diff options
| author | Hugh Dickins <hughd@google.com> | 2022-02-14 18:29:54 -0800 |
|---|---|---|
| committer | Matthew Wilcox (Oracle) <willy@infradead.org> | 2022-02-17 11:56:57 -0500 |
| commit | 07ca760673088f262da57ff42c15558688565aa2 (patch) | |
| tree | 765db0e0ab2245a8e0cecc79ee97c47c294dac24 /mm/memcontrol.c | |
| parent | b109b87050df5438ee745b2bddfa3587970025bb (diff) | |
| download | linux-next-07ca760673088f262da57ff42c15558688565aa2.tar.gz | |
mm/munlock: maintain page->mlock_count while unevictable
Previous patches have been preparatory: now implement page->mlock_count.
The ordering of the "Unevictable LRU" is of no significance, and there is
no point holding unevictable pages on a list: place page->mlock_count to
overlay page->lru.prev (since page->lru.next is overlaid by compound_head,
which needs to be even so as not to satisfy PageTail - though 2 could be
added instead of 1 for each mlock, if that's ever an improvement).
But it's only safe to rely on or modify page->mlock_count while lruvec
lock is held and page is on unevictable "LRU" - we can save lots of edits
by continuing to pretend that there's an imaginary LRU here (there is an
unevictable count which still needs to be maintained, but not a list).
The mlock_count technique suffers from an unreliability much like with
page_mlock(): while someone else has the page off LRU, not much can
be done. As before, err on the safe side (behave as if mlock_count 0),
and let try_to_unlock_one() move the page to unevictable if reclaim finds
out later on - a few misplaced pages don't matter, what we want to avoid
is imbalancing reclaim by flooding evictable lists with unevictable pages.
I am not a fan of "if (!isolate_lru_page(page)) putback_lru_page(page);":
if we have taken lruvec lock to get the page off its present list, then
we save everyone trouble (and however many extra atomic ops) by putting
it on its destination list immediately.
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 36e9f38c919d..c78b9d3b9c04 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1257,8 +1257,7 @@ struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio, * @nr_pages: positive when adding or negative when removing * * This function must be called under lru_lock, just before a page is added - * to or just after a page is removed from an lru list (that ordering being - * so as to allow it to check that lru_size 0 is consistent with list_empty). + * to or just after a page is removed from an lru list. */ void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru, int zid, int nr_pages) |