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btrfs: reorder members in btrfs_delayed_root for better packing

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There are two unnecessary 4B holes in btrfs_delayed_root;

struct btrfs_delayed_root {
        spinlock_t                 lock;                 /*     0     4 */

        /* XXX 4 bytes hole, try to pack */

        struct list_head           node_list;            /*     8    16 */
        struct list_head           prepare_list;         /*    24    16 */
        atomic_t                   items;                /*    40     4 */
        atomic_t                   items_seq;            /*    44     4 */
        int                        nodes;                /*    48     4 */

        /* XXX 4 bytes hole, try to pack */

        wait_queue_head_t          wait;                 /*    56    24 */

        /* size: 80, cachelines: 2, members: 7 */
        /* sum members: 72, holes: 2, sum holes: 8 */
        /* last cacheline: 16 bytes */
};

Reordering 'nodes' after 'lock' reduces size by 8B, to 72 on release
config.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2026-01-09 18:17:41 +01:00
parent c8bafc8d6a
commit 86523d8d2f
1 changed files with 1 additions and 1 deletions
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2
fs/btrfs/fs.h
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@ -465,6 +465,7 @@ struct btrfs_commit_stats {
struct btrfs_delayed_root {
spinlock_t lock;
int nodes; /* for delayed nodes */
struct list_head node_list;
/*
* Used for delayed nodes which is waiting to be dealt with by the
@ -474,7 +475,6 @@ struct btrfs_delayed_root {
struct list_head prepare_list;
atomic_t items; /* for delayed items */
atomic_t items_seq; /* for delayed items */
int nodes; /* for delayed nodes */
wait_queue_head_t wait;
};