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FROMLIST: mm: multi-gen LRU: thrashing prevention

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Add /sys/kernel/mm/lru_gen/min_ttl_ms for thrashing prevention, as
requested by many desktop users [1].

When set to value N, it prevents the working set of N milliseconds
from getting evicted. The OOM killer is triggered if this working set
cannot be kept in memory. Based on the average human detectable lag
(~100ms), N=1000 usually eliminates intolerable lags due to thrashing.
Larger values like N=3000 make lags less noticeable at the risk of
premature OOM kills.

Compared with the size-based approach, e.g., [2], this time-based
approach has the following advantages:
1. It is easier to configure because it is agnostic to applications
   and memory sizes.
2. It is more reliable because it is directly wired to the OOM killer.

[1] https://lore.kernel.org/lkml/Ydza%2FzXKY9ATRoh6@google.com/
[2] https://lore.kernel.org/lkml/20211130201652.2218636d@mail.inbox.lv/

Link: https://lore.kernel.org/r/20220309021230.721028-12-yuzhao@google.com/
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Brian Geffon <bgeffon@google.com>
Acked-by: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Acked-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Acked-by: Steven Barrett <steven@liquorix.net>
Acked-by: Suleiman Souhlal <suleiman@google.com>
Tested-by: Daniel Byrne <djbyrne@mtu.edu>
Tested-by: Donald Carr <d@chaos-reins.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
Tested-by: Shuang Zhai <szhai2@cs.rochester.edu>
Tested-by: Sofia Trinh <sofia.trinh@edi.works>
Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Bug: 227651406
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Change-Id: I482d33f3beaf7723d2f3eeaaa5b4f12bcb9b48a1
This commit is contained in:
Yu Zhao
2022-01-27 20:08:50 -07:00
committed by Todd Kjos
parent 76fdc1010b
commit 96f4a592d3
2 changed files with 67 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/mmzone.h
View File

@@ -376,6 +376,8 @@ struct lru_gen_struct {
unsigned long max_seq;
/* the eviction increments the oldest generation numbers */
unsigned long min_seq[ANON_AND_FILE];
/* the birth time of each generation in jiffies */
unsigned long timestamps[MAX_NR_GENS];
/* the multi-gen LRU lists */
struct list_head lists[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES];
/* the sizes of the above lists */

69
mm/vmscan.c
View File

@@ -3801,6 +3801,7 @@ static void inc_max_seq(struct lruvec *lruvec)
for (type = 0; type < ANON_AND_FILE; type++)
reset_ctrl_pos(lruvec, type, false);
WRITE_ONCE(lrugen->timestamps[next], jiffies);
/* make sure preceding modifications appear */
smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1);
@@ -3926,7 +3927,8 @@ static long get_nr_evictable(struct lruvec *lruvec, unsigned long max_seq,
return total > 0 ? total : 0;
}
static void age_lruvec(struct lruvec *lruvec, struct scan_control *sc)
static bool age_lruvec(struct lruvec *lruvec, struct scan_control *sc,
unsigned long min_ttl)
{
bool need_aging;
long nr_to_scan;
@@ -3935,14 +3937,22 @@ static void age_lruvec(struct lruvec *lruvec, struct scan_control *sc)
DEFINE_MAX_SEQ(lruvec);
DEFINE_MIN_SEQ(lruvec);
if (min_ttl) {
int gen = lru_gen_from_seq(min_seq[LRU_GEN_FILE]);
unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
if (time_is_after_jiffies(birth + min_ttl))
return false;
}
mem_cgroup_calculate_protection(NULL, memcg);
if (mem_cgroup_below_min(memcg))
return;
return false;
nr_to_scan = get_nr_evictable(lruvec, max_seq, min_seq, swappiness, &need_aging);
if (!nr_to_scan)
return;
return false;
nr_to_scan >>= sc->priority;
@@ -3951,11 +3961,18 @@ static void age_lruvec(struct lruvec *lruvec, struct scan_control *sc)
if (nr_to_scan && need_aging && (!mem_cgroup_below_low(memcg) || sc->memcg_low_reclaim))
try_to_inc_max_seq(lruvec, max_seq, sc, swappiness, false);
return true;
}
/* to protect the working set of the last N jiffies */
static unsigned long lru_gen_min_ttl __read_mostly;
static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
{
struct mem_cgroup *memcg;
bool success = false;
unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);
VM_BUG_ON(!current_is_kswapd());
@@ -3981,12 +3998,29 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
do {
struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
age_lruvec(lruvec, sc);
if (age_lruvec(lruvec, sc, min_ttl))
success = true;
cond_resched();
} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
current->reclaim_state->mm_walk = NULL;
/*
* The main goal is to OOM kill if every generation from all memcgs is
* younger than min_ttl. However, another theoretical possibility is all
* memcgs are either below min or empty.
*/
if (!success && mutex_trylock(&oom_lock)) {
struct oom_control oc = {
.gfp_mask = sc->gfp_mask,
.order = sc->order,
};
out_of_memory(&oc);
mutex_unlock(&oom_lock);
}
}
/*
@@ -4708,6 +4742,28 @@ unlock:
* sysfs interface
******************************************************************************/
static ssize_t show_min_ttl(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl)));
}
static ssize_t store_min_ttl(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t len)
{
unsigned int msecs;
if (kstrtouint(buf, 0, &msecs))
return -EINVAL;
WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs));
return len;
}
static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR(
min_ttl_ms, 0644, show_min_ttl, store_min_ttl
);
static ssize_t show_enable(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{
unsigned int caps = 0;
@@ -4756,6 +4812,7 @@ static struct kobj_attribute lru_gen_enabled_attr = __ATTR(
);
static struct attribute *lru_gen_attrs[] = {
&lru_gen_min_ttl_attr.attr,
&lru_gen_enabled_attr.attr,
NULL
};
@@ -4771,12 +4828,16 @@ static struct attribute_group lru_gen_attr_group = {
void lru_gen_init_lruvec(struct lruvec *lruvec)
{
int i;
int gen, type, zone;
struct lru_gen_struct *lrugen = &lruvec->lrugen;
lrugen->max_seq = MIN_NR_GENS + 1;
lrugen->enabled = lru_gen_enabled();
for (i = 0; i <= MIN_NR_GENS + 1; i++)
lrugen->timestamps[i] = jiffies;
for_each_gen_type_zone(gen, type, zone)
INIT_LIST_HEAD(&lrugen->lists[gen][type][zone]);