Re: [PATCH] mkfs: use stx_blksize for dev block size by default

[Christoph Hellwig <hch@infradead.org>]

On Thu, Feb 06, 2025 at 07:00:55PM +0000, da.gomez@kernel.org wrote:
> From: Daniel Gomez <da.gomez@samsung.com>
> 
> In patch [1] ("bdev: use bdev_io_min() for statx block size"), block
> devices will now report their preferred minimum I/O size for optimal
> performance in the stx_blksize field of the statx data structure. This
> change updates the current default 4 KiB block size for all devices
> reporting a minimum I/O larger than 4 KiB, opting instead to query for
> its advertised minimum I/O value in the statx data struct.

UUuh, no.  Larger block sizes have their use cases, but this will
regress performance for a lot (most?) common setups.  A lot of
device report fairly high values there, but say increasing the
directory and bmap btree block size unconditionally using the current
algorithms will dramatically increase write amplification.  Similarly
for small buffered writes.