Re: [PATCH v8 0/5] block: add larger order folio instead of pages

[Kundan Kumar <kundan.kumar@samsung.com>]

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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.


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