[patch 2/3] mm: hugetlb_cgroup: convert to lockless page counters

Johannes Weiner
2014-10-14T01:46:20Z

Abandon the spinlock-protected byte counters in favor of the unlocked
page counters in the hugetlb controller as well.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
---
Documentation/cgroups/hugetlb.txt | 2 +-
include/linux/hugetlb_cgroup.h | 1 -
init/Kconfig | 3 +-
mm/hugetlb_cgroup.c | 103 +++++++++++++++++++++-----------------
4 files changed, 61 insertions(+), 48 deletions(-)

diff --git a/Documentation/cgroups/hugetlb.txt b/Documentation/cgroups/hugetlb.txt
index a9faaca1f029..106245c3aecc 100644
--- a/Documentation/cgroups/hugetlb.txt
+++ b/Documentation/cgroups/hugetlb.txt
@@ -29,7 +29,7 @@ Brief summary of control files

hugetlb.<hugepagesize>.limit_in_bytes # set/show limit of "hugepagesize" hugetlb usage
hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb usage recorded
- hugetlb.<hugepagesize>.usage_in_bytes # show current res_counter usage for "hugepagesize" hugetlb
+ hugetlb.<hugepagesize>.usage_in_bytes # show current usage for "hugepagesize" hugetlb
hugetlb.<hugepagesize>.failcnt # show the number of allocation failure due to HugeTLB limit

For a system supporting two hugepage size (16M and 16G) the control
diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
index 0129f89cf98d..bcc853eccc85 100644
--- a/include/linux/hugetlb_cgroup.h
+++ b/include/linux/hugetlb_cgroup.h
@@ -16,7 +16,6 @@
#define _LINUX_HUGETLB_CGROUP_H

#include <linux/mmdebug.h>
-#include <linux/res_counter.h>

struct hugetlb_cgroup;
/*
diff --git a/init/Kconfig b/init/Kconfig
index 3fc577e9de75..d07a1c78d4e7 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1058,7 +1058,8 @@ config MEMCG_KMEM

config CGROUP_HUGETLB
bool "HugeTLB Resource Controller for Control Groups"
- depends on RESOURCE_COUNTERS && HUGETLB_PAGE
+ depends on HUGETLB_PAGE
+ select PAGE_COUNTER
default n
help
Provides a cgroup Resource Controller for HugeTLB pages.
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index a67c26e0f360..037e1c00a5b7 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -14,6 +14,7 @@
*/

#include <linux/cgroup.h>
+#include <linux/page_counter.h>
#include <linux/slab.h>
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
@@ -23,7 +24,7 @@ struct hugetlb_cgroup {
/*
* the counter to account for hugepages from hugetlb.
*/
- struct res_counter hugepage[HUGE_MAX_HSTATE];
+ struct page_counter hugepage[HUGE_MAX_HSTATE];
};

#define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
@@ -60,7 +61,7 @@ static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
int idx;

for (idx = 0; idx < hugetlb_max_hstate; idx++) {
- if ((res_counter_read_u64(&h_cg->hugepage[idx], RES_USAGE)) > 0)
+ if (page_counter_read(&h_cg->hugepage[idx]))
return true;
}
return false;
@@ -79,12 +80,12 @@ hugetlb_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)

if (parent_h_cgroup) {
for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
- res_counter_init(&h_cgroup->hugepage[idx],
- &parent_h_cgroup->hugepage[idx]);
+ page_counter_init(&h_cgroup->hugepage[idx],
+ &parent_h_cgroup->hugepage[idx]);
} else {
root_h_cgroup = h_cgroup;
for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
- res_counter_init(&h_cgroup->hugepage[idx], NULL);
+ page_counter_init(&h_cgroup->hugepage[idx], NULL);
}
return &h_cgroup->css;
}
@@ -108,9 +109,8 @@ static void hugetlb_cgroup_css_free(struct cgroup_subsys_state *css)
static void hugetlb_cgroup_move_parent(int idx, struct hugetlb_cgroup *h_cg,
struct page *page)
{
- int csize;
- struct res_counter *counter;
- struct res_counter *fail_res;
+ unsigned int nr_pages;
+ struct page_counter *counter;
struct hugetlb_cgroup *page_hcg;
struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(h_cg);

@@ -123,15 +123,15 @@ static void hugetlb_cgroup_move_parent(int idx, struct hugetlb_cgroup *h_cg,
if (!page_hcg || page_hcg != h_cg)
goto out;

- csize = PAGE_SIZE << compound_order(page);
+ nr_pages = 1 << compound_order(page);
if (!parent) {
parent = root_h_cgroup;
/* root has no limit */
- res_counter_charge_nofail(&parent->hugepage[idx],
- csize, &fail_res);
+ page_counter_charge(&parent->hugepage[idx], nr_pages);
}
counter = &h_cg->hugepage[idx];
- res_counter_uncharge_until(counter, counter->parent, csize);
+ /* Take the pages off the local counter */
+ page_counter_cancel(counter, nr_pages);

set_hugetlb_cgroup(page, parent);
out:
@@ -166,9 +166,8 @@ int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
struct hugetlb_cgroup **ptr)
{
int ret = 0;
- struct res_counter *fail_res;
+ struct page_counter *counter;
struct hugetlb_cgroup *h_cg = NULL;
- unsigned long csize = nr_pages * PAGE_SIZE;

if (hugetlb_cgroup_disabled())
goto done;
@@ -187,7 +186,7 @@ again:
}
rcu_read_unlock();

- ret = res_counter_charge(&h_cg->hugepage[idx], csize, &fail_res);
+ ret = page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter);
css_put(&h_cg->css);
done:
*ptr = h_cg;
@@ -213,7 +212,6 @@ void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
struct page *page)
{
struct hugetlb_cgroup *h_cg;
- unsigned long csize = nr_pages * PAGE_SIZE;

if (hugetlb_cgroup_disabled())
return;
@@ -222,61 +220,76 @@ void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
if (unlikely(!h_cg))
return;
set_hugetlb_cgroup(page, NULL);
- res_counter_uncharge(&h_cg->hugepage[idx], csize);
+ page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
return;
}

void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
struct hugetlb_cgroup *h_cg)
{
- unsigned long csize = nr_pages * PAGE_SIZE;
-
if (hugetlb_cgroup_disabled() || !h_cg)
return;

if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
return;

- res_counter_uncharge(&h_cg->hugepage[idx], csize);
+ page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
return;
}

+enum {
+ RES_USAGE,
+ RES_LIMIT,
+ RES_MAX_USAGE,
+ RES_FAILCNT,
+};
+
static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css,
struct cftype *cft)
{
- int idx, name;
+ struct page_counter *counter;
struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);

- idx = MEMFILE_IDX(cft->private);
- name = MEMFILE_ATTR(cft->private);
+ counter = &h_cg->hugepage[MEMFILE_IDX(cft->private)];

- return res_counter_read_u64(&h_cg->hugepage[idx], name);
+ switch (MEMFILE_ATTR(cft->private)) {
+ case RES_USAGE:
+ return (u64)page_counter_read(counter) * PAGE_SIZE;
+ case RES_LIMIT:
+ return (u64)counter->limit * PAGE_SIZE;
+ case RES_MAX_USAGE:
+ return (u64)counter->watermark * PAGE_SIZE;
+ case RES_FAILCNT:
+ return counter->failcnt;
+ default:
+ BUG();
+ }
}

+static DEFINE_MUTEX(hugetlb_limit_mutex);
+
static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
- int idx, name, ret;
- unsigned long long val;
+ int ret, idx;
+ unsigned long nr_pages;
struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

+ if (hugetlb_cgroup_is_root(h_cg)) /* Can't set limit on root */
+ return -EINVAL;
+
buf = strstrip(buf);
+ ret = page_counter_memparse(buf, &nr_pages);
+ if (ret)
+ return ret;
+
idx = MEMFILE_IDX(of_cft(of)->private);
- name = MEMFILE_ATTR(of_cft(of)->private);

- switch (name) {
+ switch (MEMFILE_ATTR(of_cft(of)->private)) {
case RES_LIMIT:
- if (hugetlb_cgroup_is_root(h_cg)) {
- /* Can't set limit on root */
- ret = -EINVAL;
- break;
- }
- /* This function does all necessary parse...reuse it */
- ret = res_counter_memparse_write_strategy(buf, &val);
- if (ret)
- break;
- val = ALIGN(val, 1ULL << huge_page_shift(&hstates[idx]));
- ret = res_counter_set_limit(&h_cg->hugepage[idx], val);
+ mutex_lock(&hugetlb_limit_mutex);
+ ret = page_counter_limit(&h_cg->hugepage[idx], nr_pages);
+ mutex_unlock(&hugetlb_limit_mutex);
break;
default:
ret = -EINVAL;
@@ -288,18 +301,18 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
- int idx, name, ret = 0;
+ int ret = 0;
+ struct page_counter *counter;
struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

- idx = MEMFILE_IDX(of_cft(of)->private);
- name = MEMFILE_ATTR(of_cft(of)->private);
+ counter = &h_cg->hugepage[MEMFILE_IDX(of_cft(of)->private)];

- switch (name) {
+ switch (MEMFILE_ATTR(of_cft(of)->private)) {
case RES_MAX_USAGE:
- res_counter_reset_max(&h_cg->hugepage[idx]);
+ page_counter_reset_watermark(counter);
break;
case RES_FAILCNT:
- res_counter_reset_failcnt(&h_cg->hugepage[idx]);
+ counter->failcnt = 0;
break;
default:
ret = -EINVAL;
--
2.1.2