[patch 087/163] mm, memcg: unify reclaim retry limits with page allocator

Andrew Morton
2020-08-07T06:22:01Z

From: Chris Down <chris@chrisdown.name>
Subject: mm, memcg: unify reclaim retry limits with page allocator

Reclaim retries have been set to 5 since the beginning of time in
commit 66e1707bc346 ("Memory controller: add per cgroup LRU and
reclaim"). However, we now have a generally agreed-upon standard for
page reclaim: MAX_RECLAIM_RETRIES (currently 16), added many years later
in commit 0a0337e0d1d1 ("mm, oom: rework oom detection").

In the absence of a compelling reason to declare an OOM earlier in memcg
context than page allocator context, it seems reasonable to supplant
MEM_CGROUP_RECLAIM_RETRIES with MAX_RECLAIM_RETRIES, making the page
allocator and memcg internals more similar in semantics when reclaim
fails to produce results, avoiding premature OOMs or throttling.

Link: http://lkml.kernel.org/r/da557856c9c7654308eaff4eedc1952a95e8df5f.1594640214.git.chris@chrisdown.name
Signed-off-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/memcontrol.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)

--- a/mm/memcontrol.c~mm-memcg-unify-reclaim-retry-limits-with-page-allocator
+++ a/mm/memcontrol.c
@@ -73,9 +73,6 @@ EXPORT_SYMBOL(memory_cgrp_subsys);

struct mem_cgroup *root_mem_cgroup __read_mostly;

-/* The number of times we should retry reclaim failures before giving up. */
-#define MEM_CGROUP_RECLAIM_RETRIES 5
-
/* Socket memory accounting disabled? */
static bool cgroup_memory_nosocket;

@@ -2538,7 +2535,7 @@ void mem_cgroup_handle_over_high(void)
unsigned long pflags;
unsigned long nr_reclaimed;
unsigned int nr_pages = current->memcg_nr_pages_over_high;
- int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
+ int nr_retries = MAX_RECLAIM_RETRIES;
struct mem_cgroup *memcg;
bool in_retry = false;

@@ -2615,7 +2612,7 @@ static int try_charge(struct mem_cgroup
unsigned int nr_pages)
{
unsigned int batch = max(MEMCG_CHARGE_BATCH, nr_pages);
- int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
+ int nr_retries = MAX_RECLAIM_RETRIES;
struct mem_cgroup *mem_over_limit;
struct page_counter *counter;
unsigned long nr_reclaimed;
@@ -2734,7 +2731,7 @@ retry:
get_order(nr_pages * PAGE_SIZE));
switch (oom_status) {
case OOM_SUCCESS:
- nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
+ nr_retries = MAX_RECLAIM_RETRIES;
goto retry;
case OOM_FAILED:
goto force;
@@ -3414,7 +3411,7 @@ static inline bool memcg_has_children(st
*/
static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
{
- int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
+ int nr_retries = MAX_RECLAIM_RETRIES;

/* we call try-to-free pages for make this cgroup empty */
lru_add_drain_all();
@@ -6235,7 +6232,7 @@ static ssize_t memory_high_write(struct
char *buf, size_t nbytes, loff_t off)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
- unsigned int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
+ unsigned int nr_retries = MAX_RECLAIM_RETRIES;
bool drained = false;
unsigned long high;
int err;
@@ -6283,7 +6280,7 @@ static ssize_t memory_max_write(struct k
char *buf, size_t nbytes, loff_t off)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
- unsigned int nr_reclaims = MEM_CGROUP_RECLAIM_RETRIES;
+ unsigned int nr_reclaims = MAX_RECLAIM_RETRIES;
bool drained = false;
unsigned long max;
int err;
_