From 730cdc2c72c6905a2eda2fccbbf67dcef1206590 Mon Sep 17 00:00:00 2001 From: Chengming Zhou Date: Tue, 28 May 2024 13:15:21 +0800 Subject: [PATCH] mm/ksm: fix ksm_pages_scanned accounting Patch series "mm/ksm: fix some accounting problems", v3. We encountered some abnormal ksm_pages_scanned and ksm_zero_pages during some random tests. 1. ksm_pages_scanned unchanged even ksmd scanning has progress. 2. ksm_zero_pages maybe -1 in some rare cases. This patch (of 2): During testing, I found ksm_pages_scanned is unchanged although the scan_get_next_rmap_item() did return valid rmap_item that is not NULL. The reason is the scan_get_next_rmap_item() will return NULL after a full scan, so ksm_do_scan() just return without accounting of the ksm_pages_scanned. Fix it by just putting ksm_pages_scanned accounting in that loop, and it will be accounted more timely if that loop would last for a long time. Link: https://lkml.kernel.org/r/20240528-b4-ksm-counters-v3-0-34bb358fdc13@linux.dev Link: https://lkml.kernel.org/r/20240528-b4-ksm-counters-v3-1-34bb358fdc13@linux.dev Fixes: b348b5fe2b5f ("mm/ksm: add pages scanned metric") Signed-off-by: Chengming Zhou Acked-by: David Hildenbrand Reviewed-by: xu xin Cc: Andrea Arcangeli Cc: Hugh Dickins Cc: Ran Xiaokai Cc: Stefan Roesch Cc: Yang Yang Cc: Signed-off-by: Andrew Morton --- mm/ksm.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index 452ac8346e6e..9e99cb12d330 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2754,18 +2754,16 @@ static void ksm_do_scan(unsigned int scan_npages) { struct ksm_rmap_item *rmap_item; struct page *page; - unsigned int npages = scan_npages; - while (npages-- && likely(!freezing(current))) { + while (scan_npages-- && likely(!freezing(current))) { cond_resched(); rmap_item = scan_get_next_rmap_item(&page); if (!rmap_item) return; cmp_and_merge_page(page, rmap_item); put_page(page); + ksm_pages_scanned++; } - - ksm_pages_scanned += scan_npages - npages; } static int ksmd_should_run(void)