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Message-ID: <20250806161748.76651-3-ryncsn@gmail.com>
Date: Thu, 7 Aug 2025 00:17:47 +0800
From: Kairui Song <ryncsn@...il.com>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Kemeng Shi <shikemeng@...weicloud.com>,
Chris Li <chrisl@...nel.org>,
Nhat Pham <nphamcs@...il.com>,
Baoquan He <bhe@...hat.com>,
Barry Song <baohua@...nel.org>,
"Huang, Ying" <ying.huang@...ux.alibaba.com>,
linux-kernel@...r.kernel.org,
Kairui Song <kasong@...cent.com>
Subject: [PATCH v2 2/3] mm, swap: remove fragment clusters counter
From: Kairui Song <kasong@...cent.com>
It was used for calculating the iteration number when the swap allocator
wants to scan the whole fragment list. Now the allocator only scans one
fragment cluster at a time, so no one uses this counter anymore.
Remove it as a cleanup; the performance change is marginal:
Build linux kernel using 10G ZRAM, make -j96, defconfig with 2G cgroup
memory limit, on top of tmpfs, 64kB mTHP enabled:
Before: sys time: 6278.45s
After: sys time: 6176.34s
Change to 8G ZRAM:
Before: sys time: 5572.85s
After: sys time: 5531.49s
Signed-off-by: Kairui Song <kasong@...cent.com>
---
include/linux/swap.h | 1 -
mm/swapfile.c | 7 -------
2 files changed, 8 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 2fe6ed2cc3fd..a060d102e0d1 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -310,7 +310,6 @@ struct swap_info_struct {
/* list of cluster that contains at least one free slot */
struct list_head frag_clusters[SWAP_NR_ORDERS];
/* list of cluster that are fragmented or contented */
- atomic_long_t frag_cluster_nr[SWAP_NR_ORDERS];
unsigned int pages; /* total of usable pages of swap */
atomic_long_t inuse_pages; /* number of those currently in use */
struct swap_sequential_cluster *global_cluster; /* Use one global cluster for rotating device */
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 1f1110e37f68..5fdb3cb2b8b7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -470,11 +470,6 @@ static void move_cluster(struct swap_info_struct *si,
else
list_move_tail(&ci->list, list);
spin_unlock(&si->lock);
-
- if (ci->flags == CLUSTER_FLAG_FRAG)
- atomic_long_dec(&si->frag_cluster_nr[ci->order]);
- else if (new_flags == CLUSTER_FLAG_FRAG)
- atomic_long_inc(&si->frag_cluster_nr[ci->order]);
ci->flags = new_flags;
}
@@ -965,7 +960,6 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
* allocation, but reclaim may drop si->lock and race with another user.
*/
while ((ci = isolate_lock_cluster(si, &si->frag_clusters[o]))) {
- atomic_long_dec(&si->frag_cluster_nr[o]);
found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
0, usage);
if (found)
@@ -3217,7 +3211,6 @@ static struct swap_cluster_info *setup_clusters(struct swap_info_struct *si,
for (i = 0; i < SWAP_NR_ORDERS; i++) {
INIT_LIST_HEAD(&si->nonfull_clusters[i]);
INIT_LIST_HEAD(&si->frag_clusters[i]);
- atomic_long_set(&si->frag_cluster_nr[i], 0);
}
/*
--
2.50.1
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