The patch titled
Subject: mm, swap: reduce contention on device lock
has been added to the -mm mm-unstable branch. Its filename is
mm-swap-reduce-contention-on-device-lock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swap-reduce-contention-on-device-lock.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Kairui Song <kasong@xxxxxxxxxxx>
Subject: mm, swap: reduce contention on device lock
Date: Tue, 31 Dec 2024 01:46:17 +0800
Currently, swap locking is mainly composed of two locks: the cluster lock
(ci->lock) and the device lock (si->lock).
The cluster lock is much more fine-grained, so it is best to use ci->lock
instead of si->lock as much as possible.
We have cleaned up other hard dependencies on si->lock. Following the new
cluster allocator design, most operations don't need to touch si->lock at
all. In practice, we only need to take si->lock when moving clusters
between lists.
To achieve this, this commit reworks the locking pattern of all si->lock
and ci->lock users, eliminates all usage of ci->lock inside si->lock, and
introduces a new design to avoid touching si->lock unless needed.
For minimal contention and easier understanding of the system, two ideas
are introduced with the corresponding helpers: isolation and relocation.
- Clusters will be `isolated` from the list when iterating the list
to search for an allocatable cluster.
This ensures other CPUs won't walk into the same cluster easily,
and it releases si->lock after acquiring ci->lock, providing the
only place that handles the inversion of two locks, and avoids
contention.
Iterating the cluster list almost always moves the cluster
(free -> nonfull, nonfull -> frag, frag -> frag tail), but it
doesn't know where the cluster should be moved to until scanning
is done. So keeping the cluster off-list is a good option with
low overhead.
The off-list time window of a cluster is also minimal. In the worst
case, one CPU will return the cluster after scanning the 512 entries
on it, which we used to busy wait with a spin lock.
This is done with the new helper `cluster_isolate_lock`.
- Clusters will be `relocated` after allocation or freeing, according
to their usage count and status.
Allocations no longer hold si->lock now, and may drop ci->lock for
reclaim, so the cluster could be moved to any location while no lock
is held. Besides, isolation clears all flags when it takes the
cluster off the list (the flags must be in sync with the list status,
so cluster users don't need to touch si->lock for checking its list
status). So the cluster has to be relocated to the right list
according to its usage after allocation or freeing.
Relocation is optional, if the cluster flags indicate it's already
on the right list, it will skip touching the list or si->lock.
This is done with relocate_cluster after allocation or with
[partial_]free_cluster after freeing.
This handled usage of all kinds of clusters in a clean way.
Scanning and allocation by iterating the cluster list is handled by
"isolate - <scan / allocate> - relocate".
Scanning and allocation of per-CPU clusters will only involve
"<scan / allocate> - relocate", as it knows which cluster to lock
and use.
Freeing will only involve "relocate".
Each CPU will keep using its per-CPU cluster until the 512 entries are all
consumed. Freeing also has to free 512 entries to trigger cluster
movement in the best case, so si->lock is rarely touched.
Testing with building the Linux kernel with defconfig showed huge
improvement:
tiem make -j96 / 768M memcg, 4K pages, 10G ZRAM, on Intel 8255C:
Before:
Sys time: 73578.30, Real time: 864.05
After: (-50.7% sys time, -44.8% real time)
Sys time: 36227.49, Real time: 476.66
time make -j96 / 1152M memcg, 64K mTHP, 10G ZRAM, on Intel 8255C:
(avg of 4 test run)
Before:
Sys time: 74044.85, Real time: 846.51
hugepages-64kB/stats/swpout: 1735216
hugepages-64kB/stats/swpout_fallback: 430333
After: (-40.4% sys time, -37.1% real time)
Sys time: 44160.56, Real time: 532.07
hugepages-64kB/stats/swpout: 1786288
hugepages-64kB/stats/swpout_fallback: 243384
time make -j32 / 512M memcg, 4K pages, 5G ZRAM, on AMD 7K62:
Before:
Sys time: 8098.21, Real time: 401.3
After: (-22.6% sys time, -12.8% real time )
Sys time: 6265.02, Real time: 349.83
The allocation success rate also slightly improved as we sanitized the
usage of clusters with new defined helpers, previously dropping si->lock
or ci->lock during scan will cause cluster order shuffle.
Link: https://lkml.kernel.org/r/20241230174621.61185-10-ryncsn@xxxxxxxxx
Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
Suggested-by: Chris Li <chrisl@xxxxxxxxxx>
Cc: Barry Song <v-songbaohua@xxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 3
mm/swapfile.c | 435 ++++++++++++++++++++++-------------------
2 files changed, 246 insertions(+), 192 deletions(-)
--- a/include/linux/swap.h~mm-swap-reduce-contention-on-device-lock
+++ a/include/linux/swap.h
@@ -291,6 +291,7 @@ enum swap_cluster_flags {
* throughput.
*/
struct percpu_cluster {
+ local_lock_t lock; /* Protect the percpu_cluster above */
unsigned int next[SWAP_NR_ORDERS]; /* Likely next allocation offset */
};
@@ -313,7 +314,7 @@ struct swap_info_struct {
/* list of cluster that contains at least one free slot */
struct list_head frag_clusters[SWAP_NR_ORDERS];
/* list of cluster that are fragmented or contented */
- unsigned int frag_cluster_nr[SWAP_NR_ORDERS];
+ atomic_long_t frag_cluster_nr[SWAP_NR_ORDERS];
unsigned int pages; /* total of usable pages of swap */
atomic_long_t inuse_pages; /* number of those currently in use */
struct percpu_cluster __percpu *percpu_cluster; /* per cpu's swap location */
--- a/mm/swapfile.c~mm-swap-reduce-contention-on-device-lock
+++ a/mm/swapfile.c
@@ -261,12 +261,10 @@ static int __try_to_reclaim_swap(struct
folio_ref_sub(folio, nr_pages);
folio_set_dirty(folio);
- spin_lock(&si->lock);
/* Only sinple page folio can be backed by zswap */
if (nr_pages == 1)
zswap_invalidate(entry);
swap_entry_range_free(si, entry, nr_pages);
- spin_unlock(&si->lock);
ret = nr_pages;
out_unlock:
folio_unlock(folio);
@@ -403,7 +401,21 @@ static void discard_swap_cluster(struct
static inline bool cluster_is_free(struct swap_cluster_info *info)
{
- return info->flags == CLUSTER_FLAG_FREE;
+ return info->count == 0;
+}
+
+static inline bool cluster_is_discard(struct swap_cluster_info *info)
+{
+ return info->flags == CLUSTER_FLAG_DISCARD;
+}
+
+static inline bool cluster_is_usable(struct swap_cluster_info *ci, int order)
+{
+ if (unlikely(ci->flags > CLUSTER_FLAG_USABLE))
+ return false;
+ if (!order)
+ return true;
+ return cluster_is_free(ci) || order == ci->order;
}
static inline unsigned int cluster_index(struct swap_info_struct *si,
@@ -440,19 +452,20 @@ static void cluster_move(struct swap_inf
{
VM_WARN_ON(ci->flags == new_flags);
BUILD_BUG_ON(1 << sizeof(ci->flags) * BITS_PER_BYTE < CLUSTER_FLAG_MAX);
+ lockdep_assert_held(&ci->lock);
- if (ci->flags == CLUSTER_FLAG_NONE) {
+ spin_lock(&si->lock);
+ if (ci->flags == CLUSTER_FLAG_NONE)
list_add_tail(&ci->list, list);
- } else {
- if (ci->flags == CLUSTER_FLAG_FRAG) {
- VM_WARN_ON(!si->frag_cluster_nr[ci->order]);
- si->frag_cluster_nr[ci->order]--;
- }
+ else
list_move_tail(&ci->list, list);
- }
+ spin_unlock(&si->lock);
+
+ if (ci->flags == CLUSTER_FLAG_FRAG)
+ atomic_long_dec(&si->frag_cluster_nr[ci->order]);
+ else if (new_flags == CLUSTER_FLAG_FRAG)
+ atomic_long_inc(&si->frag_cluster_nr[ci->order]);
ci->flags = new_flags;
- if (new_flags == CLUSTER_FLAG_FRAG)
- si->frag_cluster_nr[ci->order]++;
}
/* Add a cluster to discard list and schedule it to do discard */
@@ -475,39 +488,90 @@ static void swap_cluster_schedule_discar
static void __free_cluster(struct swap_info_struct *si, struct swap_cluster_info *ci)
{
- lockdep_assert_held(&si->lock);
lockdep_assert_held(&ci->lock);
cluster_move(si, ci, &si->free_clusters, CLUSTER_FLAG_FREE);
ci->order = 0;
}
/*
+ * Isolate and lock the first cluster that is not contented on a list,
+ * clean its flag before taken off-list. Cluster flag must be in sync
+ * with list status, so cluster updaters can always know the cluster
+ * list status without touching si lock.
+ *
+ * Note it's possible that all clusters on a list are contented so
+ * this returns NULL for an non-empty list.
+ */
+static struct swap_cluster_info *cluster_isolate_lock(
+ struct swap_info_struct *si, struct list_head *list)
+{
+ struct swap_cluster_info *ci, *ret = NULL;
+
+ spin_lock(&si->lock);
+
+ if (unlikely(!(si->flags & SWP_WRITEOK)))
+ goto out;
+
+ list_for_each_entry(ci, list, list) {
+ if (!spin_trylock(&ci->lock))
+ continue;
+
+ /* We may only isolate and clear flags of following lists */
+ VM_BUG_ON(!ci->flags);
+ VM_BUG_ON(ci->flags > CLUSTER_FLAG_USABLE &&
+ ci->flags != CLUSTER_FLAG_FULL);
+
+ list_del(&ci->list);
+ ci->flags = CLUSTER_FLAG_NONE;
+ ret = ci;
+ break;
+ }
+out:
+ spin_unlock(&si->lock);
+
+ return ret;
+}
+
+/*
* Doing discard actually. After a cluster discard is finished, the cluster
- * will be added to free cluster list. caller should hold si->lock.
-*/
-static void swap_do_scheduled_discard(struct swap_info_struct *si)
+ * will be added to free cluster list. Discard cluster is a bit special as
+ * they don't participate in allocation or reclaim, so clusters marked as
+ * CLUSTER_FLAG_DISCARD must remain off-list or on discard list.
+ */
+static bool swap_do_scheduled_discard(struct swap_info_struct *si)
{
struct swap_cluster_info *ci;
+ bool ret = false;
unsigned int idx;
+ spin_lock(&si->lock);
while (!list_empty(&si->discard_clusters)) {
ci = list_first_entry(&si->discard_clusters, struct swap_cluster_info, list);
+ /*
+ * Delete the cluster from list but don't clear its flags until
+ * discard is done, so isolation and relocation will skip it.
+ */
list_del(&ci->list);
- /* Must clear flag when taking a cluster off-list */
- ci->flags = CLUSTER_FLAG_NONE;
idx = cluster_index(si, ci);
spin_unlock(&si->lock);
-
discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
SWAPFILE_CLUSTER);
- spin_lock(&si->lock);
spin_lock(&ci->lock);
- __free_cluster(si, ci);
+ /*
+ * Discard is done, clear its flags as it's now off-list,
+ * then return the cluster to allocation list.
+ */
+ ci->flags = CLUSTER_FLAG_NONE;
memset(si->swap_map + idx * SWAPFILE_CLUSTER,
0, SWAPFILE_CLUSTER);
+ __free_cluster(si, ci);
spin_unlock(&ci->lock);
+ ret = true;
+ spin_lock(&si->lock);
}
+ spin_unlock(&si->lock);
+ return ret;
}
static void swap_discard_work(struct work_struct *work)
@@ -516,9 +580,7 @@ static void swap_discard_work(struct wor
si = container_of(work, struct swap_info_struct, discard_work);
- spin_lock(&si->lock);
swap_do_scheduled_discard(si);
- spin_unlock(&si->lock);
}
static void swap_users_ref_free(struct percpu_ref *ref)
@@ -529,10 +591,14 @@ static void swap_users_ref_free(struct p
complete(&si->comp);
}
+/*
+ * Must be called after freeing if ci->count == 0, moves the cluster to free
+ * or discard list.
+ */
static void free_cluster(struct swap_info_struct *si, struct swap_cluster_info *ci)
{
VM_BUG_ON(ci->count != 0);
- lockdep_assert_held(&si->lock);
+ VM_BUG_ON(ci->flags == CLUSTER_FLAG_FREE);
lockdep_assert_held(&ci->lock);
/*
@@ -550,6 +616,48 @@ static void free_cluster(struct swap_inf
}
/*
+ * Must be called after freeing if ci->count != 0, moves the cluster to
+ * nonfull list.
+ */
+static void partial_free_cluster(struct swap_info_struct *si,
+ struct swap_cluster_info *ci)
+{
+ VM_BUG_ON(!ci->count || ci->count == SWAPFILE_CLUSTER);
+ lockdep_assert_held(&ci->lock);
+
+ if (ci->flags != CLUSTER_FLAG_NONFULL)
+ cluster_move(si, ci, &si->nonfull_clusters[ci->order],
+ CLUSTER_FLAG_NONFULL);
+}
+
+/*
+ * Must be called after allocation, moves the cluster to full or frag list.
+ * Note: allocation doesn't acquire si lock, and may drop the ci lock for
+ * reclaim, so the cluster could be any where when called.
+ */
+static void relocate_cluster(struct swap_info_struct *si,
+ struct swap_cluster_info *ci)
+{
+ lockdep_assert_held(&ci->lock);
+
+ /* Discard cluster must remain off-list or on discard list */
+ if (cluster_is_discard(ci))
+ return;
+
+ if (!ci->count) {
+ free_cluster(si, ci);
+ } else if (ci->count != SWAPFILE_CLUSTER) {
+ if (ci->flags != CLUSTER_FLAG_FRAG)
+ cluster_move(si, ci, &si->frag_clusters[ci->order],
+ CLUSTER_FLAG_FRAG);
+ } else {
+ if (ci->flags != CLUSTER_FLAG_FULL)
+ cluster_move(si, ci, &si->full_clusters,
+ CLUSTER_FLAG_FULL);
+ }
+}
+
+/*
* The cluster corresponding to page_nr will be used. The cluster will not be
* added to free cluster list and its usage counter will be increased by 1.
* Only used for initialization.
@@ -567,30 +675,6 @@ static void inc_cluster_info_page(struct
VM_BUG_ON(ci->flags);
}
-/*
- * The cluster ci decreases @nr_pages usage. If the usage counter becomes 0,
- * which means no page in the cluster is in use, we can optionally discard
- * the cluster and add it to free cluster list.
- */
-static void dec_cluster_info_page(struct swap_info_struct *si,
- struct swap_cluster_info *ci, int nr_pages)
-{
- VM_BUG_ON(ci->count < nr_pages);
- VM_BUG_ON(cluster_is_free(ci));
- lockdep_assert_held(&si->lock);
- lockdep_assert_held(&ci->lock);
- ci->count -= nr_pages;
-
- if (!ci->count) {
- free_cluster(si, ci);
- return;
- }
-
- if (ci->flags != CLUSTER_FLAG_NONFULL)
- cluster_move(si, ci, &si->nonfull_clusters[ci->order],
- CLUSTER_FLAG_NONFULL);
-}
-
static bool cluster_reclaim_range(struct swap_info_struct *si,
struct swap_cluster_info *ci,
unsigned long start, unsigned long end)
@@ -600,8 +684,6 @@ static bool cluster_reclaim_range(struct
int nr_reclaim;
spin_unlock(&ci->lock);
- spin_unlock(&si->lock);
-
do {
switch (READ_ONCE(map[offset])) {
case 0:
@@ -619,9 +701,7 @@ static bool cluster_reclaim_range(struct
}
} while (offset < end);
out:
- spin_lock(&si->lock);
spin_lock(&ci->lock);
-
/*
* Recheck the range no matter reclaim succeeded or not, the slot
* could have been be freed while we are not holding the lock.
@@ -635,11 +715,11 @@ out:
static bool cluster_scan_range(struct swap_info_struct *si,
struct swap_cluster_info *ci,
- unsigned long start, unsigned int nr_pages)
+ unsigned long start, unsigned int nr_pages,
+ bool *need_reclaim)
{
unsigned long offset, end = start + nr_pages;
unsigned char *map = si->swap_map;
- bool need_reclaim = false;
for (offset = start; offset < end; offset++) {
switch (READ_ONCE(map[offset])) {
@@ -648,16 +728,13 @@ static bool cluster_scan_range(struct sw
case SWAP_HAS_CACHE:
if (!vm_swap_full())
return false;
- need_reclaim = true;
+ *need_reclaim = true;
continue;
default:
return false;
}
}
- if (need_reclaim)
- return cluster_reclaim_range(si, ci, start, end);
-
return true;
}
@@ -672,23 +749,13 @@ static bool cluster_alloc_range(struct s
if (!(si->flags & SWP_WRITEOK))
return false;
- VM_BUG_ON(ci->flags == CLUSTER_FLAG_NONE);
- VM_BUG_ON(ci->flags > CLUSTER_FLAG_USABLE);
-
- if (cluster_is_free(ci)) {
- if (nr_pages < SWAPFILE_CLUSTER)
- cluster_move(si, ci, &si->nonfull_clusters[order],
- CLUSTER_FLAG_NONFULL);
+ if (cluster_is_free(ci))
ci->order = order;
- }
memset(si->swap_map + start, usage, nr_pages);
swap_range_alloc(si, nr_pages);
ci->count += nr_pages;
- if (ci->count == SWAPFILE_CLUSTER)
- cluster_move(si, ci, &si->full_clusters, CLUSTER_FLAG_FULL);
-
return true;
}
@@ -699,37 +766,55 @@ static unsigned int alloc_swap_scan_clus
unsigned long start = offset & ~(SWAPFILE_CLUSTER - 1);
unsigned long end = min(start + SWAPFILE_CLUSTER, si->max);
unsigned int nr_pages = 1 << order;
+ bool need_reclaim, ret;
struct swap_cluster_info *ci;
- if (end < nr_pages)
- return SWAP_NEXT_INVALID;
- end -= nr_pages;
+ ci = &si->cluster_info[offset / SWAPFILE_CLUSTER];
+ lockdep_assert_held(&ci->lock);
- ci = lock_cluster(si, offset);
- if (ci->count + nr_pages > SWAPFILE_CLUSTER) {
+ if (end < nr_pages || ci->count + nr_pages > SWAPFILE_CLUSTER) {
offset = SWAP_NEXT_INVALID;
- goto done;
+ goto out;
}
- while (offset <= end) {
- if (cluster_scan_range(si, ci, offset, nr_pages)) {
- if (!cluster_alloc_range(si, ci, offset, usage, order)) {
- offset = SWAP_NEXT_INVALID;
- goto done;
- }
- *foundp = offset;
- if (ci->count == SWAPFILE_CLUSTER) {
+ for (end -= nr_pages; offset <= end; offset += nr_pages) {
+ need_reclaim = false;
+ if (!cluster_scan_range(si, ci, offset, nr_pages, &need_reclaim))
+ continue;
+ if (need_reclaim) {
+ ret = cluster_reclaim_range(si, ci, start, end);
+ /*
+ * Reclaim drops ci->lock and cluster could be used
+ * by another order. Not checking flag as off-list
+ * cluster has no flag set, and change of list
+ * won't cause fragmentation.
+ */
+ if (!cluster_is_usable(ci, order)) {
offset = SWAP_NEXT_INVALID;
- goto done;
+ goto out;
}
- offset += nr_pages;
- break;
+ if (cluster_is_free(ci))
+ offset = start;
+ /* Reclaim failed but cluster is usable, try next */
+ if (!ret)
+ continue;
+ }
+ if (!cluster_alloc_range(si, ci, offset, usage, order)) {
+ offset = SWAP_NEXT_INVALID;
+ goto out;
+ }
+ *foundp = offset;
+ if (ci->count == SWAPFILE_CLUSTER) {
+ offset = SWAP_NEXT_INVALID;
+ goto out;
}
offset += nr_pages;
+ break;
}
if (offset > end)
offset = SWAP_NEXT_INVALID;
-done:
+out:
+ relocate_cluster(si, ci);
unlock_cluster(ci);
return offset;
}
@@ -746,18 +831,17 @@ static void swap_reclaim_full_clusters(s
if (force)
to_scan = swap_usage_in_pages(si) / SWAPFILE_CLUSTER;
- while (!list_empty(&si->full_clusters)) {
- ci = list_first_entry(&si->full_clusters, struct swap_cluster_info, list);
- list_move_tail(&ci->list, &si->full_clusters);
+ while ((ci = cluster_isolate_lock(si, &si->full_clusters))) {
offset = cluster_offset(si, ci);
end = min(si->max, offset + SWAPFILE_CLUSTER);
to_scan--;
- spin_unlock(&si->lock);
while (offset < end) {
if (READ_ONCE(map[offset]) == SWAP_HAS_CACHE) {
+ spin_unlock(&ci->lock);
nr_reclaim = __try_to_reclaim_swap(si, offset,
TTRS_ANYWAY | TTRS_DIRECT);
+ spin_lock(&ci->lock);
if (nr_reclaim) {
offset += abs(nr_reclaim);
continue;
@@ -765,8 +849,8 @@ static void swap_reclaim_full_clusters(s
}
offset++;
}
- spin_lock(&si->lock);
+ unlock_cluster(ci);
if (to_scan <= 0)
break;
}
@@ -778,9 +862,7 @@ static void swap_reclaim_work(struct wor
si = container_of(work, struct swap_info_struct, reclaim_work);
- spin_lock(&si->lock);
swap_reclaim_full_clusters(si, true);
- spin_unlock(&si->lock);
}
/*
@@ -791,29 +873,34 @@ static void swap_reclaim_work(struct wor
static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int order,
unsigned char usage)
{
- struct percpu_cluster *cluster;
struct swap_cluster_info *ci;
unsigned int offset, found = 0;
-new_cluster:
- lockdep_assert_held(&si->lock);
- cluster = this_cpu_ptr(si->percpu_cluster);
- offset = cluster->next[order];
+ /* Fast path using per CPU cluster */
+ local_lock(&si->percpu_cluster->lock);
+ offset = __this_cpu_read(si->percpu_cluster->next[order]);
if (offset) {
- offset = alloc_swap_scan_cluster(si, offset, &found, order, usage);
+ ci = lock_cluster(si, offset);
+ /* Cluster could have been used by another order */
+ if (cluster_is_usable(ci, order)) {
+ if (cluster_is_free(ci))
+ offset = cluster_offset(si, ci);
+ offset = alloc_swap_scan_cluster(si, offset, &found,
+ order, usage);
+ } else {
+ unlock_cluster(ci);
+ }
if (found)
goto done;
}
- if (!list_empty(&si->free_clusters)) {
- ci = list_first_entry(&si->free_clusters, struct swap_cluster_info, list);
- offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci), &found, order, usage);
- /*
- * Either we didn't touch the cluster due to swapoff,
- * or the allocation must success.
- */
- VM_BUG_ON((si->flags & SWP_WRITEOK) && !found);
- goto done;
+new_cluster:
+ ci = cluster_isolate_lock(si, &si->free_clusters);
+ if (ci) {
+ offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
+ &found, order, usage);
+ if (found)
+ goto done;
}
/* Try reclaim from full clusters if free clusters list is drained */
@@ -821,49 +908,45 @@ new_cluster:
swap_reclaim_full_clusters(si, false);
if (order < PMD_ORDER) {
- unsigned int frags = 0;
+ unsigned int frags = 0, frags_existing;
- while (!list_empty(&si->nonfull_clusters[order])) {
- ci = list_first_entry(&si->nonfull_clusters[order],
- struct swap_cluster_info, list);
- cluster_move(si, ci, &si->frag_clusters[order], CLUSTER_FLAG_FRAG);
+ while ((ci = cluster_isolate_lock(si, &si->nonfull_clusters[order]))) {
offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
&found, order, usage);
- frags++;
+ /*
+ * With `fragmenting` set to true, it will surely take
+ * the cluster off nonfull list
+ */
if (found)
goto done;
+ frags++;
}
- /*
- * Nonfull clusters are moved to frag tail if we reached
- * here, count them too, don't over scan the frag list.
- */
- while (frags < si->frag_cluster_nr[order]) {
- ci = list_first_entry(&si->frag_clusters[order],
- struct swap_cluster_info, list);
+ frags_existing = atomic_long_read(&si->frag_cluster_nr[order]);
+ while (frags < frags_existing &&
+ (ci = cluster_isolate_lock(si, &si->frag_clusters[order]))) {
+ atomic_long_dec(&si->frag_cluster_nr[order]);
/*
- * Rotate the frag list to iterate, they were all failing
- * high order allocation or moved here due to per-CPU usage,
- * this help keeping usable cluster ahead.
+ * Rotate the frag list to iterate, they were all
+ * failing high order allocation or moved here due to
+ * per-CPU usage, but they could contain newly released
+ * reclaimable (eg. lazy-freed swap cache) slots.
*/
- list_move_tail(&ci->list, &si->frag_clusters[order]);
offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
&found, order, usage);
- frags++;
if (found)
goto done;
+ frags++;
}
}
- if (!list_empty(&si->discard_clusters)) {
- /*
- * we don't have free cluster but have some clusters in
- * discarding, do discard now and reclaim them, then
- * reread cluster_next_cpu since we dropped si->lock
- */
- swap_do_scheduled_discard(si);
+ /*
+ * We don't have free cluster but have some clusters in
+ * discarding, do discard now and reclaim them, then
+ * reread cluster_next_cpu since we dropped si->lock
+ */
+ if ((si->flags & SWP_PAGE_DISCARD) && swap_do_scheduled_discard(si))
goto new_cluster;
- }
if (order)
goto done;
@@ -874,26 +957,25 @@ new_cluster:
* Clusters here have at least one usable slots and can't fail order 0
* allocation, but reclaim may drop si->lock and race with another user.
*/
- while (!list_empty(&si->frag_clusters[o])) {
- ci = list_first_entry(&si->frag_clusters[o],
- struct swap_cluster_info, list);
+ while ((ci = cluster_isolate_lock(si, &si->frag_clusters[o]))) {
+ atomic_long_dec(&si->frag_cluster_nr[o]);
offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
- &found, 0, usage);
+ &found, order, usage);
if (found)
goto done;
}
- while (!list_empty(&si->nonfull_clusters[o])) {
- ci = list_first_entry(&si->nonfull_clusters[o],
- struct swap_cluster_info, list);
+ while ((ci = cluster_isolate_lock(si, &si->nonfull_clusters[o]))) {
offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
- &found, 0, usage);
+ &found, order, usage);
if (found)
goto done;
}
}
done:
- cluster->next[order] = offset;
+ __this_cpu_write(si->percpu_cluster->next[order], offset);
+ local_unlock(&si->percpu_cluster->lock);
+
return found;
}
@@ -1157,14 +1239,11 @@ start_over:
plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
spin_unlock(&swap_avail_lock);
if (get_swap_device_info(si)) {
- spin_lock(&si->lock);
n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
n_goal, swp_entries, order);
- spin_unlock(&si->lock);
put_swap_device(si);
if (n_ret || size > 1)
goto check_out;
- cond_resched();
}
spin_lock(&swap_avail_lock);
@@ -1377,9 +1456,7 @@ static bool __swap_entries_free(struct s
if (!has_cache) {
for (i = 0; i < nr; i++)
zswap_invalidate(swp_entry(si->type, offset + i));
- spin_lock(&si->lock);
swap_entry_range_free(si, entry, nr);
- spin_unlock(&si->lock);
}
return has_cache;
@@ -1408,16 +1485,27 @@ static void swap_entry_range_free(struct
unsigned char *map_end = map + nr_pages;
struct swap_cluster_info *ci;
+ /* It should never free entries across different clusters */
+ VM_BUG_ON((offset / SWAPFILE_CLUSTER) != ((offset + nr_pages - 1) / SWAPFILE_CLUSTER));
+
ci = lock_cluster(si, offset);
+ VM_BUG_ON(cluster_is_free(ci));
+ VM_BUG_ON(ci->count < nr_pages);
+
+ ci->count -= nr_pages;
do {
VM_BUG_ON(*map != SWAP_HAS_CACHE);
*map = 0;
} while (++map < map_end);
- dec_cluster_info_page(si, ci, nr_pages);
- unlock_cluster(ci);
mem_cgroup_uncharge_swap(entry, nr_pages);
swap_range_free(si, offset, nr_pages);
+
+ if (!ci->count)
+ free_cluster(si, ci);
+ else
+ partial_free_cluster(si, ci);
+ unlock_cluster(ci);
}
static void cluster_swap_free_nr(struct swap_info_struct *si,
@@ -1489,9 +1577,7 @@ void put_swap_folio(struct folio *folio,
ci = lock_cluster(si, offset);
if (size > 1 && swap_is_has_cache(si, offset, size)) {
unlock_cluster(ci);
- spin_lock(&si->lock);
swap_entry_range_free(si, entry, size);
- spin_unlock(&si->lock);
return;
}
for (int i = 0; i < size; i++, entry.val++) {
@@ -1506,46 +1592,19 @@ void put_swap_folio(struct folio *folio,
unlock_cluster(ci);
}
-static int swp_entry_cmp(const void *ent1, const void *ent2)
-{
- const swp_entry_t *e1 = ent1, *e2 = ent2;
-
- return (int)swp_type(*e1) - (int)swp_type(*e2);
-}
-
void swapcache_free_entries(swp_entry_t *entries, int n)
{
- struct swap_info_struct *si, *prev;
int i;
+ struct swap_info_struct *si = NULL;
if (n <= 0)
return;
- prev = NULL;
- si = NULL;
-
- /*
- * Sort swap entries by swap device, so each lock is only taken once.
- * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
- * so low that it isn't necessary to optimize further.
- */
- if (nr_swapfiles > 1)
- sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
for (i = 0; i < n; ++i) {
si = _swap_info_get(entries[i]);
-
- if (si != prev) {
- if (prev != NULL)
- spin_unlock(&prev->lock);
- if (si != NULL)
- spin_lock(&si->lock);
- }
if (si)
swap_entry_range_free(si, entries[i], 1);
- prev = si;
}
- if (si)
- spin_unlock(&si->lock);
}
int __swap_count(swp_entry_t entry)
@@ -1797,13 +1856,8 @@ swp_entry_t get_swap_page_of_type(int ty
goto fail;
/* This is called for allocating swap entry, not cache */
- if (get_swap_device_info(si)) {
- spin_lock(&si->lock);
- if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry, 0))
- atomic_long_dec(&nr_swap_pages);
- spin_unlock(&si->lock);
- put_swap_device(si);
- }
+ if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry, 0))
+ atomic_long_dec(&nr_swap_pages);
fail:
return entry;
}
@@ -3141,6 +3195,7 @@ static struct swap_cluster_info *setup_c
cluster = per_cpu_ptr(si->percpu_cluster, cpu);
for (i = 0; i < SWAP_NR_ORDERS; i++)
cluster->next[i] = SWAP_NEXT_INVALID;
+ local_lock_init(&cluster->lock);
}
/*
@@ -3164,7 +3219,7 @@ static struct swap_cluster_info *setup_c
for (i = 0; i < SWAP_NR_ORDERS; i++) {
INIT_LIST_HEAD(&si->nonfull_clusters[i]);
INIT_LIST_HEAD(&si->frag_clusters[i]);
- si->frag_cluster_nr[i] = 0;
+ atomic_long_set(&si->frag_cluster_nr[i], 0);
}
/*
@@ -3646,7 +3701,6 @@ int add_swap_count_continuation(swp_entr
*/
goto outer;
}
- spin_lock(&si->lock);
offset = swp_offset(entry);
@@ -3711,7 +3765,6 @@ out_unlock_cont:
spin_unlock(&si->cont_lock);
out:
unlock_cluster(ci);
- spin_unlock(&si->lock);
put_swap_device(si);
outer:
if (page)
_
Patches currently in -mm which might be from kasong@xxxxxxxxxxx are
mm-list_lru-fix-false-warning-of-negative-counter.patch
mm-madvise-fix-potential-workingset-node-list_lru-leaks.patch
mm-memcontrol-avoid-duplicated-memcg-enable-check.patch
mm-swap_cgroup-remove-swap_cgroup_cmpxchg.patch
mm-swap_cgroup-remove-global-swap-cgroup-lock.patch
mm-swap_cgroup-decouple-swap-cgroup-recording-and-clearing.patch
mm-swap-minor-clean-up-for-swap-entry-allocation.patch
mm-swap-fold-swap_info_get_cont-in-the-only-caller.patch
mm-swap-remove-old-allocation-path-for-hdd.patch
mm-swap-use-cluster-lock-for-hdd.patch
mm-swap-clean-up-device-availability-check.patch
mm-swap-clean-up-plist-removal-and-adding.patch
mm-swap-hold-a-reference-during-scan-and-cleanup-flag-usage.patch
mm-swap-use-an-enum-to-define-all-cluster-flags-and-wrap-flags-changes.patch
mm-swap-reduce-contention-on-device-lock.patch
mm-swap-simplify-percpu-cluster-updating.patch
mm-swap-introduce-a-helper-for-retrieving-cluster-from-offset.patch
mm-swap-use-a-global-swap-cluster-for-non-rotation-devices.patch
mm-swap_slots-remove-slot-cache-for-freeing-path.patch
