From: Filipe Manana fdmanana@suse.com
[ Upstream commit f2f121ab500d0457cc9c6f54269d21ffdf5bd304 ]
Every time we log an inode we lookup in the fs/subvol tree for xattrs and if we have any, log them into the log tree. However it is very common to have inodes without any xattrs, so doing the search wastes times, but more importantly it adds contention on the fs/subvol tree locks, either making the logging code block and wait for tree locks or making the logging code making other concurrent operations block and wait.
The most typical use cases where xattrs are used are when capabilities or ACLs are defined for an inode, or when SELinux is enabled.
This change makes the logging code detect when an inode does not have xattrs and skip the xattrs search the next time the inode is logged, unless the inode is evicted and loaded again or a xattr is added to the inode. Therefore skipping the search for xattrs on inodes that don't ever have xattrs and are fsynced with some frequency.
The following script that calls dbench was used to measure the impact of this change on a VM with 8 CPUs, 16Gb of ram, using a raw NVMe device directly (no intermediary filesystem on the host) and using a non-debug kernel (default configuration on Debian distributions):
$ cat test.sh #!/bin/bash
DEV=/dev/sdk MNT=/mnt/sdk MOUNT_OPTIONS="-o ssd"
mkfs.btrfs -f -m single -d single $DEV mount $MOUNT_OPTIONS $DEV $MNT
dbench -D $MNT -t 200 40
umount $MNT
The results before this change:
Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 5761605 0.172 312.057 Close 4232452 0.002 10.927 Rename 243937 1.406 277.344 Unlink 1163456 0.631 298.402 Deltree 160 11.581 221.107 Mkdir 80 0.003 0.005 Qpathinfo 5221410 0.065 122.309 Qfileinfo 915432 0.001 3.333 Qfsinfo 957555 0.003 3.992 Sfileinfo 469244 0.023 20.494 Find 2018865 0.448 123.659 WriteX 2874851 0.049 118.529 ReadX 9030579 0.004 21.654 LockX 18754 0.003 4.423 UnlockX 18754 0.002 0.331 Flush 403792 10.944 359.494
Throughput 908.444 MB/sec 40 clients 40 procs max_latency=359.500 ms
The results after this change:
Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 6442521 0.159 230.693 Close 4732357 0.002 10.972 Rename 272809 1.293 227.398 Unlink 1301059 0.563 218.500 Deltree 160 7.796 54.887 Mkdir 80 0.008 0.478 Qpathinfo 5839452 0.047 124.330 Qfileinfo 1023199 0.001 4.996 Qfsinfo 1070760 0.003 5.709 Sfileinfo 524790 0.033 21.765 Find 2257658 0.314 125.611 WriteX 3211520 0.040 232.135 ReadX 10098969 0.004 25.340 LockX 20974 0.003 1.569 UnlockX 20974 0.002 3.475 Flush 451553 10.287 331.037
Throughput 1011.77 MB/sec 40 clients 40 procs max_latency=331.045 ms
+10.8% throughput, -8.2% max latency
Reviewed-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Filipe Manana fdmanana@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/btrfs_inode.h | 7 +++++++ fs/btrfs/tree-log.c | 8 ++++++++ fs/btrfs/xattr.c | 4 +++- 3 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h index 92dd86bceae31..c974f7fe614ac 100644 --- a/fs/btrfs/btrfs_inode.h +++ b/fs/btrfs/btrfs_inode.h @@ -35,6 +35,13 @@ enum { BTRFS_INODE_IN_DELALLOC_LIST, BTRFS_INODE_HAS_PROPS, BTRFS_INODE_SNAPSHOT_FLUSH, + /* + * Set and used when logging an inode and it serves to signal that an + * inode does not have xattrs, so subsequent fsyncs can avoid searching + * for xattrs to log. This bit must be cleared whenever a xattr is added + * to an inode. + */ + BTRFS_INODE_NO_XATTRS, };
/* in memory btrfs inode */ diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 56cbc1706b6f7..5b11bb9770664 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -4571,6 +4571,10 @@ static int btrfs_log_all_xattrs(struct btrfs_trans_handle *trans, const u64 ino = btrfs_ino(inode); int ins_nr = 0; int start_slot = 0; + bool found_xattrs = false; + + if (test_bit(BTRFS_INODE_NO_XATTRS, &inode->runtime_flags)) + return 0;
key.objectid = ino; key.type = BTRFS_XATTR_ITEM_KEY; @@ -4609,6 +4613,7 @@ static int btrfs_log_all_xattrs(struct btrfs_trans_handle *trans, start_slot = slot; ins_nr++; path->slots[0]++; + found_xattrs = true; cond_resched(); } if (ins_nr > 0) { @@ -4618,6 +4623,9 @@ static int btrfs_log_all_xattrs(struct btrfs_trans_handle *trans, return ret; }
+ if (!found_xattrs) + set_bit(BTRFS_INODE_NO_XATTRS, &inode->runtime_flags); + return 0; }
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c index 95d9aebff2c4b..e51774201d53b 100644 --- a/fs/btrfs/xattr.c +++ b/fs/btrfs/xattr.c @@ -213,9 +213,11 @@ int btrfs_setxattr(struct btrfs_trans_handle *trans, struct inode *inode, } out: btrfs_free_path(path); - if (!ret) + if (!ret) { set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags); + clear_bit(BTRFS_INODE_NO_XATTRS, &BTRFS_I(inode)->runtime_flags); + } return ret; }