Add /sys/kernel/mm/lru_gen/enabled as a runtime kill switch. Add /sys/kernel/mm/lru_gen/min_ttl_ms for thrashing prevention. Compared with the size-based approach, e.g., [1], this time-based approach has the following advantages: 1) It's easier to configure because it's agnostic to applications and memory sizes. 2) It's more reliable because it's directly wired to the OOM killer. Add /sys/kernel/debug/lru_gen for working set estimation and proactive reclaim. Compared with the page table-based approach and the PFN-based approach, e.g., mm/damon/[vp]addr.c, this lruvec-based approach has the following advantages: 1) It offers better choices because it's aware of memcgs, NUMA nodes, shared mappings and unmapped page cache. 2) It's more scalable because it's O(nr_hot_evictable_pages), whereas the PFN-based approach is O(nr_total_pages). Add /sys/kernel/debug/lru_gen_full for debugging. [1] https://lore.kernel.org/lkml/20211130201652.2218636d@xxxxxxxxxxxxx/ Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx> Tested-by: Konstantin Kharlamov <Hi-Angel@xxxxxxxxx> --- Documentation/vm/index.rst | 1 + Documentation/vm/multigen_lru.rst | 62 +++++ include/linux/nodemask.h | 1 + mm/vmscan.c | 415 ++++++++++++++++++++++++++++++ 4 files changed, 479 insertions(+) create mode 100644 Documentation/vm/multigen_lru.rst diff --git a/Documentation/vm/index.rst b/Documentation/vm/index.rst index 6f5ffef4b716..f25e755b4ff4 100644 --- a/Documentation/vm/index.rst +++ b/Documentation/vm/index.rst @@ -38,3 +38,4 @@ algorithms. If you are looking for advice on simply allocating memory, see the unevictable-lru z3fold zsmalloc + multigen_lru diff --git a/Documentation/vm/multigen_lru.rst b/Documentation/vm/multigen_lru.rst new file mode 100644 index 000000000000..6f9e0181348b --- /dev/null +++ b/Documentation/vm/multigen_lru.rst @@ -0,0 +1,62 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================== +Multigenerational LRU +===================== + +Quick start +=========== +Runtime configurations +---------------------- +:Required: Write ``1`` to ``/sys/kernel/mm/lru_gen/enable`` if the + feature wasn't enabled by default. + +Recipes +======= +Personal computers +------------------ +:Thrashing prevention: Write ``N`` to + ``/sys/kernel/mm/lru_gen/min_ttl_ms`` to prevent the working set of + ``N`` milliseconds from getting evicted. The OOM killer is invoked if + this working set can't 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 cost of more OOM kills. + +Data centers +------------ +:Debugfs interface: ``/sys/kernel/debug/lru_gen`` has the following + format: + :: + + memcg memcg_id memcg_path + node node_id + min_gen birth_time anon_size file_size + ... + max_gen birth_time anon_size file_size + + ``min_gen`` is the oldest generation number and ``max_gen`` is the + youngest generation number. ``birth_time`` is in milliseconds. + ``anon_size`` and ``file_size`` are in pages. + + This file also accepts commands in the following subsections. + Multiple command lines are supported, so does concatenation with + delimiters ``,`` and ``;``. + + ``/sys/kernel/debug/lru_gen_full`` contains additional stats for + debugging. + +:Working set estimation: Write ``+ memcg_id node_id max_gen + [can_swap [full_scan]]`` to ``/sys/kernel/debug/lru_gen`` to trigger + the aging. It scans PTEs for accessed pages and promotes them to the + youngest generation ``max_gen``. Then it creates a new generation + ``max_gen+1``. Set ``can_swap`` to 1 to scan for accessed anon pages + when swap is off. Set ``full_scan`` to 0 to reduce the overhead as + well as the coverage when scanning PTEs. + +:Proactive reclaim: Write ``- memcg_id node_id min_gen [swappiness + [nr_to_reclaim]]`` to ``/sys/kernel/debug/lru_gen`` to trigger the + eviction. It evicts generations less than or equal to ``min_gen``. + ``min_gen`` should be less than ``max_gen-1`` as ``max_gen`` and + ``max_gen-1`` aren't fully aged and therefore can't be evicted. Use + ``nr_to_reclaim`` to limit the number of pages to evict. diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h index 567c3ddba2c4..90840c459abc 100644 --- a/include/linux/nodemask.h +++ b/include/linux/nodemask.h @@ -486,6 +486,7 @@ static inline int num_node_state(enum node_states state) #define first_online_node 0 #define first_memory_node 0 #define next_online_node(nid) (MAX_NUMNODES) +#define next_memory_node(nid) (MAX_NUMNODES) #define nr_node_ids 1U #define nr_online_nodes 1U diff --git a/mm/vmscan.c b/mm/vmscan.c index b232f711dbdb..20f45ff849fc 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -53,6 +53,8 @@ #include <linux/memory.h> #include <linux/pagewalk.h> #include <linux/shmem_fs.h> +#include <linux/ctype.h> +#include <linux/debugfs.h> #include <asm/tlbflush.h> #include <asm/div64.h> @@ -5021,6 +5023,413 @@ static void lru_gen_change_state(bool enable) mem_hotplug_done(); } +/****************************************************************************** + * 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, 10, &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) +{ + return snprintf(buf, PAGE_SIZE, "%d\n", lru_gen_enabled()); +} + +static ssize_t store_enable(struct kobject *kobj, struct kobj_attribute *attr, + const char *buf, size_t len) +{ + bool enable; + + if (kstrtobool(buf, &enable)) + return -EINVAL; + + lru_gen_change_state(enable); + + return len; +} + +static struct kobj_attribute lru_gen_enabled_attr = __ATTR( + enabled, 0644, show_enable, store_enable +); + +static struct attribute *lru_gen_attrs[] = { + &lru_gen_min_ttl_attr.attr, + &lru_gen_enabled_attr.attr, + NULL +}; + +static struct attribute_group lru_gen_attr_group = { + .name = "lru_gen", + .attrs = lru_gen_attrs, +}; + +/****************************************************************************** + * debugfs interface + ******************************************************************************/ + +static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos) +{ + struct mem_cgroup *memcg; + loff_t nr_to_skip = *pos; + + m->private = kvmalloc(PATH_MAX, GFP_KERNEL); + if (!m->private) + return ERR_PTR(-ENOMEM); + + memcg = mem_cgroup_iter(NULL, NULL, NULL); + do { + int nid; + + for_each_node_state(nid, N_MEMORY) { + if (!nr_to_skip--) + return get_lruvec(memcg, nid); + } + } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); + + return NULL; +} + +static void lru_gen_seq_stop(struct seq_file *m, void *v) +{ + if (!IS_ERR_OR_NULL(v)) + mem_cgroup_iter_break(NULL, lruvec_memcg(v)); + + kvfree(m->private); + m->private = NULL; +} + +static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos) +{ + int nid = lruvec_pgdat(v)->node_id; + struct mem_cgroup *memcg = lruvec_memcg(v); + + ++*pos; + + nid = next_memory_node(nid); + if (nid == MAX_NUMNODES) { + memcg = mem_cgroup_iter(NULL, memcg, NULL); + if (!memcg) + return NULL; + + nid = first_memory_node; + } + + return get_lruvec(memcg, nid); +} + +static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, + unsigned long max_seq, unsigned long *min_seq, + unsigned long seq) +{ + int i; + int type, tier; + int hist = lru_hist_from_seq(seq); + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + for (tier = 0; tier < MAX_NR_TIERS; tier++) { + seq_printf(m, " %10d", tier); + for (type = 0; type < ANON_AND_FILE; type++) { + unsigned long n[3] = {}; + + if (seq == max_seq) { + n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]); + n[1] = READ_ONCE(lrugen->avg_total[type][tier]); + + seq_printf(m, " %10luR %10luT %10lu ", n[0], n[1], n[2]); + } else if (seq == min_seq[type] || NR_HIST_GENS > 1) { + n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]); + n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]); + if (tier) + n[2] = READ_ONCE(lrugen->promoted[hist][type][tier - 1]); + + seq_printf(m, " %10lur %10lue %10lup", n[0], n[1], n[2]); + } else + seq_puts(m, " 0 0 0 "); + } + seq_putc(m, '\n'); + } + + seq_puts(m, " "); + for (i = 0; i < NR_MM_STATS; i++) { + if (seq == max_seq && NR_HIST_GENS == 1) + seq_printf(m, " %10lu%c", READ_ONCE(lruvec->mm_state.stats[hist][i]), + toupper(MM_STAT_CODES[i])); + else if (seq != max_seq && NR_HIST_GENS > 1) + seq_printf(m, " %10lu%c", READ_ONCE(lruvec->mm_state.stats[hist][i]), + MM_STAT_CODES[i]); + else + seq_puts(m, " 0 "); + } + seq_putc(m, '\n'); +} + +static int lru_gen_seq_show(struct seq_file *m, void *v) +{ + unsigned long seq; + bool full = !debugfs_real_fops(m->file)->write; + struct lruvec *lruvec = v; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + int nid = lruvec_pgdat(lruvec)->node_id; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + DEFINE_MAX_SEQ(lruvec); + DEFINE_MIN_SEQ(lruvec); + + if (nid == first_memory_node) { + const char *path = memcg ? m->private : ""; + +#ifdef CONFIG_MEMCG + if (memcg) + cgroup_path(memcg->css.cgroup, m->private, PATH_MAX); +#endif + seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path); + } + + seq_printf(m, " node %5d\n", nid); + + if (!full) + seq = min_seq[0]; + else if (max_seq >= MAX_NR_GENS) + seq = max_seq - MAX_NR_GENS + 1; + else + seq = 0; + + for (; seq <= max_seq; seq++) { + int gen, type, zone; + unsigned int msecs; + + gen = lru_gen_from_seq(seq); + msecs = jiffies_to_msecs(jiffies - READ_ONCE(lrugen->timestamps[gen])); + + seq_printf(m, " %10lu %10u", seq, msecs); + + for (type = 0; type < ANON_AND_FILE; type++) { + long size = 0; + + if (seq < min_seq[type]) { + seq_puts(m, " -0 "); + continue; + } + + for (zone = 0; zone < MAX_NR_ZONES; zone++) + size += READ_ONCE(lrugen->nr_pages[gen][type][zone]); + + seq_printf(m, " %10lu ", max(size, 0L)); + } + + seq_putc(m, '\n'); + + if (full) + lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq); + } + + return 0; +} + +static const struct seq_operations lru_gen_seq_ops = { + .start = lru_gen_seq_start, + .stop = lru_gen_seq_stop, + .next = lru_gen_seq_next, + .show = lru_gen_seq_show, +}; + +static int run_aging(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc, + bool can_swap, bool full_scan) +{ + DEFINE_MAX_SEQ(lruvec); + + if (seq == max_seq) + try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, full_scan); + + return seq > max_seq ? -EINVAL : 0; +} + +static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc, + int swappiness, unsigned long nr_to_reclaim) +{ + struct blk_plug plug; + int err = -EINTR; + DEFINE_MAX_SEQ(lruvec); + + if (max_seq < seq + MIN_NR_GENS) + return -EINVAL; + + sc->nr_reclaimed = 0; + + blk_start_plug(&plug); + + while (!signal_pending(current)) { + DEFINE_MIN_SEQ(lruvec); + + if (seq < min_seq[!swappiness] || sc->nr_reclaimed >= nr_to_reclaim || + !evict_folios(lruvec, sc, swappiness, NULL)) { + err = 0; + break; + } + + cond_resched(); + } + + blk_finish_plug(&plug); + + return err; +} + +static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq, + struct scan_control *sc, int swappiness, unsigned long opt) +{ + struct lruvec *lruvec; + int err = -EINVAL; + struct mem_cgroup *memcg = NULL; + + if (!mem_cgroup_disabled()) { + rcu_read_lock(); + memcg = mem_cgroup_from_id(memcg_id); +#ifdef CONFIG_MEMCG + if (memcg && !css_tryget(&memcg->css)) + memcg = NULL; +#endif + rcu_read_unlock(); + + if (!memcg) + goto done; + } + if (memcg_id != mem_cgroup_id(memcg)) + goto done; + + if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY)) + goto done; + + lruvec = get_lruvec(memcg, nid); + + if (swappiness < 0) + swappiness = get_swappiness(memcg); + else if (swappiness > 200) + goto done; + + switch (cmd) { + case '+': + err = run_aging(lruvec, seq, sc, swappiness, opt); + break; + case '-': + err = run_eviction(lruvec, seq, sc, swappiness, opt); + break; + } +done: + mem_cgroup_put(memcg); + + return err; +} + +static ssize_t lru_gen_seq_write(struct file *file, const char __user *src, + size_t len, loff_t *pos) +{ + void *buf; + char *cur, *next; + unsigned int flags; + int err = 0; + struct scan_control sc = { + .may_writepage = 1, + .may_unmap = 1, + .may_swap = 1, + .reclaim_idx = MAX_NR_ZONES - 1, + .gfp_mask = GFP_KERNEL, + }; + + buf = kvmalloc(len + 1, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + if (copy_from_user(buf, src, len)) { + kvfree(buf); + return -EFAULT; + } + + next = buf; + next[len] = '\0'; + + sc.reclaim_state.mm_walk = alloc_mm_walk(); + if (!sc.reclaim_state.mm_walk) { + kvfree(buf); + return -ENOMEM; + } + + flags = memalloc_noreclaim_save(); + set_task_reclaim_state(current, &sc.reclaim_state); + + while ((cur = strsep(&next, ",;\n"))) { + int n; + int end; + char cmd; + unsigned int memcg_id; + unsigned int nid; + unsigned long seq; + unsigned int swappiness = -1; + unsigned long opt = -1; + + cur = skip_spaces(cur); + if (!*cur) + continue; + + n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid, + &seq, &end, &swappiness, &end, &opt, &end); + if (n < 4 || cur[end]) { + err = -EINVAL; + break; + } + + err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt); + if (err) + break; + } + + set_task_reclaim_state(current, NULL); + memalloc_noreclaim_restore(flags); + + free_mm_walk(sc.reclaim_state.mm_walk); + kvfree(buf); + + return err ? : len; +} + +static int lru_gen_seq_open(struct inode *inode, struct file *file) +{ + return seq_open(file, &lru_gen_seq_ops); +} + +static const struct file_operations lru_gen_rw_fops = { + .open = lru_gen_seq_open, + .read = seq_read, + .write = lru_gen_seq_write, + .llseek = seq_lseek, + .release = seq_release, +}; + +static const struct file_operations lru_gen_ro_fops = { + .open = lru_gen_seq_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, +}; + /****************************************************************************** * initialization ******************************************************************************/ @@ -5087,6 +5496,12 @@ static int __init init_lru_gen(void) BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS); BUILD_BUG_ON(sizeof(MM_STAT_CODES) != NR_MM_STATS + 1); + if (sysfs_create_group(mm_kobj, &lru_gen_attr_group)) + pr_err("lru_gen: failed to create sysfs group\n"); + + debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops); + debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops); + return 0; }; late_initcall(init_lru_gen); -- 2.34.1.448.ga2b2bfdf31-goog
