The patch titled
Subject: mm, swap: don't update the counter up-front
has been added to the -mm mm-unstable branch. Its filename is
mm-swap-dont-update-the-counter-up-front.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swap-dont-update-the-counter-up-front.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Kairui Song <kasong@xxxxxxxxxxx>
Subject: mm, swap: don't update the counter up-front
Date: Tue, 25 Feb 2025 02:02:09 +0800
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@xxxxxxxxx
Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Barry Song <v-songbaohua@xxxxxxxx>
Cc: Chris Li <chrisl@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Matthew Wilcow (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 18 ++----------------
1 file changed, 2 insertions(+), 16 deletions(-)
--- a/mm/swapfile.c~mm-swap-dont-update-the-counter-up-front
+++ a/mm/swapfile.c
@@ -1201,22 +1201,10 @@ int get_swap_pages(int n_goal, swp_entry
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;
}
_
Patches currently in -mm which might be from kasong@xxxxxxxxxxx are
mm-swap-avoid-reclaiming-irrelevant-swap-cache.patch
mm-swap-drop-the-flag-ttrs_direct.patch
mm-swap-avoid-redundant-swap-device-pinning.patch
mm-swap-dont-update-the-counter-up-front.patch
mm-swap-use-percpu-cluster-as-allocation-fast-path.patch
mm-swap-remove-swap-slot-cache.patch
mm-swap-simplify-folio-swap-allocation.patch
