On 03/30/2016 09:12 AM, Minchan Kim wrote:
Now, VM has a feature to migrate non-lru movable pages so
balloon doesn't need custom migration hooks in migrate.c
and compact.c. Instead, this patch implements page->mapping
->{isolate|migrate|putback} functions.
With that, we could remove hooks for ballooning in general
migration functions and make balloon compaction simple.
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Rafael Aquini <aquini@xxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Signed-off-by: Gioh Kim <gurugio@xxxxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
I'm not familiar with the inode and pseudofs stuff, so just some things
I noticed:
-#define PAGE_MOVABLE_MAPCOUNT_VALUE (-255)
+#define PAGE_MOVABLE_MAPCOUNT_VALUE (-256)
+#define PAGE_BALLOON_MAPCOUNT_VALUE PAGE_MOVABLE_MAPCOUNT_VALUE
static inline int PageMovable(struct page *page)
{
- return ((test_bit(PG_movable, &(page)->flags) &&
- atomic_read(&page->_mapcount) == PAGE_MOVABLE_MAPCOUNT_VALUE)
- || PageBalloon(page));
+ return (test_bit(PG_movable, &(page)->flags) &&
+ atomic_read(&page->_mapcount) == PAGE_MOVABLE_MAPCOUNT_VALUE);
}
/* Caller should hold a PG_lock */
@@ -645,6 +626,35 @@ static inline void __ClearPageMovable(struct page *page)
PAGEFLAG(Isolated, isolated, PF_ANY);
+static inline int PageBalloon(struct page *page)
+{
+ return atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE
+ && PagePrivate2(page);
+}
Hmm so you are now using PG_private_2 flag here, but it's not
documented. Also the only caller of PageBalloon() seems to be
stable_page_flags(). Which will now report all movable pages with
PG_private_2 as KPF_BALOON. Seems like an overkill and also not
reliable. Could it test e.g. page->mapping instead?
Or maybe if we manage to get rid of PAGE_MOVABLE_MAPCOUNT_VALUE, we can
keep PAGE_BALLOON_MAPCOUNT_VALUE to simply distinguish balloon pages for
stable_page_flags().
@@ -1033,7 +1019,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
out:
/* If migration is successful, move newpage to right list */
if (rc == MIGRATEPAGE_SUCCESS) {
- if (unlikely(__is_movable_balloon_page(newpage)))
+ if (unlikely(PageMovable(newpage)))
put_page(newpage);
else
putback_lru_page(newpage);
Hmm shouldn't the condition have been changed to
if (unlikely(__is_movable_balloon_page(newpage)) || PageMovable(newpage)
by patch 02/16? And this patch should be just removing the
balloon-specific check? Otherwise it seems like between patches 02 and
04, other kinds of PageMovable pages were unnecessarily/wrongly routed
through putback_lru_page()?
diff --git a/mm/vmscan.c b/mm/vmscan.c
index d82196244340..c7696a2e11c7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1254,7 +1254,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
list_for_each_entry_safe(page, next, page_list, lru) {
if (page_is_file_cache(page) && !PageDirty(page) &&
- !isolated_balloon_page(page)) {
+ !PageIsolated(page)) {
ClearPageActive(page);
list_move(&page->lru, &clean_pages);
}
This looks like the same comment as above at first glance. But looking
closer, it's even weirder. isolated_balloon_page() was simply
PageBalloon() after d6d86c0a7f8dd... weird already. You replace it with
check for !PageIsolated() which looks like a more correct check, so ok.
Except the potential false positive with PG_owner_priv_1.
Thanks.
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