Re: [f2fs-dev] [PATCH v2] f2fs: another way to set large folio by remembering inode number

[Christoph Hellwig]

On Tue, May 26, 2026 at 09:14:52AM -0700, Bart Van Assche wrote:
> On 5/26/26 6:42 AM, Theodore Tso wrote:
> > It seems... surprising that the additional I/O operations are actually
> > throttloing UFS device bandwidth by 2x (4GB/s vs 2GB/s).  Have you dug
> > into why this is happening, and whether there is anything that can be
> > optimized below the file system?
> The layers below the filesystem (block, SCSI, UFS) is what I'm
> responsible for in the Pixel team and I can assure you that these are
> highly optimized.
> 
> Since the transfer size used in Jaegeuk's tests is much larger than 4
> KiB, how many CPU cycles are used per IO by the layers below the
> filesystem is not limiting the transfer bandwidth.

I'm honestly not sure what discussion we have here.  Larger I/O is
pretty much always more efficient.  If you submit smaller I/O you
need more merging to build it back up larger, and more I/Os.

Which is exaxtly why we need large folio support everywhere, as it
makes a huge difference in I/O performance.