On Thu, Aug 31, 2023 at 8:47 PM Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > On Thu, Aug 31, 2023 at 06:06:23PM -0700, Shawn wrote: > > Hi Dave, > > If ext size hint is not set at all, what's the default extent size > > alignment if the FS doesn't do striping (which is my case)? > > No alignment. XFS will allocate exact sized extents for the > writes being issued... => Seems this can explain why io_submit() latency was very high for small aio_write (4KB, 12KB, etc). When I did fallocate() 1MB space before moving on to the next 1MB chunk, then io_submit latency becomes normal. So ext size hint can achieve the same effect as fallocate() in this case, might be even better. > > -Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx
