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mm: memcg: don't call propagate_protected_usage() needlessly

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Patch series "mm: memcg: page counters optimizations", v3.

This patchset contains 3 independent small optimizations of page counters.


This patch (of 3):

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.

Link: https://lkml.kernel.org/r/20240726203110.1577216-2-roman.gushchin@linux.dev
Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Roman Gushchin 2024-07-26 20:31:08 +00:00 committed by Andrew Morton
parent 6c469957cd
commit f77bd4b14c
4 changed files with 31 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/page_counter.h
View File

@ -31,6 +31,7 @@ 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;
@ -44,12 +45,17 @@ 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)

4
mm/hugetlb_cgroup.c
View File

@ -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]));

16
mm/memcontrol.c
View File

@ -3596,21 +3596,21 @@ 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;

17
mm/page_counter.c
View File

@ -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.
@ -99,6 +107,7 @@ 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;
@ -128,7 +137,9 @@ 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);
/*
* Just like with failcnt, we can live with some
* inaccuracy in the watermark.