On Wed, Mar 9, 2022 at 3:48 PM Yu Zhao <yuzhao@xxxxxxxxxx> wrote: > > 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. > how are userspace oom daemons like android lmkd, systemd-oomd supposed to work with this time-based oom killer? only one of min_ttl_ms and userspace daemon should be enabled? or both should be enabled at the same time? > [1] https://lore.kernel.org/lkml/Ydza%2FzXKY9ATRoh6@xxxxxxxxxx/ > [2] https://lore.kernel.org/lkml/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 116c9237e401..f98f9ce50e67 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -403,6 +403,8 @@ 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 55cc7d6b018b..6aa083b8bb26 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4229,6 +4229,7 @@ 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); > > @@ -4340,7 +4341,8 @@ 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; > @@ -4349,14 +4351,22 @@ 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; > > @@ -4365,11 +4375,18 @@ 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()); > > @@ -4395,12 +4412,29 @@ 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); > + } > } > > /* > @@ -5112,6 +5146,28 @@ 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; > @@ -5160,6 +5216,7 @@ 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 > }; > @@ -5175,12 +5232,16 @@ 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]); > > -- > 2.35.1.616.g0bdcbb4464-goog > Thanks Barry
