From 0bba9af03d55d2cc1aa7616a8b9e522ceb49d180 Mon Sep 17 00:00:00 2001 From: Zhenhua Huang Date: Wed, 7 Sep 2022 16:01:13 +0800 Subject: mm/page_owner.c: remove redundant drain_all_pages Remove an expensive and unnecessary operation as PCP pages are safely skipped when reading page owner.PCP pages can be skipped because PAGE_EXT_OWNER_ALLOCATED is cleared. With draining PCP pages, these pages are moved to buddy list so they can be identified as buddy pages and skipped quickly. Although it improved efficiency of PFN walker, the drain is guaranteed expensive that is unlikely to be offset by a slight increase in efficiency when skipping free pages. PAGE_EXT_OWNER_ALLOCATED is cleared in the page owner reset path below: free_unref_page -> free_unref_page_prepare -> free_pcp_prepare -> free_pages_prepare which do page owner reset -> free_unref_page_commit which add pages into pcp list Link: https://lkml.kernel.org/r/1662704326-15899-1-git-send-email-quic_zhenhuah@quicinc.com Link: https://lkml.kernel.org/r/1662633204-10044-1-git-send-email-quic_zhenhuah@quicinc.com Link: https://lkml.kernel.org/r/1662537673-9392-1-git-send-email-quic_zhenhuah@quicinc.com Signed-off-by: Zhenhua Huang Acked-by: Mel Gorman Signed-off-by: Andrew Morton --- mm/page_owner.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'mm/page_owner.c') diff --git a/mm/page_owner.c b/mm/page_owner.c index 90023f938c19..54f3e039fb48 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -524,8 +524,6 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0) pfn++; - drain_all_pages(NULL); - /* Find an allocated page */ for (; pfn < max_pfn; pfn++) { /* -- cgit v1.2.3