From e26daa536abf37ef17302f42443919a98a7d5522 Mon Sep 17 00:00:00 2001 From: Kairui Song Date: Tue, 25 Feb 2025 02:02:09 +0800 Subject: [PATCH] mm, swap: don't update the counter up-front The counter update before allocation design was useful to avoid unnecessary scan when device is full, so it will abort early if the counter indicates the device is full. But that is an uncommon case, and now scanning of a full device is very fast, so the up-front update is not helpful any more. Remove it and simplify the slot allocation logic. Link: https://lkml.kernel.org/r/20250224180212.22802-5-ryncsn@gmail.com Signed-off-by: Kairui Song Reviewed-by: Baoquan He Cc: Baolin Wang Cc: Barry Song Cc: Chris Li Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kalesh Singh Cc: Matthew Wilcow (Oracle) Cc: Nhat Pham Cc: Yosry Ahmed Signed-off-by: Andrew Morton --- mm/swapfile.c | 18 ++---------------- 1 file changed, 2 insertions(+), 16 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 6f2de59c6355..db836670c334 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1201,22 +1201,10 @@ int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_order) int order = swap_entry_order(entry_order); unsigned long size = 1 << order; struct swap_info_struct *si, *next; - long avail_pgs; int n_ret = 0; int node; spin_lock(&swap_avail_lock); - - avail_pgs = atomic_long_read(&nr_swap_pages) / size; - if (avail_pgs <= 0) { - spin_unlock(&swap_avail_lock); - goto noswap; - } - - n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs); - - atomic_long_sub(n_goal * size, &nr_swap_pages); - start_over: node = numa_node_id(); plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) { @@ -1250,10 +1238,8 @@ start_over: spin_unlock(&swap_avail_lock); check_out: - if (n_ret < n_goal) - atomic_long_add((long)(n_goal - n_ret) * size, - &nr_swap_pages); -noswap: + atomic_long_sub(n_ret * size, &nr_swap_pages); + return n_ret; } -- 2.49.0