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/r/Ydza%2FzXKY9ATRoh6@xxxxxxxxxx/ [2] https://lore.kernel.org/r/20211130201652.2218636d@xxxxxxxxxxxxx/ Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx> Acked-by: Brian Geffon <bgeffon@xxxxxxxxxx> Acked-by: Jan Alexander Steffens (heftig) <heftig@xxxxxxxxxxxxx> Acked-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx> Acked-by: Steven Barrett <steven@xxxxxxxxxxxx> Acked-by: Suleiman Souhlal <suleiman@xxxxxxxxxx> Tested-by: Daniel Byrne <djbyrne@xxxxxxx> Tested-by: Donald Carr <d@xxxxxxxxxxxxxxx> Tested-by: Holger Hoffstätte <holger@xxxxxxxxxxxxxxxxxxxxxx> Tested-by: Konstantin Kharlamov <Hi-Angel@xxxxxxxxx> Tested-by: Shuang Zhai <szhai2@xxxxxxxxxxxxxxxx> Tested-by: Sofia Trinh <sofia.trinh@edi.works> Tested-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> --- include/linux/mmzone.h | 2 ++ mm/vmscan.c | 69 +++++++++++++++++++++++++++++++++++++++--- 2 files changed, 67 insertions(+), 4 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 525dbf5e14fa..16942bb9ccec 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -416,6 +416,8 @@ 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 */ diff --git a/mm/vmscan.c b/mm/vmscan.c index 33845796d100..4b7da68b8750 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4177,6 +4177,7 @@ 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); @@ -4302,7 +4303,8 @@ 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; @@ -4311,14 +4313,22 @@ 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; @@ -4327,11 +4337,18 @@ 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()); @@ -4357,12 +4374,29 @@ 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); + } } /* @@ -5077,6 +5111,28 @@ static void lru_gen_change_state(bool enable) * 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; @@ -5125,6 +5181,7 @@ 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 }; @@ -5140,12 +5197,16 @@ 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]); -- 2.35.1.1094.g7c7d902a7c-goog
