On Mon, Mar 03, 2014 at 11:53:28PM +0100, Jan Kara wrote:
> When doing filesystem wide sync, there's no need to force transaction
> commit (or synchronously write inode buffer) separately for each inode
> because ext4_sync_fs() takes care of forcing commit at the end (VFS
> takes care of flushing buffer cache, respectively). Most of the time
> this slowness doesn't manifest because previous WB_SYNC_NONE writeback
> doesn't leave much to write but when there are processes aggressively
> creating new files and several filesystems to sync, the sync slowness
> can be noticeable. In the following test script sync(1) takes around 6
> minutes when there are two ext4 filesystems mounted on a standard SATA
> drive. After this patch sync takes a couple of seconds so we have about
> two orders of magnitude improvement.
>
> function run_writers
> {
> for (( i = 0; i < 10; i++ )); do
> mkdir $1/dir$i
> for (( j = 0; j < 40000; j++ )); do
> dd if=/dev/zero of=$1/dir$i/$j bs=4k count=4 &>/dev/null
> done &
> done
> }
>
> for dir in "$@"; do
> run_writers $dir
> done
>
> sleep 40
> time sync
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
Looks good, thanks for the patch!
- Ted
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