A reaccess refers to detecting an access on a page via refault
or access bit harvesting after the initial access. Similar to
the working set histogram, the reaccess histogram breaks down
reaccesses into user-defined bins.
It tracks reaccesses from MGLRU walks, where a move from older
generations to the young generation counts as a reaccess.
Swapped out pages are tracked with the generation number
encoded in mm/workingset.c, and additional tracking is added
for enabled memory cgroups to track an additional 4 swapped out
generations.
Memcg interfaces:
/sys/fs/cgroup/.../memory.workingset.reaccess
The format is identical to memory.workingset.page_age, but the
content breaks down reaccesses into pre-defined intervals.
e.g.
N0
1000 anon=6330 file=0
2000 anon=72 file=0
4000 anon=0 file=0
18446744073709551615 anon=0 file=0
N1
18446744073709551615 anon=0 file=0
/sys/fs/cgroup/.../memory.workingset.reaccess_intervals
Defines the per-node intervals for memory.workingset.reaccess.
e.g.
echo N0=120000,240000,480000 > memory.workingset.reaccess_intervals
Signed-off-by: Yuanchu Xie <yuanchu@xxxxxxxxxx>
---
include/linux/workingset_report.h | 20 +++
mm/internal.h | 28 ++++
mm/memcontrol.c | 112 ++++++++++++++
mm/vmscan.c | 8 +-
mm/workingset.c | 9 +-
mm/workingset_report.c | 249 ++++++++++++++++++++++++++++++
6 files changed, 419 insertions(+), 7 deletions(-)
diff --git a/include/linux/workingset_report.h b/include/linux/workingset_report.h
index 502542c812b3..e908c5678b1e 100644
--- a/include/linux/workingset_report.h
+++ b/include/linux/workingset_report.h
@@ -4,6 +4,7 @@
#include <linux/types.h>
#include <linux/mutex.h>
+#include <linux/rcutree.h>
struct mem_cgroup;
struct pglist_data;
@@ -19,6 +20,12 @@ struct cgroup_file;
#define WORKINGSET_INTERVAL_MAX ((unsigned long)-1)
#define ANON_AND_FILE 2
+/*
+ * MAX_NR_EVICTED_GENS is set to 4 so we can track the same number of
+ * generations as MGLRU has resident.
+ */
+#define MAX_NR_EVICTED_GENS 4
+
struct wsr_report_bin {
unsigned long idle_age;
unsigned long nr_pages[ANON_AND_FILE];
@@ -35,6 +42,18 @@ struct wsr_page_age_histo {
struct wsr_report_bins bins;
};
+struct wsr_evicted_gen {
+ unsigned long timestamp;
+ int seq;
+};
+
+struct wsr_reaccess_histo {
+ struct rcu_head rcu;
+ /* evicted gens start from min_seq[LRU_GEN_ANON] - 1 */
+ struct wsr_evicted_gen gens[MAX_NR_EVICTED_GENS];
+ struct wsr_report_bins bins;
+};
+
struct wsr_state {
unsigned long report_threshold;
unsigned long refresh_interval;
@@ -47,6 +66,7 @@ struct wsr_state {
/* breakdown of workingset by page age */
struct mutex page_age_lock;
struct wsr_page_age_histo *page_age;
+ struct wsr_reaccess_histo __rcu *reaccess;
};
void wsr_init(struct lruvec *lruvec);
diff --git a/mm/internal.h b/mm/internal.h
index 3730c8399ad4..077340b526e8 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -205,16 +205,44 @@ void putback_lru_page(struct page *page);
void folio_putback_lru(struct folio *folio);
extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason);
+/*
+ * in mm/workingset.c
+ */
+#define WORKINGSET_SHIFT 1
+#define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) + \
+ WORKINGSET_SHIFT + NODES_SHIFT + \
+ MEM_CGROUP_ID_SHIFT)
+#define EVICTION_MASK (~0UL >> EVICTION_SHIFT)
+
#ifdef CONFIG_WORKINGSET_REPORT
/*
* in mm/wsr.c
*/
+void report_lru_gen_eviction(struct lruvec *lruvec, int type, int min_seq);
+void lru_gen_report_reaccess(struct lruvec *lruvec,
+ struct lru_gen_mm_walk *walk);
+void report_reaccess_refault(struct lruvec *lruvec, unsigned long token,
+ int type, int nr_pages);
void notify_workingset(struct mem_cgroup *memcg, struct pglist_data *pgdat);
/* Requires wsr->page_age_lock held */
void wsr_refresh_scan(struct lruvec *lruvec, unsigned long refresh_interval);
int workingset_report_intervals_parse(char *src,
struct wsr_report_bins *bins);
#else
+struct lru_gen_mm_walk;
+static inline void report_lru_gen_eviction(struct lruvec *lruvec, int type,
+ int min_seq)
+{
+}
+static inline void lru_gen_report_reaccess(struct lruvec *lruvec,
+ struct lru_gen_mm_walk *walk)
+{
+}
+static inline void report_reaccess_refault(struct lruvec *lruvec,
+ unsigned long token, int type,
+ int nr_pages)
+{
+}
static inline void notify_workingset(struct mem_cgroup *memcg,
struct pglist_data *pgdat)
{
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 75bda5f7994d..2a39a4445bb7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7108,6 +7108,71 @@ static ssize_t memory_ws_page_age_intervals_write(struct kernfs_open_file *of,
return err;
}
+static int memory_ws_reaccess_intervals_show(struct seq_file *m, void *v)
+{
+ int nid;
+ struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
+
+ for_each_node_state(nid, N_MEMORY) {
+ struct wsr_state *wsr;
+ struct wsr_reaccess_histo *reaccess;
+ int i, nr_bins;
+
+ wsr = &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+ rcu_read_lock();
+ reaccess = rcu_dereference(wsr->reaccess);
+ if (!reaccess)
+ goto unlock;
+ seq_printf(m, "N%d=", nid);
+ nr_bins = reaccess->bins.nr_bins;
+ for (i = 0; i < nr_bins; ++i) {
+ struct wsr_report_bin *bin = &reaccess->bins.bins[i];
+
+ seq_printf(m, "%u", jiffies_to_msecs(bin->idle_age));
+ if (i + 1 < nr_bins)
+ seq_putc(m, ',');
+ }
+ seq_putc(m, ' ');
+unlock:
+ rcu_read_unlock();
+ }
+ seq_putc(m, '\n');
+
+ return 0;
+}
+
+static ssize_t memory_ws_reaccess_intervals_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ unsigned int nid;
+ int err;
+ struct wsr_state *wsr;
+ struct wsr_reaccess_histo *reaccess = NULL, *old;
+ struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+
+ reaccess = kzalloc(sizeof(struct wsr_reaccess_histo), GFP_KERNEL);
+ if (!reaccess)
+ return -ENOMEM;
+
+ err = memory_wsr_interval_parse(of, buf, nbytes, &nid, &reaccess->bins);
+ if (err < 0)
+ goto failed;
+
+ if (err == 0) {
+ kfree(reaccess);
+ reaccess = NULL;
+ }
+
+ wsr = &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+ old = xchg(&wsr->reaccess, reaccess);
+ kfree_rcu(old, rcu);
+ return nbytes;
+failed:
+ kfree(reaccess);
+ return err;
+}
+
static int memory_ws_refresh_interval_show(struct seq_file *m, void *v)
{
int nid;
@@ -7242,6 +7307,42 @@ static int memory_ws_page_age_show(struct seq_file *m, void *v)
return 0;
}
+
+static int memory_ws_reaccess_histogram_show(struct seq_file *m, void *v)
+{
+ int nid;
+ struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
+
+ for_each_node_state(nid, N_MEMORY) {
+ struct wsr_state *wsr =
+ &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+ struct wsr_reaccess_histo *reaccess;
+ struct wsr_report_bin *bin;
+
+ rcu_read_lock();
+ reaccess = rcu_dereference(wsr->reaccess);
+
+ if (!reaccess)
+ goto unlock;
+
+ wsr_refresh_report(wsr, memcg, NODE_DATA(nid));
+
+ seq_printf(m, "N%d\n", nid);
+ for (bin = reaccess->bins.bins;
+ bin->idle_age != WORKINGSET_INTERVAL_MAX; bin++)
+ seq_printf(m, "%u anon=%lu file=%lu\n",
+ jiffies_to_msecs(bin->idle_age),
+ bin->nr_pages[0], bin->nr_pages[1]);
+
+ seq_printf(m, "%lu anon=%lu file=%lu\n", WORKINGSET_INTERVAL_MAX,
+ bin->nr_pages[0], bin->nr_pages[1]);
+
+unlock:
+ rcu_read_unlock();
+ }
+
+ return 0;
+}
#endif
static struct cftype memory_files[] = {
@@ -7337,6 +7438,17 @@ static struct cftype memory_files[] = {
.file_offset = offsetof(struct mem_cgroup, workingset_page_age_file),
.seq_show = memory_ws_page_age_show,
},
+ {
+ .name = "workingset.reaccess_intervals",
+ .flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE,
+ .seq_show = memory_ws_reaccess_intervals_show,
+ .write = memory_ws_reaccess_intervals_write,
+ },
+ {
+ .name = "workingset.reaccess",
+ .flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE,
+ .seq_show = memory_ws_reaccess_histogram_show,
+ },
#endif
{} /* terminate */
};
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c6acd5265b3f..4d9245e2c0d1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3637,6 +3637,7 @@ static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_
mem_cgroup_unlock_pages();
if (walk->batched) {
+ lru_gen_report_reaccess(lruvec, walk);
spin_lock_irq(&lruvec->lru_lock);
reset_batch_size(lruvec, walk);
spin_unlock_irq(&lruvec->lru_lock);
@@ -3709,6 +3710,7 @@ static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap)
}
done:
reset_ctrl_pos(lruvec, type, true);
+ report_lru_gen_eviction(lruvec, type, lrugen->min_seq[type] + 1);
WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1);
return true;
@@ -3750,6 +3752,7 @@ static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap)
continue;
reset_ctrl_pos(lruvec, type, true);
+ report_lru_gen_eviction(lruvec, type, min_seq[type]);
WRITE_ONCE(lrugen->min_seq[type], min_seq[type]);
success = true;
}
@@ -4565,11 +4568,14 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
sc->nr_scanned -= folio_nr_pages(folio);
}
+ walk = current->reclaim_state->mm_walk;
+ if (walk && walk->batched)
+ lru_gen_report_reaccess(lruvec, walk);
+
spin_lock_irq(&lruvec->lru_lock);
move_folios_to_lru(lruvec, &list);
- walk = current->reclaim_state->mm_walk;
if (walk && walk->batched)
reset_batch_size(lruvec, walk);
diff --git a/mm/workingset.c b/mm/workingset.c
index 226012974328..057fbedd91ea 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -17,6 +17,8 @@
#include <linux/fs.h>
#include <linux/mm.h>
+#include "internal.h"
+
/*
* Double CLOCK lists
*
@@ -179,12 +181,6 @@
* refault distance will immediately activate the refaulting page.
*/
-#define WORKINGSET_SHIFT 1
-#define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) + \
- WORKINGSET_SHIFT + NODES_SHIFT + \
- MEM_CGROUP_ID_SHIFT)
-#define EVICTION_MASK (~0UL >> EVICTION_SHIFT)
-
/*
* Eviction timestamps need to be able to cover the full range of
* actionable refaults. However, bits are tight in the xarray
@@ -294,6 +290,7 @@ static void lru_gen_refault(struct folio *folio, void *shadow)
goto unlock;
mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + type, delta);
+ report_reaccess_refault(lruvec, token, type, delta);
if (!recent)
goto unlock;
diff --git a/mm/workingset_report.c b/mm/workingset_report.c
index b00ffbfebcab..504d840bbe6a 100644
--- a/mm/workingset_report.c
+++ b/mm/workingset_report.c
@@ -34,6 +34,7 @@ void wsr_destroy(struct lruvec *lruvec)
mutex_destroy(&wsr->page_age_lock);
kfree(wsr->page_age);
+ kfree_rcu(wsr->reaccess, rcu);
memset(wsr, 0, sizeof(*wsr));
}
@@ -259,6 +260,254 @@ bool wsr_refresh_report(struct wsr_state *wsr, struct mem_cgroup *root,
}
EXPORT_SYMBOL_GPL(wsr_refresh_report);
+static void lru_gen_collect_reaccess_refault(struct wsr_report_bins *bins,
+ unsigned long timestamp, int type,
+ int nr_pages)
+{
+ unsigned long curr_timestamp = jiffies;
+ struct wsr_report_bin *bin = &bins->bins[0];
+
+ while (bin->idle_age != WORKINGSET_INTERVAL_MAX &&
+ time_before(timestamp + bin->idle_age, curr_timestamp))
+ bin++;
+
+ bin->nr_pages[type] += nr_pages;
+}
+
+static void collect_reaccess_type(struct lru_gen_mm_walk *walk,
+ const struct lru_gen_folio *lrugen,
+ struct wsr_report_bin *bin,
+ unsigned long max_seq, unsigned long min_seq,
+ unsigned long curr_timestamp, int type)
+{
+ unsigned long seq;
+
+ /* Skip max_seq because a reaccess moves a page from another seq
+ * to max_seq. We use the negative change in page count from
+ * other seqs to track the number of reaccesses.
+ */
+ for (seq = max_seq - 1; seq + 1 > min_seq; seq--) {
+ int younger_gen, gen, zone;
+ unsigned long gen_end, gen_start;
+ long delta = 0;
+
+ gen = lru_gen_from_seq(seq);
+
+ for (zone = 0; zone < MAX_NR_ZONES; zone++) {
+ long nr_pages = walk->nr_pages[gen][type][zone];
+
+ if (nr_pages < 0)
+ delta += -nr_pages;
+ }
+
+ gen_end = READ_ONCE(lrugen->timestamps[gen]);
+ younger_gen = lru_gen_from_seq(seq + 1);
+ gen_start = READ_ONCE(lrugen->timestamps[younger_gen]);
+
+ /* ensure gen_start is within idle_age of bin */
+ while (bin->idle_age != WORKINGSET_INTERVAL_MAX &&
+ time_before(gen_start + bin->idle_age, curr_timestamp))
+ bin++;
+
+ while (bin->idle_age != WORKINGSET_INTERVAL_MAX &&
+ time_before(gen_end + bin->idle_age, curr_timestamp)) {
+ unsigned long proportion = (long)gen_start -
+ (long)curr_timestamp +
+ (long)bin->idle_age;
+ unsigned long gen_len = (long)gen_start - (long)gen_end;
+
+ if (!gen_len)
+ break;
+ if (proportion) {
+ unsigned long split_bin =
+ delta / gen_len * proportion;
+ bin->nr_pages[type] += split_bin;
+ delta -= split_bin;
+ }
+ gen_start = curr_timestamp - bin->idle_age;
+ bin++;
+ }
+ bin->nr_pages[type] += delta;
+ }
+}
+
+/*
+ * Reaccesses are propagated up the memcg hierarchy during scanning/refault.
+ * Collect the reaccess information from a multi-gen LRU walk.
+ */
+static void lru_gen_collect_reaccess(struct wsr_report_bins *bins,
+ struct lru_gen_folio *lrugen,
+ struct lru_gen_mm_walk *walk)
+{
+ int type;
+ unsigned long curr_timestamp = jiffies;
+ unsigned long max_seq = READ_ONCE(walk->max_seq);
+ unsigned long min_seq[ANON_AND_FILE] = {
+ READ_ONCE(lrugen->min_seq[LRU_GEN_ANON]),
+ READ_ONCE(lrugen->min_seq[LRU_GEN_FILE]),
+ };
+
+ for (type = 0; type < ANON_AND_FILE; type++) {
+ struct wsr_report_bin *bin = &bins->bins[0];
+
+ collect_reaccess_type(walk, lrugen, bin, max_seq,
+ min_seq[type], curr_timestamp, type);
+ }
+}
+
+void lru_gen_report_reaccess(struct lruvec *lruvec, struct lru_gen_mm_walk *walk)
+{
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+
+ for (memcg = lruvec_memcg(lruvec); memcg;
+ memcg = parent_mem_cgroup(memcg)) {
+ struct lruvec *memcg_lruvec =
+ mem_cgroup_lruvec(memcg, lruvec_pgdat(lruvec));
+ struct wsr_state *wsr = &memcg_lruvec->wsr;
+ struct wsr_reaccess_histo *reaccess;
+
+ rcu_read_lock();
+ reaccess = rcu_dereference(wsr->reaccess);
+ if (!reaccess) {
+ rcu_read_unlock();
+ continue;
+ }
+ lru_gen_collect_reaccess(&reaccess->bins, lrugen, walk);
+ rcu_read_unlock();
+ }
+}
+
+static inline int evicted_gen_from_seq(unsigned long seq)
+{
+ return seq % MAX_NR_EVICTED_GENS;
+}
+
+void report_lru_gen_eviction(struct lruvec *lruvec, int type, int min_seq)
+{
+ int seq;
+ struct wsr_reaccess_histo *reaccess = NULL;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ struct wsr_state *wsr = &lruvec->wsr;
+
+ /*
+ * Since file can go ahead of anon, min_seq[file] >= min_seq[anon]
+ * only record evictions when anon moves forward.
+ */
+ if (type != LRU_GEN_ANON)
+ return;
+
+ /*
+ * lru_lock is held during eviction, so reaccess accounting
+ * can be serialized.
+ */
+ lockdep_assert_held(&lruvec->lru_lock);
+
+ rcu_read_lock();
+ reaccess = rcu_dereference(wsr->reaccess);
+ if (!reaccess)
+ goto unlock;
+
+ for (seq = READ_ONCE(lrugen->min_seq[LRU_GEN_ANON]); seq < min_seq;
+ ++seq) {
+ int evicted_gen = evicted_gen_from_seq(seq);
+ int gen = lru_gen_from_seq(seq);
+
+ WRITE_ONCE(reaccess->gens[evicted_gen].seq, seq);
+ WRITE_ONCE(reaccess->gens[evicted_gen].timestamp,
+ READ_ONCE(lrugen->timestamps[gen]));
+ }
+
+unlock:
+ rcu_read_unlock();
+}
+
+/*
+ * May yield an incorrect timestamp if the token collides with
+ * a recently evicted generation.
+ */
+static int timestamp_from_workingset_token(struct lruvec *lruvec,
+ unsigned long token,
+ unsigned long *timestamp)
+{
+ int type, err = -EEXIST;
+ unsigned long seq, evicted_min_seq;
+ struct wsr_reaccess_histo *reaccess = NULL;
+ struct lru_gen_folio *lrugen = &lruvec->lrugen;
+ struct wsr_state *wsr = &lruvec->wsr;
+ unsigned long min_seq[ANON_AND_FILE] = {
+ READ_ONCE(lrugen->min_seq[LRU_GEN_ANON]),
+ READ_ONCE(lrugen->min_seq[LRU_GEN_FILE])
+ };
+
+ token >>= LRU_REFS_WIDTH;
+
+ /* recent eviction */
+ for (type = 0; type < ANON_AND_FILE; ++type) {
+ if (token ==
+ (min_seq[type] & (EVICTION_MASK >> LRU_REFS_WIDTH))) {
+ int gen = lru_gen_from_seq(min_seq[type]);
+
+ *timestamp = READ_ONCE(lrugen->timestamps[gen]);
+ return 0;
+ }
+ }
+
+ rcu_read_lock();
+ reaccess = rcu_dereference(wsr->reaccess);
+ if (!reaccess)
+ goto unlock;
+
+ /* look up in evicted gen buffer */
+ evicted_min_seq = min_seq[LRU_GEN_ANON] - MAX_NR_EVICTED_GENS;
+ if (min_seq[LRU_GEN_ANON] < MAX_NR_EVICTED_GENS)
+ evicted_min_seq = 0;
+ for (seq = min_seq[LRU_GEN_ANON]; seq > evicted_min_seq; --seq) {
+ int gen = evicted_gen_from_seq(seq - 1);
+
+ if (token == (reaccess->gens[gen].seq &
+ (EVICTION_MASK >> LRU_REFS_WIDTH))) {
+ *timestamp = reaccess->gens[gen].timestamp;
+
+ goto unlock;
+ }
+ }
+
+unlock:
+ rcu_read_unlock();
+ return err;
+}
+
+void report_reaccess_refault(struct lruvec *lruvec, unsigned long token,
+ int type, int nr_pages)
+{
+ unsigned long timestamp;
+ int err;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+
+ err = timestamp_from_workingset_token(lruvec, token, ×tamp);
+ if (err)
+ return;
+
+ for (memcg = lruvec_memcg(lruvec); memcg;
+ memcg = parent_mem_cgroup(memcg)) {
+ struct lruvec *memcg_lruvec =
+ mem_cgroup_lruvec(memcg, lruvec_pgdat(lruvec));
+ struct wsr_state *wsr = &memcg_lruvec->wsr;
+ struct wsr_reaccess_histo *reaccess = NULL;
+
+ rcu_read_lock();
+ reaccess = rcu_dereference(wsr->reaccess);
+ if (!reaccess) {
+ rcu_read_unlock();
+ continue;
+ }
+ lru_gen_collect_reaccess_refault(&reaccess->bins, timestamp,
+ type, nr_pages);
+ rcu_read_unlock();
+ }
+}
+
static struct pglist_data *kobj_to_pgdat(struct kobject *kobj)
{
int nid = IS_ENABLED(CONFIG_NUMA) ? kobj_to_dev(kobj)->id :
--
2.44.0.396.g6e790dbe36-goog
