[RFC] Low overhead patches for the memory cgroup controller (v2)
From: Balbir Singh
Date: Fri May 15 2009 - 11:18:43 EST
Feature: Remove the overhead associated with the root cgroup
From: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
This patch changes the memory cgroup and removes the overhead associated
with LRU maintenance of 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 is used to track page_cgroup associated with the root cgroup
pages. A new flag to track whether the page has been accounted or not
has been added as well.
Review comments higly appreciated
Tests
1. Tested with allocate, touch and limit test case for a non-root cgroup
2. For the root cgroup tested performance impact with reaim
+patch mmtom-08-may-2009
AIM9 1362.93 1338.17
Dbase 17457.75 16021.58
New Dbase 18070.18 16518.54
Shared 9681.85 8882.11
Compute 16197.79 15226.13
3. Tested accounting in root cgroup to make sure it looks sane and
correct.
Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
---
include/linux/page_cgroup.h | 10 ++++++++++
mm/memcontrol.c | 29 ++++++++++++++++++++++++++---
mm/page_cgroup.c | 1 -
3 files changed, 36 insertions(+), 4 deletions(-)
diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index 7339c7b..8b85752 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -26,6 +26,8 @@ enum {
PCG_LOCK, /* page cgroup is locked */
PCG_CACHE, /* charged as cache */
PCG_USED, /* this object is in use. */
+ PCG_ROOT, /* page belongs to root cgroup */
+ PCG_ACCT, /* page has been accounted for */
};
#define TESTPCGFLAG(uname, lname) \
@@ -46,6 +48,14 @@ TESTPCGFLAG(Cache, CACHE)
TESTPCGFLAG(Used, USED)
CLEARPCGFLAG(Used, USED)
+SETPCGFLAG(Root, ROOT)
+CLEARPCGFLAG(Root, ROOT)
+TESTPCGFLAG(Root, ROOT)
+
+SETPCGFLAG(Acct, ACCT)
+CLEARPCGFLAG(Acct, ACCT)
+TESTPCGFLAG(Acct, ACCT)
+
static inline int page_cgroup_nid(struct page_cgroup *pc)
{
return page_to_nid(pc->page);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9712ef7..18d2819 100644
--- a/mm/memcontrol.c
+++ b/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 = 0 */
@@ -196,6 +197,10 @@ enum charge_type {
#define PCGF_CACHE (1UL << PCG_CACHE)
#define PCGF_USED (1UL << PCG_USED)
#define PCGF_LOCK (1UL << PCG_LOCK)
+/* Not used, but added here for completeness */
+#define PCGF_ROOT (1UL << PCG_ROOT)
+#define PCGF_ACCT (1UL << PCG_ACCT)
+
static const unsigned long
pcg_default_flags[NR_CHARGE_TYPE] = {
PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* File Cache */
@@ -420,7 +425,7 @@ void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
return;
pc = lookup_page_cgroup(page);
/* can happen while we handle swapcache. */
- if (list_empty(&pc->lru) || !pc->mem_cgroup)
+ if ((!PageCgroupAcct(pc) && list_empty(&pc->lru)) || !pc->mem_cgroup)
return;
/*
* We don't check PCG_USED bit. It's cleared when the "page" is finally
@@ -429,6 +434,9 @@ void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
mz = page_cgroup_zoneinfo(pc);
mem = pc->mem_cgroup;
MEM_CGROUP_ZSTAT(mz, lru) -= 1;
+ ClearPageCgroupAcct(pc);
+ if (PageCgroupRoot(pc))
+ return;
list_del_init(&pc->lru);
return;
}
@@ -452,8 +460,8 @@ 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) || PageCgroupRoot(pc))
return;
mz = page_cgroup_zoneinfo(pc);
list_move(&pc->lru, &mz->lists[lru]);
@@ -477,6 +485,9 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
mz = page_cgroup_zoneinfo(pc);
MEM_CGROUP_ZSTAT(mz, lru) += 1;
+ SetPageCgroupAcct(pc);
+ if (PageCgroupRoot(pc))
+ return;
list_add(&pc->lru, &mz->lists[lru]);
}
@@ -1114,10 +1125,14 @@ 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];
+ if (mem == root_mem_cgroup)
+ SetPageCgroupRoot(pc);
+
mem_cgroup_charge_statistics(mem, pc, true);
unlock_page_cgroup(pc);
@@ -1521,6 +1536,8 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
mem_cgroup_charge_statistics(mem, pc, false);
ClearPageCgroupUsed(pc);
+ if (mem == root_mem_cgroup)
+ ClearPageCgroupRoot(pc);
/*
* pc->mem_cgroup is not cleared here. It will be accessed when it's
* freed from LRU. This is safe because uncharged page is expected not
@@ -2038,6 +2055,10 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
name = MEMFILE_ATTR(cft->private);
switch (name) {
case RES_LIMIT:
+ if (memcg == root_mem_cgroup) { /* 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)
@@ -2504,6 +2525,7 @@ 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;
@@ -2532,6 +2554,7 @@ 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);
}
diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 09b73c5..6145ff6 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -276,7 +276,6 @@ void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
#endif
-
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
static DEFINE_MUTEX(swap_cgroup_mutex);
--
Balbir
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