[patch 053/262] mm: optimise put_pages_list()

Andrew Morton
2021-11-05T20:37:28Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: mm: optimise put_pages_list()

Instead of calling put_page() one page at a time, pop pages off the list
if their refcount was too high and pass the remainder to
put_unref_page_list(). This should be a speed improvement, but I have no
measurements to support that. Current callers do not care about
performance, but I hope to add some which do.

Link: https://lkml.kernel.org/r/20211007192138.561673-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/swap.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)

--- a/mm/swap.c~mm-optimise-put_pages_list
+++ a/mm/swap.c
@@ -134,18 +134,27 @@ EXPORT_SYMBOL(__put_page);
* put_pages_list() - release a list of pages
* @pages: list of pages threaded on page->lru
*
- * Release a list of pages which are strung together on page.lru. Currently
- * used by read_cache_pages() and related error recovery code.
+ * Release a list of pages which are strung together on page.lru.
*/
void put_pages_list(struct list_head *pages)
{
- while (!list_empty(pages)) {
- struct page *victim;
+ struct page *page, *next;

- victim = lru_to_page(pages);
- list_del(&victim->lru);
- put_page(victim);
+ list_for_each_entry_safe(page, next, pages, lru) {
+ if (!put_page_testzero(page)) {
+ list_del(&page->lru);
+ continue;
+ }
+ if (PageHead(page)) {
+ list_del(&page->lru);
+ __put_compound_page(page);
+ continue;
+ }
+ /* Cannot be PageLRU because it's passed to us using the lru */
+ __ClearPageWaiters(page);
}
+
+ free_unref_page_list(pages);
}
EXPORT_SYMBOL(put_pages_list);

_