On Wed, Oct 16, 2013 at 09:18:37AM +0800, Ming Lei wrote: > Commit 4e7ea81db5(ext4: restructure writeback path) introduces > another performance regression on random write: > > - one more page may be added to ext4 extent in mpage_prepare_extent_to_map, > and will be submitted for I/O so nr_to_write will become -1 before 'done' > is set > > - the worse thing is that dirty pages may still be retrieved from page > cache after nr_to_write becomes negative, so lots of small chunks can be > submitted to block device when page writeback is catching up with write > path, and performance is hurted. > > On one arm A15 board with sata 3.0 SSD(CPU: 1.5GHz dura core, RAM: 2GB, > SATA controller: 3.0Gbps), this patch can improve below test's result > from 157MB/sec to 174MB/sec(>10%): > > dd if=/dev/zero of=./z.img bs=8K count=512K > > The above test is actually prototype of block write in bonnie++ utility. > > This patch makes sure no more pages than nr_to_write can be added to extent > for mapping, so that nr_to_write won't become negative. > > Cc: Ted Tso <tytso@xxxxxxx> > Cc: linux-ext4@xxxxxxxxxxxxxxx > Cc: "linux-fsdevel@xxxxxxxxxxxxxxx" <linux-fsdevel@xxxxxxxxxxxxxxx> > Acked-by: Jan Kara <jack@xxxxxxx> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> Thanks, applied. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
