- struct page_cgroup *pc;
-
if (mem_cgroup_disabled())
return;
/* Don't touch page->lru of any random page, pre-check: */
- pc = lookup_page_cgroup(page);
- if (!pc->mem_cgroup)
+ if (!page->mem_cgroup)
return;
INIT_LIST_HEAD(&page->lru);
@@ -5968,7 +5917,6 @@
bool lrucare)
{
struct mem_cgroup *memcg;
- struct page_cgroup *pc;
int isolated;
VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
@@ -5983,8 +5931,7 @@
return;
/* Page cache replacement: new page already charged? */
- pc = lookup_page_cgroup(newpage);
- if (pc->mem_cgroup)
+ if (newpage->mem_cgroup)
return;
/*
@@ -5993,15 +5940,14 @@
* uncharged page when the PFN walker finds a page that
* reclaim just put back on the LRU but has not released yet.
*/
- pc = lookup_page_cgroup(oldpage);
- memcg = pc->mem_cgroup;
+ memcg = oldpage->mem_cgroup;
if (!memcg)
return;
if (lrucare)
lock_page_lru(oldpage, &isolated);
- pc->mem_cgroup = NULL;
+ oldpage->mem_cgroup = NULL;
if (lrucare)
unlock_page_lru(oldpage, isolated);