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Message-Id: <20111206191746.58f9f736.kamezawa.hiroyu@jp.fujitsu.com>
Date: Tue, 6 Dec 2011 19:17:46 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Miklos Szeredi <mszeredi@...e.cz>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>, cgroups@...r.kernel.org,
"hannes@...xchg.org" <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>
Subject: [RFC][PATCH 4/4] memcg: new LRU rule
Not measured performance yet, sorry.
==
>From 3f2539d695084eb8b83ec08347587b1e1f2efa9a Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Date: Tue, 6 Dec 2011 19:09:06 +0900
Subject: [PATCH 4/4] memcg: new LRU rule
Now, at LRU handling, memory cgroup needs to do complicated works
to see valid pc->mem_cgroup, which may be overwritten.
This patch is for relaxing the protocol. This patch guarantees
- when pc->mem_cgroup is overwritten, page must not be on LRU.
By this, LRU routine can believe pc->mem_cgroup and don't need to
check bits on pc->flags. This new rule may adds small
overheads to swap-in but, in most case, lru handling gets faster
and reduce overheads.
After this patch, PCG_ACCT_LRU bit is obsolete and removed.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
include/linux/page_cgroup.h | 8 ----
mm/memcontrol.c | 81 +++++++++++-------------------------------
2 files changed, 21 insertions(+), 68 deletions(-)
diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index aaa60da..2cddacf 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -10,8 +10,6 @@ enum {
/* flags for mem_cgroup and file and I/O status */
PCG_MOVE_LOCK, /* For race between move_account v.s. following bits */
PCG_FILE_MAPPED, /* page is accounted as "mapped" */
- /* No lock in page_cgroup */
- PCG_ACCT_LRU, /* page has been accounted for (under lru_lock) */
__NR_PCG_FLAGS,
};
@@ -75,12 +73,6 @@ TESTPCGFLAG(Used, USED)
CLEARPCGFLAG(Used, USED)
SETPCGFLAG(Used, USED)
-SETPCGFLAG(AcctLRU, ACCT_LRU)
-CLEARPCGFLAG(AcctLRU, ACCT_LRU)
-TESTPCGFLAG(AcctLRU, ACCT_LRU)
-TESTCLEARPCGFLAG(AcctLRU, ACCT_LRU)
-
-
SETPCGFLAG(FileMapped, FILE_MAPPED)
CLEARPCGFLAG(FileMapped, FILE_MAPPED)
TESTPCGFLAG(FileMapped, FILE_MAPPED)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b8706d8..0814cda 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -974,30 +974,7 @@ struct lruvec *mem_cgroup_lru_add_list(struct zone *zone, struct page *page,
return &zone->lruvec;
pc = lookup_page_cgroup(page);
- VM_BUG_ON(PageCgroupAcctLRU(pc));
- /*
- * putback: charge:
- * SetPageLRU SetPageCgroupUsed
- * smp_mb smp_mb
- * PageCgroupUsed && add to memcg LRU PageLRU && add to memcg LRU
- *
- * Ensure that one of the two sides adds the page to the memcg
- * LRU during a race.
- */
- smp_mb();
- /*
- * If the page is uncharged, it may be freed soon, but it
- * could also be swap cache (readahead, swapoff) that needs to
- * be reclaimable in the future. root_mem_cgroup will babysit
- * it for the time being.
- */
- if (PageCgroupUsed(pc)) {
- /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
- smp_rmb();
- memcg = pc->mem_cgroup;
- SetPageCgroupAcctLRU(pc);
- } else
- memcg = root_mem_cgroup;
+ memcg = pc->mem_cgroup;
mz = page_cgroup_zoneinfo(memcg, page);
/* compound_order() is stabilized through lru_lock */
MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page);
@@ -1024,18 +1001,7 @@ void mem_cgroup_lru_del_list(struct page *page, enum lru_list lru)
return;
pc = lookup_page_cgroup(page);
- /*
- * root_mem_cgroup babysits uncharged LRU pages, but
- * PageCgroupUsed is cleared when the page is about to get
- * freed. PageCgroupAcctLRU remembers whether the
- * LRU-accounting happened against pc->mem_cgroup or
- * root_mem_cgroup.
- */
- if (TestClearPageCgroupAcctLRU(pc)) {
- VM_BUG_ON(!pc->mem_cgroup);
- memcg = pc->mem_cgroup;
- } else
- memcg = root_mem_cgroup;
+ memcg = pc->mem_cgroup;
mz = page_cgroup_zoneinfo(memcg, page);
/* huge page split is done under lru_lock. so, we have no races. */
MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
@@ -2377,6 +2343,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), nr_pages);
unlock_page_cgroup(pc);
+ WARN_ON_ONCE(PageLRU(page));
/*
* "charge_statistics" updated event counter. Then, check it.
* Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
@@ -2388,7 +2355,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define PCGF_NOCOPY_AT_SPLIT ((1 << PCG_LOCK) | (1 << PCG_MOVE_LOCK) |\
- (1 << PCG_ACCT_LRU) | (1 << PCG_MIGRATION))
+ (1 << PCG_MIGRATION))
/*
* Because tail pages are not marked as "used", set it. We're under
* zone->lru_lock, 'splitting on pmd' and compound_lock.
@@ -2399,6 +2366,8 @@ 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_per_zone *mz;
+ enum lru_list lru;
int i;
if (mem_cgroup_disabled())
@@ -2414,16 +2383,12 @@ void mem_cgroup_split_huge_fixup(struct page *head)
pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
}
- if (PageCgroupAcctLRU(head_pc)) {
- enum lru_list lru;
- struct mem_cgroup_per_zone *mz;
- /*
- * We hold lru_lock, then, reduce counter directly.
- */
- lru = page_lru(head);
- mz = page_cgroup_zoneinfo(head_pc->mem_cgroup, head);
- MEM_CGROUP_ZSTAT(mz, lru) -= HPAGE_PMD_NR - 1;
- }
+ /*
+ * We hold lru_lock, then, reduce counter directly.
+ */
+ lru = page_lru(head);
+ mz = page_cgroup_zoneinfo(head_pc->mem_cgroup, head);
+ MEM_CGROUP_ZSTAT(mz, lru) -= HPAGE_PMD_NR - 1;
}
#endif
@@ -2617,17 +2582,23 @@ __mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *memcg,
struct page_cgroup *pc = lookup_page_cgroup(page);
struct zone *zone = page_zone(page);
unsigned long flags;
+ bool removed = false;
/*
* In some case, SwapCache, FUSE(splice_buf->radixtree), the page
* is already on LRU. It means the page may on some other page_cgroup's
* LRU. Take care of it.
*/
spin_lock_irqsave(&zone->lru_lock, flags);
- if (PageLRU(page))
+ if (PageLRU(page)) {
del_page_from_lru_list(zone, page, page_lru(page));
+ ClearPageLRU(page);
+ removed = true;
+ }
__mem_cgroup_commit_charge(memcg, page, 1, pc, ctype);
- if (PageLRU(page))
+ if (removed) {
+ SetPageLRU(page);
add_page_to_lru_list(zone, page, page_lru(page));
+ }
spin_unlock_irqrestore(&zone->lru_lock, flags);
return;
}
@@ -3243,9 +3214,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
{
struct mem_cgroup *memcg;
struct page_cgroup *pc;
- struct zone *zone;
enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
- unsigned long flags;
pc = lookup_page_cgroup(oldpage);
/* fix accounting on old pages */
@@ -3258,20 +3227,12 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
if (PageSwapBacked(oldpage))
type = MEM_CGROUP_CHARGE_TYPE_SHMEM;
- zone = page_zone(newpage);
- pc = lookup_page_cgroup(newpage);
/*
* Even if newpage->mapping was NULL before starting replacement,
* the newpage may be on LRU(or pagevec for LRU) already. We lock
* LRU while we overwrite pc->mem_cgroup.
*/
- spin_lock_irqsave(&zone->lru_lock, flags);
- if (PageLRU(newpage))
- del_page_from_lru_list(zone, newpage, page_lru(newpage));
- __mem_cgroup_commit_charge(memcg, newpage, 1, pc, type);
- if (PageLRU(newpage))
- add_page_to_lru_list(zone, newpage, page_lru(newpage));
- spin_unlock_irqrestore(&zone->lru_lock, flags);
+ __mem_cgroup_commit_charge_lrucare(newpage, memcg, type);
}
#ifdef CONFIG_DEBUG_VM
--
1.7.4.1
--
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