On Thu, Jun 13, 2019 at 05:33:46PM -0700, Tejun Heo wrote: > From: Chris Mason <clm@xxxxxx> > > btrfs_schedule_bio() hands IO off to a helper thread to do the actual > submit_bio() call. This has been used to make sure async crc and > compression helpers don't get stuck on IO submission. To maintain good > performance, over time the IO submission threads duplicated some IO > scheduler characteristics such as high and low priority IOs and they > also made some ugly assumptions about request allocation batch sizes. > > All of this cost at least one extra context switch during IO submission, > and doesn't fit well with the modern blkmq IO stack. So, this commit stops > using btrfs_schedule_bio(). We may need to adjust the number of async > helper threads for crcs and compression, but long term it's a better > path. > > Signed-off-by: Chris Mason <clm@xxxxxx> Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Thanks, Josef
