Hi, At 2024-09-09 21:37:35, "Kent Overstreet" <[email protected]> wrote: >On Sat, Sep 07, 2024 at 06:34:37PM GMT, David Wang wrote:
> >Big standard deviation (high tail latency?) is something we'd want to >track down. There's a bunch of time_stats in sysfs, but they're mostly >for the write paths. If you're trying to identify where the latencies >are coming from, we can look at adding some new time stats to isolate. About performance, I have a theory based on some observation I made recently: When user space app make a 4k(8 sectors) direct write, bcachefs would initiate a write request of ~11 sectors, including the checksum data, right? This may not be a good offset+size pattern of block layer for performance. (I did get a very-very bad performance on ext4 if write with 5K size.) So I think, would it be feasible to make checksum sectors on a 4/8 sector boundary? This will waste more diskspace, but may make block layer happy? Thanks David
