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Filipe Manana authored
When logging a regular file in full sync mode, we are currently committing its delayed inode item. This is to ensure that we never miss copying the inode item, with its most up to date data, into the log tree. However that is not necessary since commit e4545de5 ("Btrfs: fix fsync data loss after append write"), because even if we don't find the leaf with the inode item when looking for leaves that changed in the current transaction, we end up logging the inode item later using the in-memory content. In case we find the leaf containing the inode item, we already end up using the in-memory inode for filling the inode item in the log tree, and not the inode item that is in the fs/subvolume tree, as it might be not up to date (copy_items() -> fill_inode_item()). So don't commit the delayed inode item, which brings a couple of benefits: 1) Avoid writing the inode item to the fs/subvolume btree, saving time and reducing lock contention on the btree; 2) In case no other item for the inode was changed, added or deleted in the same leaf where the inode item is located, we ended up copying all the items in that leaf to the log tree - it's harmless from a functional point of view, but it wastes time and log tree space. This patch is part of a patch set comprised of the following patches: btrfs: check if a log tree exists at inode_logged() btrfs: remove no longer needed checks for NULL log context btrfs: do not log new dentries when logging that a new name exists btrfs: always update the logged transaction when logging new names btrfs: avoid expensive search when dropping inode items from log btrfs: add helper to truncate inode items when logging inode btrfs: avoid expensive search when truncating inode items from the log btrfs: avoid search for logged i_size when logging inode if possible btrfs: avoid attempt to drop extents when logging inode for the first time btrfs: do not commit delayed inode when logging a file in full sync mode This is patch 10/10 and the following test results compare a branch with the whole patch set applied versus a branch without any of the patches applied. The following script was used to test dbench with 8 and 16 jobs on a machine with 12 cores, 64G of RAM, a NVME device and using a non-debug kernel config (Debian's default): $ cat test.sh #!/bin/bash if [ $# -ne 1 ]; then echo "Use $0 NUM_JOBS" exit 1 fi NUM_JOBS=$1 DEV=/dev/nvme0n1 MNT=/mnt/nvme0n1 MOUNT_OPTIONS="-o ssd" MKFS_OPTIONS="-m single -d single" echo "performance" | \ tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor mkfs.btrfs -f $MKFS_OPTIONS $DEV mount $MOUNT_OPTIONS $DEV $MNT dbench -D $MNT -t 120 $NUM_JOBS umount $MNT The results were the following: 8 jobs, before patchset: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 4113896 0.009 238.665 Close 3021699 0.001 0.590 Rename 174215 0.082 238.733 Unlink 830977 0.049 238.642 Deltree 96 2.232 8.022 Mkdir 48 0.003 0.005 Qpathinfo 3729013 0.005 2.672 Qfileinfo 653206 0.001 0.152 Qfsinfo 683866 0.002 0.526 Sfileinfo 335055 0.004 1.571 Find 1441800 0.016 4.288 WriteX 2049644 0.010 3.982 ReadX 6449786 0.003 0.969 LockX 13400 0.002 0.043 UnlockX 13400 0.001 0.075 Flush 288349 2.521 245.516 Throughput 1075.73 MB/sec 8 clients 8 procs max_latency=245.520 ms 8 jobs, after patchset: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 4154282 0.009 156.675 Close 3051450 0.001 0.843 Rename 175912 0.072 4.444 Unlink 839067 0.048 66.050 Deltree 96 2.131 5.979 Mkdir 48 0.002 0.004 Qpathinfo 3765575 0.005 3.079 Qfileinfo 659582 0.001 0.099 Qfsinfo 690474 0.002 0.155 Sfileinfo 338366 0.004 1.419 Find 1455816 0.016 3.423 WriteX 2069538 0.010 4.328 ReadX 6512429 0.003 0.840 LockX 13530 0.002 0.078 UnlockX 13530 0.001 0.051 Flush 291158 2.500 163.468 Throughput 1105.45 MB/sec 8 clients 8 procs max_latency=163.474 ms +2.7% throughput, -40.1% max latency 16 jobs, before patchset: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 5457602 0.033 337.098 Close 4008979 0.002 2.018 Rename 231051 0.323 254.054 Unlink 1102209 0.202 337.243 Deltree 160 6.521 31.720 Mkdir 80 0.003 0.007 Qpathinfo 4946147 0.014 6.988 Qfileinfo 867440 0.001 1.642 Qfsinfo 907081 0.003 1.821 Sfileinfo 444433 0.005 2.053 Find 1912506 0.067 7.854 WriteX 2724852 0.018 7.428 ReadX 8553883 0.003 2.059 LockX 17770 0.003 0.350 UnlockX 17770 0.002 0.627 Flush 382533 2.810 353.691 Throughput 1413.09 MB/sec 16 clients 16 procs max_latency=353.696 ms 16 jobs, after patchset: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 5393156 0.034 303.181 Close 3961986 0.002 1.502 Rename 228359 0.320 253.379 Unlink 1088920 0.206 303.409 Deltree 160 6.419 30.088 Mkdir 80 0.003 0.004 Qpathinfo 48879676 0.015 7.722 Qfileinfo 857408 0.001 1.651 Qfsinfo 896343 0.002 2.147 Sfileinfo 439317 0.005 4.298 Find 1890018 0.073 8.347 WriteX 2693356 0.018 6.373 ReadX 8453485 0.003 3.836 LockX 17562 0.003 0.486 UnlockX 17562 0.002 0.635 Flush 378023 2.802 315.904 Throughput 1454.46 MB/sec 16 clients 16 procs max_latency=315.910 ms +2.9% throughput, -11.3% max latency Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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