[1/3] mm, memory_hotplug: try to migrate full pfn range
diff mbox series

Message ID 20181211142741.2607-2-mhocko@kernel.org
State In Next
Commit f1b081c755d8f1b22ba1feff743cd96f9ceb622c
Headers show
Series
  • few memory offlining enhancements
Related show

Commit Message

Michal Hocko Dec. 11, 2018, 2:27 p.m. UTC
From: Michal Hocko <mhocko@suse.com>

do_migrate_range has been limiting the number of pages to migrate to 256
for some reason which is not documented. Even if the limit made some
sense back then when it was introduced it doesn't really serve a good
purpose these days. If the range contains huge pages then
we break out of the loop too early and go through LRU and pcp
caches draining and scan_movable_pages is quite suboptimal.

The only reason to limit the number of pages I can think of is to reduce
the potential time to react on the fatal signal. But even then the
number of pages is a questionable metric because even a single page
might migration block in a non-killable state (e.g. __unmap_and_move).

Remove the limit and offline the full requested range (this is one
membblock worth of pages with the current code). Should we ever get a
report that offlining takes too long to react on fatal signal then we
should rather fix the core migration to use killable waits and bailout
on a signal.

Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 mm/memory_hotplug.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

Comments

Wei Yang Dec. 12, 2018, 1:12 a.m. UTC | #1
On Tue, Dec 11, 2018 at 03:27:39PM +0100, Michal Hocko wrote:
>From: Michal Hocko <mhocko@suse.com>
>
>do_migrate_range has been limiting the number of pages to migrate to 256
>for some reason which is not documented. Even if the limit made some
>sense back then when it was introduced it doesn't really serve a good
>purpose these days. If the range contains huge pages then
>we break out of the loop too early and go through LRU and pcp
>caches draining and scan_movable_pages is quite suboptimal.
>
>The only reason to limit the number of pages I can think of is to reduce
>the potential time to react on the fatal signal. But even then the
>number of pages is a questionable metric because even a single page
>might migration block in a non-killable state (e.g. __unmap_and_move).
>
>Remove the limit and offline the full requested range (this is one
>membblock worth of pages with the current code). Should we ever get a

s/membblock/memblock/

Or memory block is more accurate? May memblock confuse audience with
lower level facility?

>report that offlining takes too long to react on fatal signal then we
>should rather fix the core migration to use killable waits and bailout
>on a signal.
>
>Reviewed-by: David Hildenbrand <david@redhat.com>
>Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
>Reviewed-by: Oscar Salvador <osalvador@suse.de>
>Signed-off-by: Michal Hocko <mhocko@suse.com>
>---
> mm/memory_hotplug.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
>diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>index c82193db4be6..6263c8cd4491 100644
>--- a/mm/memory_hotplug.c
>+++ b/mm/memory_hotplug.c
>@@ -1339,18 +1339,16 @@ static struct page *new_node_page(struct page *page, unsigned long private)
> 	return new_page_nodemask(page, nid, &nmask);
> }
> 
>-#define NR_OFFLINE_AT_ONCE_PAGES	(256)
> static int
> do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> {
> 	unsigned long pfn;
> 	struct page *page;
>-	int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
> 	int not_managed = 0;
> 	int ret = 0;
> 	LIST_HEAD(source);
> 
>-	for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
>+	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
> 		if (!pfn_valid(pfn))
> 			continue;
> 		page = pfn_to_page(pfn);
>@@ -1362,8 +1360,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> 				ret = -EBUSY;
> 				break;
> 			}
>-			if (isolate_huge_page(page, &source))
>-				move_pages -= 1 << compound_order(head);
>+			isolate_huge_page(page, &source);
> 			continue;
> 		} else if (PageTransHuge(page))
> 			pfn = page_to_pfn(compound_head(page))
>@@ -1382,7 +1379,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> 		if (!ret) { /* Success */
> 			put_page(page);
> 			list_add_tail(&page->lru, &source);
>-			move_pages--;
> 			if (!__PageMovable(page))
> 				inc_node_page_state(page, NR_ISOLATED_ANON +
> 						    page_is_file_cache(page));
>-- 
>2.19.2

Patch
diff mbox series

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c82193db4be6..6263c8cd4491 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1339,18 +1339,16 @@  static struct page *new_node_page(struct page *page, unsigned long private)
 	return new_page_nodemask(page, nid, &nmask);
 }
 
-#define NR_OFFLINE_AT_ONCE_PAGES	(256)
 static int
 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 {
 	unsigned long pfn;
 	struct page *page;
-	int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
 	int not_managed = 0;
 	int ret = 0;
 	LIST_HEAD(source);
 
-	for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
+	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
 		if (!pfn_valid(pfn))
 			continue;
 		page = pfn_to_page(pfn);
@@ -1362,8 +1360,7 @@  do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 				ret = -EBUSY;
 				break;
 			}
-			if (isolate_huge_page(page, &source))
-				move_pages -= 1 << compound_order(head);
+			isolate_huge_page(page, &source);
 			continue;
 		} else if (PageTransHuge(page))
 			pfn = page_to_pfn(compound_head(page))
@@ -1382,7 +1379,6 @@  do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 		if (!ret) { /* Success */
 			put_page(page);
 			list_add_tail(&page->lru, &source);
-			move_pages--;
 			if (!__PageMovable(page))
 				inc_node_page_state(page, NR_ISOLATED_ANON +
 						    page_is_file_cache(page));