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dc51616486
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David Sterba dc51616486 btrfs: reorder extent buffer members for better packing 
After the rwsem replaced the tree lock implementation, the extent buffer
got smaller but leaving some holes behind. By changing log_index type
and reordering, we can squeeze the size further to 240 bytes, measured on
release config on x86_64. Log_index spans only 3 values and needs to be
signed.

Before:

struct extent_buffer {
        u64                        start;                /*     0     8 */
        long unsigned int          len;                  /*     8     8 */
        long unsigned int          bflags;               /*    16     8 */
        struct btrfs_fs_info *     fs_info;              /*    24     8 */
        spinlock_t                 refs_lock;            /*    32     4 */
        atomic_t                   refs;                 /*    36     4 */
        atomic_t                   io_pages;             /*    40     4 */
        int                        read_mirror;          /*    44     4 */
        struct callback_head       callback_head __attribute__((__aligned__(8))); /*    48    16 */
        /* --- cacheline 1 boundary (64 bytes) --- */
        pid_t                      lock_owner;           /*    64     4 */
        bool                       lock_recursed;        /*    68     1 */

        /* XXX 3 bytes hole, try to pack */

        struct rw_semaphore        lock;                 /*    72    40 */
        short int                  log_index;            /*   112     2 */

        /* XXX 6 bytes hole, try to pack */

        struct page *              pages[16];            /*   120   128 */

        /* size: 248, cachelines: 4, members: 14 */
        /* sum members: 239, holes: 2, sum holes: 9 */
        /* forced alignments: 1 */
        /* last cacheline: 56 bytes */
} __attribute__((__aligned__(8)));

After:

struct extent_buffer {
        u64                        start;                /*     0     8 */
        long unsigned int          len;                  /*     8     8 */
        long unsigned int          bflags;               /*    16     8 */
        struct btrfs_fs_info *     fs_info;              /*    24     8 */
        spinlock_t                 refs_lock;            /*    32     4 */
        atomic_t                   refs;                 /*    36     4 */
        atomic_t                   io_pages;             /*    40     4 */
        int                        read_mirror;          /*    44     4 */
        struct callback_head       callback_head __attribute__((__aligned__(8))); /*    48    16 */
        /* --- cacheline 1 boundary (64 bytes) --- */
        pid_t                      lock_owner;           /*    64     4 */
        bool                       lock_recursed;        /*    68     1 */
        s8                         log_index;            /*    69     1 */

        /* XXX 2 bytes hole, try to pack */

        struct rw_semaphore        lock;                 /*    72    40 */
        struct page *              pages[16];            /*   112   128 */

        /* size: 240, cachelines: 4, members: 14 */
        /* sum members: 238, holes: 1, sum holes: 2 */
        /* forced alignments: 1 */
        /* last cacheline: 48 bytes */
} __attribute__((__aligned__(8)));

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:02 +01:00
..
tests btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
acl.c
async-thread.c Btrfs: fix crash during unmount due to race with delayed inode workers 2020-03-23 17:01:51 +01:00
async-thread.h Btrfs: fix crash during unmount due to race with delayed inode workers 2020-03-23 17:01:51 +01:00
backref.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
backref.h btrfs: rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE 2020-05-25 11:25:35 +02:00
block-group.c btrfs: introduce mount option rescue=ignorebadroots 2020-12-08 15:53:41 +01:00
block-group.h btrfs: convert block group refcount to refcount_t 2020-07-27 12:55:42 +02:00
block-rsv.c btrfs: introduce mount option rescue=ignorebadroots 2020-12-08 15:53:41 +01:00
block-rsv.h btrfs: Remove __ prefix from btrfs_block_rsv_release 2020-03-23 17:01:55 +01:00
btrfs_inode.h btrfs: switch cached fs_info::csum_size from u16 to u32 2020-12-08 15:53:59 +01:00
check-integrity.c btrfs: check integrity: remove local copy of csum_size 2020-12-08 15:54:01 +01:00
check-integrity.h btrfs: remove btrfsic_submit_bh() 2020-03-23 17:01:39 +01:00
compression.c btrfs: remove unnecessary local variables for checksum size 2020-12-08 15:54:00 +01:00
compression.h btrfs: compression: move declarations to header 2020-10-07 12:06:55 +02:00
ctree.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
ctree.h btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
delalloc-space.c btrfs: add btrfs_reserve_data_bytes and use it 2020-10-07 12:06:52 +02:00
delalloc-space.h btrfs: make btrfs_delalloc_reserve_space take btrfs_inode 2020-07-27 12:55:36 +02:00
delayed-inode.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
delayed-inode.h btrfs: delayed-inode: Replace zero-length array with flexible-array member 2020-03-23 17:01:53 +01:00
delayed-ref.c btrfs: Remove __ prefix from btrfs_block_rsv_release 2020-03-23 17:01:55 +01:00
delayed-ref.h
dev-replace.c btrfs: dev-replace: fail mount if we don't have replace item with target device 2020-11-05 13:03:31 +01:00
dev-replace.h
dir-item.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
discard.c btrfs: discard: add missing put when grabbing block group from unused list 2020-07-07 16:06:28 +02:00
discard.h btrfs: discard: Use the correct style for SPDX License Identifier 2020-04-20 17:43:42 +02:00
disk-io.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
disk-io.h btrfs: replace fs_info and private_data with inode in btrfs_wq_submit_bio 2020-12-08 15:53:54 +01:00
export.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
export.h btrfs: export helpers for subvolume name/id resolution 2020-03-23 17:01:42 +01:00
extent_io.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
extent_io.h btrfs: reorder extent buffer members for better packing 2020-12-08 15:54:02 +01:00
extent_map.c Btrfs: fix race between using extent maps and merging them 2020-02-12 17:16:46 +01:00
extent_map.h btrfs: remove extent_map::bdev 2019-11-18 23:43:44 +01:00
extent-io-tree.h btrfs: sink the failed_start parameter to set_extent_bit 2020-12-08 15:53:54 +01:00
extent-tree.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
file-item.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
file.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
free-space-cache.c btrfs: set EXTENT_NORESERVE bits side btrfs_dirty_pages() 2020-12-08 15:53:38 +01:00
free-space-cache.h btrfs: let btrfs_return_cluster_to_free_space() return void 2020-07-27 12:55:21 +02:00
free-space-tree.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
free-space-tree.h btrfs: rename btrfs_block_group_cache 2019-11-18 17:51:51 +01:00
inode-item.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
inode-map.c btrfs: make btrfs_delalloc_reserve_space take btrfs_inode 2020-07-27 12:55:36 +02:00
inode-map.h
inode.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
ioctl.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
Kconfig btrfs: switch to iomap for direct IO 2020-10-07 12:06:57 +02:00
locking.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
locking.h btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
lzo.c
Makefile Btrfs: move all reflink implementation code into its own file 2020-03-23 17:01:54 +01:00
misc.h btrfs: rename tree_entry to rb_simple_node and export it 2020-05-25 11:25:19 +02:00
ordered-data.c btrfs: switch cached fs_info::csum_size from u16 to u32 2020-12-08 15:53:59 +01:00
ordered-data.h btrfs: remove unnecessary local variables for checksum size 2020-12-08 15:54:00 +01:00
orphan.c
print-tree.c btrfs: remove unnecessary casts in printk 2020-12-08 15:53:52 +01:00
print-tree.h btrfs: pretty print leaked root name 2020-10-07 12:12:20 +02:00
props.c btrfs: simplify iget helpers 2020-05-25 11:25:37 +02:00
props.h
qgroup.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
qgroup.h btrfs: qgroup: export qgroups in sysfs 2020-07-27 12:55:37 +02:00
raid56.c btrfs: raid56: remove out label in __raid56_parity_recover 2020-07-27 12:55:44 +02:00
raid56.h
rcu-string.h btrfs: rcu-string: Replace zero-length array with flexible-array member 2020-03-23 17:01:53 +01:00
reada.c btrfs: assert we are holding the reada_lock when releasing a readahead zone 2020-12-08 15:53:38 +01:00
ref-verify.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
ref-verify.h
reflink.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
reflink.h Btrfs: move all reflink implementation code into its own file 2020-03-23 17:01:54 +01:00
relocation.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
root-tree.c btrfs: qgroup: fix qgroup meta rsv leak for subvolume operations 2020-10-07 12:12:13 +02:00
scrub.c btrfs: scrub: remove local copy of csum_size from context 2020-12-08 15:54:01 +01:00
send.c btrfs: send: use helpers to access root_item::ctransid 2020-12-08 15:53:51 +01:00
send.h btrfs: send: avoid copying file data 2020-10-07 12:13:17 +02:00
space-info.c btrfs: kill the RCU protection for fs_info->space_info 2020-10-07 12:13:19 +02:00
space-info.h btrfs: add btrfs_reserve_data_bytes and use it 2020-10-07 12:06:52 +02:00
struct-funcs.c btrfs: use unaligned helpers for stack and header set/get helpers 2020-10-07 12:13:23 +02:00
super.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
sysfs.c btrfs: sysfs: add per-fs attribute for read policy 2020-12-08 15:53:45 +01:00
sysfs.h btrfs: split and refactor btrfs_sysfs_remove_devices_dir 2020-10-07 12:12:21 +02:00
transaction.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
transaction.h btrfs: remove dio iomap DSYNC workaround 2020-12-08 15:53:49 +01:00
tree-checker.c btrfs: switch cached fs_info::csum_size from u16 to u32 2020-12-08 15:53:59 +01:00
tree-checker.h
tree-defrag.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
tree-log.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
tree-log.h btrfs: make fast fsyncs wait only for writeback 2020-10-07 12:06:56 +02:00
ulist.c
ulist.h
uuid-tree.c btrfs: remove unnecessary casts in printk 2020-12-08 15:53:52 +01:00
volumes.c btrfs: create read policy framework 2020-12-08 15:53:44 +01:00
volumes.h btrfs: create read policy framework 2020-12-08 15:53:44 +01:00
xattr.c
xattr.h
zlib.c btrfs: use larger zlib buffer for s390 hardware compression 2020-01-31 10:30:40 -08:00
zstd.c