The patch titled
Subject: mm: multi-gen LRU: thrashing prevention
has been added to the -mm tree. Its filename is
mm-multi-gen-lru-thrashing-prevention.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-multi-gen-lru-thrashing-prevention.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-multi-gen-lru-thrashing-prevention.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Yu Zhao <yuzhao@xxxxxxxxxx>
Subject: mm: multi-gen LRU: thrashing prevention
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/
Link: https://lkml.kernel.org/r/20220407031525.2368067-12-yuzhao@xxxxxxxxxx
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>
Cc: Barry Song <baohua@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/mmzone.h~mm-multi-gen-lru-thrashing-prevention
+++ a/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 */
--- a/mm/vmscan.c~mm-multi-gen-lru-thrashing-prevention
+++ a/mm/vmscan.c
@@ -4192,6 +4192,7 @@ static void inc_max_seq(struct lruvec *l
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);
@@ -4317,7 +4318,8 @@ static long get_nr_evictable(struct lruv
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;
@@ -4326,14 +4328,22 @@ static void age_lruvec(struct lruvec *lr
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;
@@ -4342,11 +4352,18 @@ static void age_lruvec(struct lruvec *lr
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());
@@ -4372,12 +4389,29 @@ static void lru_gen_age_node(struct pgli
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);
+ }
}
/*
@@ -5092,6 +5126,28 @@ 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;
@@ -5140,6 +5196,7 @@ static struct kobj_attribute lru_gen_ena
);
static struct attribute *lru_gen_attrs[] = {
+ &lru_gen_min_ttl_attr.attr,
&lru_gen_enabled_attr.attr,
NULL
};
@@ -5155,12 +5212,16 @@ static struct attribute_group lru_gen_at
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]);
_
Patches currently in -mm which might be from yuzhao@xxxxxxxxxx are
mm-x86-arm64-add-arch_has_hw_pte_young.patch
mm-x86-add-config_arch_has_nonleaf_pmd_young.patch
mm-vmscanc-refactor-shrink_node.patch
revert-include-linux-mm_inlineh-fold-__update_lru_size-into-its-sole-caller.patch
mm-multi-gen-lru-groundwork.patch
mm-multi-gen-lru-minimal-implementation.patch
mm-multi-gen-lru-exploit-locality-in-rmap.patch
mm-multi-gen-lru-support-page-table-walks.patch
mm-multi-gen-lru-optimize-multiple-memcgs.patch
mm-multi-gen-lru-kill-switch.patch
mm-multi-gen-lru-thrashing-prevention.patch
mm-multi-gen-lru-debugfs-interface.patch
mm-multi-gen-lru-admin-guide.patch
mm-multi-gen-lru-design-doc.patch
