Memory protection (min/low) requires a constant tracking of
protected memory usage. propagate_protected_usage() is called
on each page counters update and does a number of operations
even in cases when the actual memory protection functionality
is not supported (e.g. hugetlb cgroups or memcg swap counters).
It's obviously inefficient and leads to a waste of CPU cycles.
It can be addressed by calling propagate_protected_usage() only
for the counters which do support memory guarantees. As of now
it's only memcg->memory - the unified memory memcg counter.
Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
---
include/linux/page_counter.h | 8 +++++++-
mm/hugetlb_cgroup.c | 4 ++--
mm/memcontrol.c | 16 ++++++++--------
mm/page_counter.c | 16 +++++++++++++---
4 files changed, 30 insertions(+), 14 deletions(-)
diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h
index 860f313182e7..b31fd5b208aa 100644
--- a/include/linux/page_counter.h
+++ b/include/linux/page_counter.h
@@ -32,6 +32,7 @@ struct page_counter {
/* Keep all the read most fields in a separete cacheline. */
CACHELINE_PADDING(_pad2_);
+ bool protection_support;
unsigned long min;
unsigned long low;
unsigned long high;
@@ -45,12 +46,17 @@ struct page_counter {
#define PAGE_COUNTER_MAX (LONG_MAX / PAGE_SIZE)
#endif
+/*
+ * Protection is supported only for the first counter (with id 0).
+ */
static inline void page_counter_init(struct page_counter *counter,
- struct page_counter *parent)
+ struct page_counter *parent,
+ bool protection_support)
{
atomic_long_set(&counter->usage, 0);
counter->max = PAGE_COUNTER_MAX;
counter->parent = parent;
+ counter->protection_support = protection_support;
}
static inline unsigned long page_counter_read(struct page_counter *counter)
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index f443a56409a9..d8d0e665caed 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -114,10 +114,10 @@ static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
}
page_counter_init(hugetlb_cgroup_counter_from_cgroup(h_cgroup,
idx),
- fault_parent);
+ fault_parent, false);
page_counter_init(
hugetlb_cgroup_counter_from_cgroup_rsvd(h_cgroup, idx),
- rsvd_parent);
+ rsvd_parent, false);
limit = round_down(PAGE_COUNTER_MAX,
pages_per_huge_page(&hstates[idx]));
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 87fa448b731f..45c0f816a974 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3579,21 +3579,21 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
if (parent) {
WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
- page_counter_init(&memcg->memory, &parent->memory);
- page_counter_init(&memcg->swap, &parent->swap);
+ page_counter_init(&memcg->memory, &parent->memory, true);
+ page_counter_init(&memcg->swap, &parent->swap, false);
#ifdef CONFIG_MEMCG_V1
WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));
- page_counter_init(&memcg->kmem, &parent->kmem);
- page_counter_init(&memcg->tcpmem, &parent->tcpmem);
+ page_counter_init(&memcg->kmem, &parent->kmem, false);
+ page_counter_init(&memcg->tcpmem, &parent->tcpmem, false);
#endif
} else {
init_memcg_stats();
init_memcg_events();
- page_counter_init(&memcg->memory, NULL);
- page_counter_init(&memcg->swap, NULL);
+ page_counter_init(&memcg->memory, NULL, true);
+ page_counter_init(&memcg->swap, NULL, false);
#ifdef CONFIG_MEMCG_V1
- page_counter_init(&memcg->kmem, NULL);
- page_counter_init(&memcg->tcpmem, NULL);
+ page_counter_init(&memcg->kmem, NULL, false);
+ page_counter_init(&memcg->tcpmem, NULL, false);
#endif
root_mem_cgroup = memcg;
return &memcg->css;
diff --git a/mm/page_counter.c b/mm/page_counter.c
index ad9bdde5d5d2..a54382a58ace 100644
--- a/mm/page_counter.c
+++ b/mm/page_counter.c
@@ -13,6 +13,11 @@
#include <linux/bug.h>
#include <asm/page.h>
+static bool track_protection(struct page_counter *c)
+{
+ return c->protection_support;
+}
+
static void propagate_protected_usage(struct page_counter *c,
unsigned long usage)
{
@@ -57,7 +62,8 @@ void page_counter_cancel(struct page_counter *counter, unsigned long nr_pages)
new = 0;
atomic_long_set(&counter->usage, new);
}
- propagate_protected_usage(counter, new);
+ if (track_protection(counter))
+ propagate_protected_usage(counter, new);
}
/**
@@ -70,12 +76,14 @@ void page_counter_cancel(struct page_counter *counter, unsigned long nr_pages)
void page_counter_charge(struct page_counter *counter, unsigned long nr_pages)
{
struct page_counter *c;
+ bool protection = track_protection(counter);
for (c = counter; c; c = c->parent) {
long new;
new = atomic_long_add_return(nr_pages, &c->usage);
- propagate_protected_usage(c, new);
+ if (protection)
+ propagate_protected_usage(c, new);
/*
* This is indeed racy, but we can live with some
* inaccuracy in the watermark.
@@ -112,6 +120,7 @@ bool page_counter_try_charge(struct page_counter *counter,
struct page_counter **fail)
{
struct page_counter *c;
+ bool protection = track_protection(counter);
for (c = counter; c; c = c->parent) {
long new;
@@ -141,7 +150,8 @@ bool page_counter_try_charge(struct page_counter *counter,
*fail = c;
goto failed;
}
- propagate_protected_usage(c, new);
+ if (protection)
+ propagate_protected_usage(c, new);
/* see comment on page_counter_charge */
if (new > READ_ONCE(c->local_watermark)) {
--
2.46.0.rc1.232.g9752f9e123-goog
