Commit 4b3bde4c authored by Balbir Singh's avatar Balbir Singh Committed by Linus Torvalds
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memcg: remove the overhead associated with the root cgroup



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.

[akpm@linux-foundation.org: fix a few documentation glitches]
Signed-off-by: default avatarBalbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent be367d09
......@@ -179,6 +179,9 @@ The reclaim algorithm has not been modified for cgroups, except that
pages that are selected for reclaiming come from the per cgroup LRU
list.
NOTE: Reclaim does not work 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 any more.
# cat /cgroups/0/memory.limit_in_bytes
4194304
......
......@@ -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(struct page_cgroup *pc)\
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)
{
......
......@@ -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 mem_cgroup *root, void *data,
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 mem_cgroup *root, void *data,
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 page *page, enum lru_list lru)
* 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) || mem_cgroup_is_root(pc->mem_cgroup))
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 *page, enum lru_list lru)
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 *page, enum lru_list lru)
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_commit_swapcache(struct page *page)
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(struct mem_cgroup *mem,
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);
......@@ -2083,6 +2103,10 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
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)
......@@ -2549,6 +2573,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
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;
......@@ -2577,6 +2602,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
return &mem->css;
free_out:
__mem_cgroup_free(mem);
root_mem_cgroup = NULL;
return ERR_PTR(error);
}
......
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