[PATCH -V2 2/3] migrate_pages: move split folios processing out of migrate_pages_batch()
From: Huang Ying
Date: Thu Mar 02 2023 - 22:02:41 EST
To simplify the code logic and reduce the line number.
Fixes: 5dfab109d519 ("migrate_pages: batch _unmap and _move")
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: "Xu, Pengfei" <pengfei.xu@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Stefan Roesch <shr@xxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Xin Hao <xhao@xxxxxxxxxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
mm/migrate.c | 78 +++++++++++++++++++---------------------------------
1 file changed, 28 insertions(+), 50 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index 7d751d6a2c15..61009e2ae2be 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1619,9 +1619,10 @@ static int migrate_hugetlbs(struct list_head *from, new_page_t get_new_page,
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)
+ struct list_head *split_folios, struct migrate_pages_stats *stats,
+ int nr_pass)
{
- int retry;
+ int retry = 1;
int large_retry = 1;
int thp_retry = 1;
int nr_failed = 0;
@@ -1631,21 +1632,15 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
bool is_large = false;
bool is_thp = false;
struct folio *folio, *folio2, *dst = NULL, *dst2;
- int rc, rc_saved, nr_pages;
- LIST_HEAD(split_folios);
+ int rc, rc_saved = 0, nr_pages;
LIST_HEAD(unmap_folios);
LIST_HEAD(dst_folios);
bool nosplit = (reason == MR_NUMA_MISPLACED);
- bool no_split_folio_counting = false;
VM_WARN_ON_ONCE(mode != MIGRATE_ASYNC &&
!list_empty(from) && !list_is_singular(from));
-retry:
- rc_saved = 0;
- retry = 1;
- for (pass = 0;
- pass < NR_MAX_MIGRATE_PAGES_RETRY && (retry || large_retry);
- pass++) {
+
+ for (pass = 0; pass < nr_pass && (retry || large_retry); pass++) {
retry = 0;
large_retry = 0;
thp_retry = 0;
@@ -1676,7 +1671,7 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
if (!thp_migration_supported() && is_thp) {
nr_large_failed++;
stats->nr_thp_failed++;
- if (!try_split_folio(folio, &split_folios)) {
+ if (!try_split_folio(folio, split_folios)) {
stats->nr_thp_split++;
continue;
}
@@ -1708,7 +1703,7 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
stats->nr_thp_failed += is_thp;
/* Large folio NUMA faulting doesn't split to retry. */
if (!nosplit) {
- int ret = try_split_folio(folio, &split_folios);
+ int ret = try_split_folio(folio, split_folios);
if (!ret) {
stats->nr_thp_split += is_thp;
@@ -1725,18 +1720,11 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
break;
}
}
- } else if (!no_split_folio_counting) {
+ } else {
nr_failed++;
}
stats->nr_failed_pages += nr_pages + nr_retry_pages;
- /*
- * There might be some split folios of fail-to-migrate large
- * folios left in split_folios list. Move them to ret_folios
- * list so that they could be put back to the right list by
- * the caller otherwise the folio refcnt will be leaked.
- */
- list_splice_init(&split_folios, ret_folios);
/* nr_failed isn't updated for not used */
nr_large_failed += large_retry;
stats->nr_thp_failed += thp_retry;
@@ -1749,7 +1737,7 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
if (is_large) {
large_retry++;
thp_retry += is_thp;
- } else if (!no_split_folio_counting) {
+ } else {
retry++;
}
nr_retry_pages += nr_pages;
@@ -1772,7 +1760,7 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
if (is_large) {
nr_large_failed++;
stats->nr_thp_failed += is_thp;
- } else if (!no_split_folio_counting) {
+ } else {
nr_failed++;
}
@@ -1790,9 +1778,7 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
try_to_unmap_flush();
retry = 1;
- for (pass = 0;
- pass < NR_MAX_MIGRATE_PAGES_RETRY && (retry || large_retry);
- pass++) {
+ for (pass = 0; pass < nr_pass && (retry || large_retry); pass++) {
retry = 0;
large_retry = 0;
thp_retry = 0;
@@ -1821,7 +1807,7 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
if (is_large) {
large_retry++;
thp_retry += is_thp;
- } else if (!no_split_folio_counting) {
+ } else {
retry++;
}
nr_retry_pages += nr_pages;
@@ -1834,7 +1820,7 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
if (is_large) {
nr_large_failed++;
stats->nr_thp_failed += is_thp;
- } else if (!no_split_folio_counting) {
+ } else {
nr_failed++;
}
@@ -1871,27 +1857,6 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
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 (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.
- */
- list_splice_init(from, ret_folios);
- list_splice_init(&split_folios, from);
- /*
- * Force async mode to avoid to wait lock or bit when we have
- * locked more than one folios.
- */
- mode = MIGRATE_ASYNC;
- no_split_folio_counting = true;
- goto retry;
- }
-
return rc;
}
@@ -1930,6 +1895,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
struct folio *folio, *folio2;
LIST_HEAD(folios);
LIST_HEAD(ret_folios);
+ LIST_HEAD(split_folios);
struct migrate_pages_stats stats;
trace_mm_migrate_pages_start(mode, reason);
@@ -1963,12 +1929,24 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
else
list_splice_init(from, &folios);
rc = migrate_pages_batch(&folios, get_new_page, put_new_page, private,
- mode, reason, &ret_folios, &stats);
+ mode, reason, &ret_folios, &split_folios, &stats,
+ NR_MAX_MIGRATE_PAGES_RETRY);
list_splice_tail_init(&folios, &ret_folios);
if (rc < 0) {
rc_gather = rc;
+ list_splice_tail(&split_folios, &ret_folios);
goto out;
}
+ if (!list_empty(&split_folios)) {
+ /*
+ * Failure isn't counted since all split folios of a large folio
+ * is counted as 1 failure already. And, we only try to migrate
+ * with minimal effort, force MIGRATE_ASYNC mode and retry once.
+ */
+ migrate_pages_batch(&split_folios, get_new_page, put_new_page, private,
+ MIGRATE_ASYNC, reason, &ret_folios, NULL, &stats, 1);
+ list_splice_tail_init(&split_folios, &ret_folios);
+ }
rc_gather += rc;
if (!list_empty(from))
goto again;
--
2.39.2