mm: migration: allow migration to operate asynchronously and avoid synchronous compaction in the faster path
Migration synchronously waits for writeback if the initial passes fails.
Callers of memory compaction do not necessarily want this behaviour if the
caller is latency sensitive or expects that synchronous migration is not
going to have a significantly better success rate.
This patch adds a sync parameter to migrate_pages() allowing the caller to
indicate if wait_on_page_writeback() is allowed within migration or not.
For reclaim/compaction, try_to_compact_pages() is first called
asynchronously, direct reclaim runs and then try_to_compact_pages() is
called synchronously as there is a greater expectation that it'll succeed.
[akpm@linux-foundation.org: build/merge fix]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/migrate.c b/mm/migrate.c
index 94875b2..dc47f6c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -614,7 +614,7 @@
* to the newly allocated page in newpage.
*/
static int unmap_and_move(new_page_t get_new_page, unsigned long private,
- struct page *page, int force, int offlining)
+ struct page *page, int force, int offlining, bool sync)
{
int rc = 0;
int *result = NULL;
@@ -682,7 +682,7 @@
BUG_ON(charge);
if (PageWriteback(page)) {
- if (!force)
+ if (!force || !sync)
goto uncharge;
wait_on_page_writeback(page);
}
@@ -827,7 +827,7 @@
*/
static int unmap_and_move_huge_page(new_page_t get_new_page,
unsigned long private, struct page *hpage,
- int force, int offlining)
+ int force, int offlining, bool sync)
{
int rc = 0;
int *result = NULL;
@@ -841,7 +841,7 @@
rc = -EAGAIN;
if (!trylock_page(hpage)) {
- if (!force)
+ if (!force || !sync)
goto out;
lock_page(hpage);
}
@@ -909,7 +909,8 @@
* Return: Number of pages not migrated or error code.
*/
int migrate_pages(struct list_head *from,
- new_page_t get_new_page, unsigned long private, int offlining)
+ new_page_t get_new_page, unsigned long private, int offlining,
+ bool sync)
{
int retry = 1;
int nr_failed = 0;
@@ -929,7 +930,8 @@
cond_resched();
rc = unmap_and_move(get_new_page, private,
- page, pass > 2, offlining);
+ page, pass > 2, offlining,
+ sync);
switch(rc) {
case -ENOMEM:
@@ -958,7 +960,8 @@
}
int migrate_huge_pages(struct list_head *from,
- new_page_t get_new_page, unsigned long private, int offlining)
+ new_page_t get_new_page, unsigned long private, int offlining,
+ bool sync)
{
int retry = 1;
int nr_failed = 0;
@@ -974,7 +977,8 @@
cond_resched();
rc = unmap_and_move_huge_page(get_new_page,
- private, page, pass > 2, offlining);
+ private, page, pass > 2, offlining,
+ sync);
switch(rc) {
case -ENOMEM:
@@ -1107,7 +1111,7 @@
err = 0;
if (!list_empty(&pagelist)) {
err = migrate_pages(&pagelist, new_page_node,
- (unsigned long)pm, 0);
+ (unsigned long)pm, 0, true);
if (err)
putback_lru_pages(&pagelist);
}