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Subject[PATCH 4/6] mm, migrate: Drop references to successfully migrated pages at the same time
Date
After each migration attempt, putback_lru_page() is used to drop the last
reference to the page. This is fine but it prevents the batching of TLB
flushes because the flush must happen before a free. This patch drops all
the migrated pages at once in preparation for batching the TLB flush.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/migrate.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 85e042686031..82c98c5aa6ed 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -906,7 +906,7 @@ out:
*/
static int unmap_and_move(new_page_t get_new_page, free_page_t put_new_page,
unsigned long private, struct page *page, int force,
- enum migrate_mode mode)
+ enum migrate_mode mode, struct list_head *putback_list)
{
int rc = 0;
int *result = NULL;
@@ -937,7 +937,7 @@ out:
list_del(&page->lru);
dec_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
- putback_lru_page(page);
+ list_add(&page->lru, putback_list);
}

/*
@@ -1086,6 +1086,7 @@ int migrate_pages(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)
{
+ LIST_HEAD(putback_list);
int retry = 1;
int nr_failed = 0;
int nr_succeeded = 0;
@@ -1110,7 +1111,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
pass > 2, mode);
else
rc = unmap_and_move(get_new_page, put_new_page,
- private, page, pass > 2, mode);
+ private, page, pass > 2, mode,
+ &putback_list);

switch(rc) {
case -ENOMEM:
@@ -1135,6 +1137,12 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
}
rc = nr_failed + retry;
out:
+ while (!list_empty(&putback_list)) {
+ page = list_entry(putback_list.prev, struct page, lru);
+ list_del(&page->lru);
+ putback_lru_page(page);
+ }
+
if (nr_succeeded)
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
if (nr_failed)
--
2.1.2


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