The patch titled
memcg: remove the overhead associated with the root cgroup
has been added to the -mm tree. Its filename is
memcg-remove-the-overhead-associated-with-the-root-cgroup.patch
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------------------------------------------------------
Subject: memcg: remove the overhead associated with the root cgroup
From: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Change the memory cgroup to remove the overhead associated with accounting
all pages in the root cgroup. As a side-effect, we can no longer set a
memory hard limit in the root cgroup.
A new flag to track whether the page has been accounted or not has been
added as well. Flags are now set atomically for page_cgroup,
pcg_default_flags is now obsolete and removed.
Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/cgroups/memory.txt | 4 ++
include/linux/page_cgroup.h | 13 ++++++
mm/memcontrol.c | 54 +++++++++++++++++++++--------
3 files changed, 57 insertions(+), 14 deletions(-)
diff -puN Documentation/cgroups/memory.txt~memcg-remove-the-overhead-associated-with-the-root-cgroup Documentation/cgroups/memory.txt
--- a/Documentation/cgroups/memory.txt~memcg-remove-the-overhead-associated-with-the-root-cgroup
+++ a/Documentation/cgroups/memory.txt
@@ -179,6 +179,9 @@ The reclaim algorithm has not been modif
pages that are selected for reclaiming come from the per cgroup LRU
list.
+NOTE: Reclaim does not works for the root cgroup, since we cannot
+set any limits on the root cgroup
+
2. Locking
The memory controller uses the following hierarchy
@@ -210,6 +213,7 @@ We can alter the memory limit:
NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
mega or gigabytes.
NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited).
+NOTE: We cannot set limits on the root cgroup anymore.
# cat /cgroups/0/memory.limit_in_bytes
4194304
diff -puN include/linux/page_cgroup.h~memcg-remove-the-overhead-associated-with-the-root-cgroup include/linux/page_cgroup.h
--- a/include/linux/page_cgroup.h~memcg-remove-the-overhead-associated-with-the-root-cgroup
+++ a/include/linux/page_cgroup.h
@@ -38,6 +38,7 @@ enum {
PCG_LOCK, /* page cgroup is locked */
PCG_CACHE, /* charged as cache */
PCG_USED, /* this object is in use. */
+ PCG_ACCT_LRU, /* page has been accounted for */
};
#define TESTPCGFLAG(uname, lname) \
@@ -52,11 +53,23 @@ static inline void SetPageCgroup##uname(
static inline void ClearPageCgroup##uname(struct page_cgroup *pc) \
{ clear_bit(PCG_##lname, &pc->flags); }
+#define TESTCLEARPCGFLAG(uname, lname) \
+static inline int TestClearPageCgroup##uname(struct page_cgroup *pc) \
+ { return test_and_clear_bit(PCG_##lname, &pc->flags); }
+
/* Cache flag is set only once (at allocation) */
TESTPCGFLAG(Cache, CACHE)
+CLEARPCGFLAG(Cache, CACHE)
+SETPCGFLAG(Cache, CACHE)
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)
static inline int page_cgroup_nid(struct page_cgroup *pc)
{
diff -puN mm/memcontrol.c~memcg-remove-the-overhead-associated-with-the-root-cgroup mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-remove-the-overhead-associated-with-the-root-cgroup
+++ a/mm/memcontrol.c
@@ -43,6 +43,7 @@
struct cgroup_subsys mem_cgroup_subsys __read_mostly;
#define MEM_CGROUP_RECLAIM_RETRIES 5
+struct mem_cgroup *root_mem_cgroup __read_mostly;
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
/* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
@@ -200,13 +201,8 @@ enum charge_type {
#define PCGF_CACHE (1UL << PCG_CACHE)
#define PCGF_USED (1UL << PCG_USED)
#define PCGF_LOCK (1UL << PCG_LOCK)
-static const unsigned long
-pcg_default_flags[NR_CHARGE_TYPE] = {
- PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* File Cache */
- PCGF_USED | PCGF_LOCK, /* Anon */
- PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* Shmem */
- 0, /* FORCE */
-};
+/* Not used, but added here for completeness */
+#define PCGF_ACCT (1UL << PCG_ACCT)
/* for encoding cft->private value on file */
#define _MEM (0)
@@ -354,6 +350,11 @@ static int mem_cgroup_walk_tree(struct m
return ret;
}
+static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
+{
+ return (mem == root_mem_cgroup);
+}
+
/*
* Following LRU functions are allowed to be used without PCG_LOCK.
* Operations are called by routine of global LRU independently from memcg.
@@ -371,22 +372,24 @@ static int mem_cgroup_walk_tree(struct m
void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
{
struct page_cgroup *pc;
- struct mem_cgroup *mem;
struct mem_cgroup_per_zone *mz;
if (mem_cgroup_disabled())
return;
pc = lookup_page_cgroup(page);
/* can happen while we handle swapcache. */
- if (list_empty(&pc->lru) || !pc->mem_cgroup)
+ if (!TestClearPageCgroupAcctLRU(pc))
return;
+ VM_BUG_ON(!pc->mem_cgroup);
/*
* We don't check PCG_USED bit. It's cleared when the "page" is finally
* removed from global LRU.
*/
mz = page_cgroup_zoneinfo(pc);
- mem = pc->mem_cgroup;
MEM_CGROUP_ZSTAT(mz, lru) -= 1;
+ if (mem_cgroup_is_root(pc->mem_cgroup))
+ return;
+ VM_BUG_ON(list_empty(&pc->lru));
list_del_init(&pc->lru);
return;
}
@@ -410,8 +413,8 @@ void mem_cgroup_rotate_lru_list(struct p
* For making pc->mem_cgroup visible, insert smp_rmb() here.
*/
smp_rmb();
- /* unused page is not rotated. */
- if (!PageCgroupUsed(pc))
+ /* unused or root page is not rotated. */
+ if (!PageCgroupUsed(pc) || PageCgroupAcctLRU(pc))
return;
mz = page_cgroup_zoneinfo(pc);
list_move(&pc->lru, &mz->lists[lru]);
@@ -425,6 +428,7 @@ void mem_cgroup_add_lru_list(struct page
if (mem_cgroup_disabled())
return;
pc = lookup_page_cgroup(page);
+ VM_BUG_ON(PageCgroupAcctLRU(pc));
/*
* Used bit is set without atomic ops but after smp_wmb().
* For making pc->mem_cgroup visible, insert smp_rmb() here.
@@ -435,6 +439,9 @@ void mem_cgroup_add_lru_list(struct page
mz = page_cgroup_zoneinfo(pc);
MEM_CGROUP_ZSTAT(mz, lru) += 1;
+ SetPageCgroupAcctLRU(pc);
+ if (mem_cgroup_is_root(pc->mem_cgroup))
+ return;
list_add(&pc->lru, &mz->lists[lru]);
}
@@ -469,7 +476,7 @@ static void mem_cgroup_lru_add_after_com
spin_lock_irqsave(&zone->lru_lock, flags);
/* link when the page is linked to LRU but page_cgroup isn't */
- if (PageLRU(page) && list_empty(&pc->lru))
+ if (PageLRU(page) && !PageCgroupAcctLRU(pc))
mem_cgroup_add_lru_list(page, page_lru(page));
spin_unlock_irqrestore(&zone->lru_lock, flags);
}
@@ -1125,9 +1132,22 @@ static void __mem_cgroup_commit_charge(s
css_put(&mem->css);
return;
}
+
pc->mem_cgroup = mem;
smp_wmb();
- pc->flags = pcg_default_flags[ctype];
+ switch (ctype) {
+ case MEM_CGROUP_CHARGE_TYPE_CACHE:
+ case MEM_CGROUP_CHARGE_TYPE_SHMEM:
+ SetPageCgroupCache(pc);
+ SetPageCgroupUsed(pc);
+ break;
+ case MEM_CGROUP_CHARGE_TYPE_MAPPED:
+ ClearPageCgroupCache(pc);
+ SetPageCgroupUsed(pc);
+ break;
+ default:
+ break;
+ }
mem_cgroup_charge_statistics(mem, pc, true);
@@ -2066,6 +2086,10 @@ static int mem_cgroup_write(struct cgrou
name = MEMFILE_ATTR(cft->private);
switch (name) {
case RES_LIMIT:
+ if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
+ ret = -EINVAL;
+ break;
+ }
/* This function does all necessary parse...reuse it */
ret = res_counter_memparse_write_strategy(buffer, &val);
if (ret)
@@ -2532,6 +2556,7 @@ mem_cgroup_create(struct cgroup_subsys *
if (cont->parent == NULL) {
enable_swap_cgroup();
parent = NULL;
+ root_mem_cgroup = mem;
} else {
parent = mem_cgroup_from_cont(cont->parent);
mem->use_hierarchy = parent->use_hierarchy;
@@ -2560,6 +2585,7 @@ mem_cgroup_create(struct cgroup_subsys *
return &mem->css;
free_out:
__mem_cgroup_free(mem);
+ root_mem_cgroup = NULL;
return ERR_PTR(error);
}
_
Patches currently in -mm which might be from balbir@xxxxxxxxxxxxxxxxxx are
origin.patch
linux-next.patch
memcg-remove-the-overhead-associated-with-the-root-cgroup.patch
memcg-remove-the-overhead-associated-with-the-root-cgroup-fix.patch
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