From b659ef027792219b590d67a2baf1643a93727d29 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Tue, 31 Mar 2015 14:16:52 +0100 Subject: [PATCH] Btrfs: avoid syncing log in the fast fsync path when not necessary Commit 3a8b36f37806 ("Btrfs: fix data loss in the fast fsync path") added a performance regression for that causes an unnecessary sync of the log trees (fs/subvol and root log trees) when 2 consecutive fsyncs are done against a file, without no writes or any metadata updates to the inode in between them and if a transaction is committed before the second fsync is called. Huang Ying reported this to lkml (https://lkml.org/lkml/2015/3/18/99) after a test sysbench test that measured a -62% decrease of file io requests per second for that tests' workload. The test is: echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor echo performance > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor echo performance > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor mkfs -t btrfs /dev/sda2 mount -t btrfs /dev/sda2 /fs/sda2 cd /fs/sda2 for ((i = 0; i < 1024; i++)); do fallocate -l 67108864 testfile.$i; done sysbench --test=fileio --max-requests=0 --num-threads=4 --max-time=600 \ --file-test-mode=rndwr --file-total-size=68719476736 --file-io-mode=sync \ --file-num=1024 run A test on kvm guest, running a debug kernel gave me the following results: Without 3a8b36f378060d: 16.01 reqs/sec With 3a8b36f378060d: 3.39 reqs/sec With 3a8b36f378060d and this patch: 16.04 reqs/sec Reported-by: Huang Ying Tested-by: Huang, Ying Signed-off-by: Filipe Manana Signed-off-by: Chris Mason --- fs/btrfs/file.c | 9 ++++++--- fs/btrfs/ordered-data.c | 14 ++++++++++++++ fs/btrfs/ordered-data.h | 3 +++ 3 files changed, 23 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index b072e17479aa..795d754327a7 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1868,6 +1868,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) struct btrfs_log_ctx ctx; int ret = 0; bool full_sync = 0; + const u64 len = end - start + 1; trace_btrfs_sync_file(file, datasync); @@ -1896,7 +1897,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) * all extents are persisted and the respective file extent * items are in the fs/subvol btree. */ - ret = btrfs_wait_ordered_range(inode, start, end - start + 1); + ret = btrfs_wait_ordered_range(inode, start, len); } else { /* * Start any new ordered operations before starting to log the @@ -1968,8 +1969,10 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) */ smp_mb(); if (btrfs_inode_in_log(inode, root->fs_info->generation) || - (full_sync && BTRFS_I(inode)->last_trans <= - root->fs_info->last_trans_committed)) { + (BTRFS_I(inode)->last_trans <= + root->fs_info->last_trans_committed && + (full_sync || + !btrfs_have_ordered_extents_in_range(inode, start, len)))) { /* * We'v had everything committed since the last time we were * modified so clear this flag in case it was set for whatever diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c index 47966cb3d4b6..ceccd078c93d 100644 --- a/fs/btrfs/ordered-data.c +++ b/fs/btrfs/ordered-data.c @@ -837,6 +837,20 @@ out: return entry; } +bool btrfs_have_ordered_extents_in_range(struct inode *inode, + u64 file_offset, + u64 len) +{ + struct btrfs_ordered_extent *oe; + + oe = btrfs_lookup_ordered_range(inode, file_offset, len); + if (oe) { + btrfs_put_ordered_extent(oe); + return true; + } + return false; +} + /* * lookup and return any extent before 'file_offset'. NULL is returned * if none is found diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h index a82cd7535d3c..7176cc0fe43f 100644 --- a/fs/btrfs/ordered-data.h +++ b/fs/btrfs/ordered-data.h @@ -188,6 +188,9 @@ btrfs_lookup_first_ordered_extent(struct inode * inode, u64 file_offset); struct btrfs_ordered_extent *btrfs_lookup_ordered_range(struct inode *inode, u64 file_offset, u64 len); +bool btrfs_have_ordered_extents_in_range(struct inode *inode, + u64 file_offset, + u64 len); int btrfs_ordered_update_i_size(struct inode *inode, u64 offset, struct btrfs_ordered_extent *ordered); int btrfs_find_ordered_sum(struct inode *inode, u64 offset, u64 disk_bytenr, -- 2.30.2