On 12/08/24 09:35AM, Luis Chamberlain wrote:
On Mon, Aug 12, 2024 at 03:38:43PM +0200, Christoph Hellwig wrote:
On Thu, Aug 08, 2024 at 04:04:03PM -0700, Luis Chamberlain wrote:
> This is not just about mTHP uses though, this can also affect buffered IO and
> direct IO patterns as well and this needs to be considered and tested as well.
Not sure what the above is supposed to mean. Besides small tweaks
to very low-level helpers the changes are entirely in the direct I/O
path, and they optimize that path for folios larger than PAGE_SIZE.
Which was my expectation as well.
> I've given this a spin on top of of the LBS patches [0] and used the LBS
> patches as a baseline. The good news is I see a considerable amount of
> larger IOs for buffered IO and direct IO, however for buffered IO there
> is an increase on unalignenment to the target filesystem block size and
> that can affect performance.
Compared to what? There is nothing in the series here changing buffered
I/O patterns. What do you compare? If this series changes buffered
I/O patterns that is very well hidden and accidental, so we need to
bisect which patch does it and figure out why, but it would surprise me
a lot.
The comparison was the without the patches Vs with the patches on the
same fio run with buffered IO. I'll re-test more times and bisect.
Did tests with LBS + block folio patches and couldn't observe alignment
issue. Also, the changes in this series are not executed when we issue
buffered I/O.
