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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
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8
include/linux/page_counter.h
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@@ -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)