The patch titled
Subject: migrate_pages: batch _unmap and _move
has been added to the -mm mm-unstable branch. Its filename is
migrate_pages-batch-_unmap-and-_move.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/migrate_pages-batch-_unmap-and-_move.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: Huang Ying <ying.huang@xxxxxxxxx>
Subject: migrate_pages: batch _unmap and _move
Date: Mon, 13 Feb 2023 20:34:40 +0800
In this patch the _unmap and _move stage of the folio migration is
batched. That for, previously, it is,
for each folio
_unmap()
_move()
Now, it is,
for each folio
_unmap()
for each folio
_move()
Based on this, we can batch the TLB flushing and use some hardware
accelerator to copy folios between batched _unmap and batched _move
stages.
Link: https://lkml.kernel.org/r/20230213123444.155149-6-ying.huang@xxxxxxxxx
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Tested-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Bharata B Rao <bharata@xxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Xin Hao <xhao@xxxxxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/migrate.c~migrate_pages-batch-_unmap-and-_move
+++ a/mm/migrate.c
@@ -1051,6 +1051,33 @@ static void __migrate_folio_extract(stru
dst->private = NULL;
}
+/* Restore the source folio to the original state upon failure */
+static void migrate_folio_undo_src(struct folio *src,
+ int page_was_mapped,
+ struct anon_vma *anon_vma,
+ struct list_head *ret)
+{
+ if (page_was_mapped)
+ remove_migration_ptes(src, src, false);
+ /* Drop an anon_vma reference if we took one */
+ if (anon_vma)
+ put_anon_vma(anon_vma);
+ folio_unlock(src);
+ list_move_tail(&src->lru, ret);
+}
+
+/* Restore the destination folio to the original state upon failure */
+static void migrate_folio_undo_dst(struct folio *dst,
+ free_page_t put_new_page,
+ unsigned long private)
+{
+ folio_unlock(dst);
+ if (put_new_page)
+ put_new_page(&dst->page, private);
+ else
+ folio_put(dst);
+}
+
/* Cleanup src folio upon migration success */
static void migrate_folio_done(struct folio *src,
enum migrate_reason reason)
@@ -1069,8 +1096,8 @@ static void migrate_folio_done(struct fo
folio_put(src);
}
-static int __migrate_folio_unmap(struct folio *src, struct folio *dst,
- int force, enum migrate_mode mode)
+static int __migrate_folio_unmap(struct folio *src, struct folio *dst, int force,
+ bool avoid_force_lock, enum migrate_mode mode)
{
int rc = -EAGAIN;
int page_was_mapped = 0;
@@ -1097,6 +1124,17 @@ static int __migrate_folio_unmap(struct
if (current->flags & PF_MEMALLOC)
goto out;
+ /*
+ * We have locked some folios and are going to wait to lock
+ * this folio. To avoid a potential deadlock, let's bail
+ * out and not do that. The locked folios will be moved and
+ * unlocked, then we can wait to lock this folio.
+ */
+ if (avoid_force_lock) {
+ rc = -EDEADLOCK;
+ goto out;
+ }
+
folio_lock(src);
}
@@ -1205,10 +1243,20 @@ static int __migrate_folio_move(struct f
int page_was_mapped = 0;
struct anon_vma *anon_vma = NULL;
bool is_lru = !__PageMovable(&src->page);
+ struct list_head *prev;
__migrate_folio_extract(dst, &page_was_mapped, &anon_vma);
+ prev = dst->lru.prev;
+ list_del(&dst->lru);
rc = move_to_new_folio(dst, src, mode);
+
+ if (rc == -EAGAIN) {
+ list_add(&dst->lru, prev);
+ __migrate_folio_record(dst, page_was_mapped, anon_vma);
+ return rc;
+ }
+
if (unlikely(!is_lru))
goto out_unlock_both;
@@ -1251,7 +1299,7 @@ out_unlock_both:
/* Obtain the lock on page, remove all ptes. */
static int migrate_folio_unmap(new_page_t get_new_page, free_page_t put_new_page,
unsigned long private, struct folio *src,
- struct folio **dstp, int force,
+ struct folio **dstp, int force, bool avoid_force_lock,
enum migrate_mode mode, enum migrate_reason reason,
struct list_head *ret)
{
@@ -1279,7 +1327,7 @@ static int migrate_folio_unmap(new_page_
*dstp = dst;
dst->private = NULL;
- rc = __migrate_folio_unmap(src, dst, force, mode);
+ rc = __migrate_folio_unmap(src, dst, force, avoid_force_lock, mode);
if (rc == MIGRATEPAGE_UNMAP)
return rc;
@@ -1287,7 +1335,7 @@ static int migrate_folio_unmap(new_page_
* A folio that has not been unmapped will be restored to
* right list unless we want to retry.
*/
- if (rc != -EAGAIN)
+ if (rc != -EAGAIN && rc != -EDEADLOCK)
list_move_tail(&src->lru, ret);
if (put_new_page)
@@ -1326,9 +1374,8 @@ static int migrate_folio_move(free_page_
*/
if (rc == MIGRATEPAGE_SUCCESS) {
migrate_folio_done(src, reason);
- } else {
- if (rc != -EAGAIN)
- list_add_tail(&src->lru, ret);
+ } else if (rc != -EAGAIN) {
+ list_add_tail(&src->lru, ret);
if (put_new_page)
put_new_page(&dst->page, private);
@@ -1603,12 +1650,16 @@ static int migrate_hugetlbs(struct list_
return nr_failed;
}
+/*
+ * migrate_pages_batch() first unmaps folios in the from list as many as
+ * possible, then move the unmapped folios.
+ */
static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
free_page_t put_new_page, unsigned long private,
enum migrate_mode mode, int reason, struct list_head *ret_folios,
struct migrate_pages_stats *stats)
{
- int retry = 1;
+ int retry;
int large_retry = 1;
int thp_retry = 1;
int nr_failed = 0;
@@ -1617,13 +1668,19 @@ static int migrate_pages_batch(struct li
int pass = 0;
bool is_large = false;
bool is_thp = false;
- struct folio *folio, *folio2, *dst = NULL;
- int rc, nr_pages;
+ struct folio *folio, *folio2, *dst = NULL, *dst2;
+ int rc, rc_saved, nr_pages;
LIST_HEAD(split_folios);
+ LIST_HEAD(unmap_folios);
+ LIST_HEAD(dst_folios);
bool nosplit = (reason == MR_NUMA_MISPLACED);
bool no_split_folio_counting = false;
+ bool avoid_force_lock;
-split_folio_migration:
+retry:
+ rc_saved = 0;
+ avoid_force_lock = false;
+ retry = 1;
for (pass = 0;
pass < NR_MAX_MIGRATE_PAGES_RETRY && (retry || large_retry);
pass++) {
@@ -1645,16 +1702,15 @@ split_folio_migration:
cond_resched();
rc = migrate_folio_unmap(get_new_page, put_new_page, private,
- folio, &dst, pass > 2, mode,
- reason, ret_folios);
- if (rc == MIGRATEPAGE_UNMAP)
- rc = migrate_folio_move(put_new_page, private,
- folio, dst, mode,
- reason, ret_folios);
+ folio, &dst, pass > 2, avoid_force_lock,
+ mode, reason, ret_folios);
/*
* The rules are:
* Success: folio will be freed
+ * Unmap: folio will be put on unmap_folios list,
+ * dst folio put on dst_folios list
* -EAGAIN: stay on the from list
+ * -EDEADLOCK: stay on the from list
* -ENOMEM: stay on the from list
* -ENOSYS: stay on the from list
* Other errno: put on ret_folios list
@@ -1689,7 +1745,7 @@ split_folio_migration:
case -ENOMEM:
/*
* When memory is low, don't bother to try to migrate
- * other folios, just exit.
+ * other folios, move unmapped folios, then exit.
*/
if (is_large) {
nr_large_failed++;
@@ -1728,7 +1784,19 @@ split_folio_migration:
/* nr_failed isn't updated for not used */
nr_large_failed += large_retry;
stats->nr_thp_failed += thp_retry;
- goto out;
+ rc_saved = rc;
+ if (list_empty(&unmap_folios))
+ goto out;
+ else
+ goto move;
+ case -EDEADLOCK:
+ /*
+ * The folio cannot be locked for potential deadlock.
+ * Go move (and unlock) all locked folios. Then we can
+ * try again.
+ */
+ rc_saved = rc;
+ goto move;
case -EAGAIN:
if (is_large) {
large_retry++;
@@ -1742,6 +1810,15 @@ split_folio_migration:
stats->nr_succeeded += nr_pages;
stats->nr_thp_succeeded += is_thp;
break;
+ case MIGRATEPAGE_UNMAP:
+ /*
+ * We have locked some folios, don't force lock
+ * to avoid deadlock.
+ */
+ avoid_force_lock = true;
+ list_move_tail(&folio->lru, &unmap_folios);
+ list_add_tail(&dst->lru, &dst_folios);
+ break;
default:
/*
* Permanent failure (-EBUSY, etc.):
@@ -1765,12 +1842,95 @@ split_folio_migration:
nr_large_failed += large_retry;
stats->nr_thp_failed += thp_retry;
stats->nr_failed_pages += nr_retry_pages;
+move:
+ retry = 1;
+ for (pass = 0;
+ pass < NR_MAX_MIGRATE_PAGES_RETRY && (retry || large_retry);
+ pass++) {
+ retry = 0;
+ large_retry = 0;
+ thp_retry = 0;
+ nr_retry_pages = 0;
+
+ dst = list_first_entry(&dst_folios, struct folio, lru);
+ dst2 = list_next_entry(dst, lru);
+ list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) {
+ is_large = folio_test_large(folio);
+ is_thp = is_large && folio_test_pmd_mappable(folio);
+ nr_pages = folio_nr_pages(folio);
+
+ cond_resched();
+
+ rc = migrate_folio_move(put_new_page, private,
+ folio, dst, mode,
+ reason, ret_folios);
+ /*
+ * The rules are:
+ * Success: folio will be freed
+ * -EAGAIN: stay on the unmap_folios list
+ * Other errno: put on ret_folios list
+ */
+ switch(rc) {
+ case -EAGAIN:
+ if (is_large) {
+ large_retry++;
+ thp_retry += is_thp;
+ } else if (!no_split_folio_counting) {
+ retry++;
+ }
+ nr_retry_pages += nr_pages;
+ break;
+ case MIGRATEPAGE_SUCCESS:
+ stats->nr_succeeded += nr_pages;
+ stats->nr_thp_succeeded += is_thp;
+ break;
+ default:
+ if (is_large) {
+ nr_large_failed++;
+ stats->nr_thp_failed += is_thp;
+ } else if (!no_split_folio_counting) {
+ nr_failed++;
+ }
+
+ stats->nr_failed_pages += nr_pages;
+ break;
+ }
+ dst = dst2;
+ dst2 = list_next_entry(dst, lru);
+ }
+ }
+ nr_failed += retry;
+ nr_large_failed += large_retry;
+ stats->nr_thp_failed += thp_retry;
+ stats->nr_failed_pages += nr_retry_pages;
+
+ if (rc_saved)
+ rc = rc_saved;
+ else
+ rc = nr_failed + nr_large_failed;
+out:
+ /* Cleanup remaining folios */
+ dst = list_first_entry(&dst_folios, struct folio, lru);
+ dst2 = list_next_entry(dst, lru);
+ list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) {
+ int page_was_mapped = 0;
+ struct anon_vma *anon_vma = NULL;
+
+ __migrate_folio_extract(dst, &page_was_mapped, &anon_vma);
+ migrate_folio_undo_src(folio, page_was_mapped, anon_vma,
+ ret_folios);
+ list_del(&dst->lru);
+ migrate_folio_undo_dst(dst, put_new_page, private);
+ dst = dst2;
+ dst2 = list_next_entry(dst, lru);
+ }
+
/*
* Try to migrate split folios of fail-to-migrate large folios, no
* nr_failed counting in this round, since all split folios of a
* large folio is counted as 1 failure in the first round.
*/
- if (!list_empty(&split_folios)) {
+ if (rc >= 0 && !list_empty(&split_folios)) {
/*
* Move non-migrated folios (after NR_MAX_MIGRATE_PAGES_RETRY
* retries) to ret_folios to avoid migrating them again.
@@ -1778,12 +1938,16 @@ split_folio_migration:
list_splice_init(from, ret_folios);
list_splice_init(&split_folios, from);
no_split_folio_counting = true;
- retry = 1;
- goto split_folio_migration;
+ goto retry;
}
- rc = nr_failed + nr_large_failed;
-out:
+ /*
+ * We have unlocked all locked folios, so we can force lock now, let's
+ * try again.
+ */
+ if (rc == -EDEADLOCK)
+ goto retry;
+
return rc;
}
_
Patches currently in -mm which might be from ying.huang@xxxxxxxxx are
migrate_pages-organize-stats-with-struct-migrate_pages_stats.patch
migrate_pages-separate-hugetlb-folios-migration.patch
migrate_pages-restrict-number-of-pages-to-migrate-in-batch.patch
migrate_pages-split-unmap_and_move-to-_unmap-and-_move.patch
migrate_pages-batch-_unmap-and-_move.patch
migrate_pages-move-migrate_folio_unmap.patch
migrate_pages-share-more-code-between-_unmap-and-_move.patch
migrate_pages-batch-flushing-tlb.patch
migrate_pages-move-thp-hugetlb-migration-support-check-to-simplify-code.patch
