Re: [PATCH v6 3/3] iomap: add simple dio path for small direct I/O

[Christoph Hellwig]

On Fri, Jul 03, 2026 at 05:13:12PM +0800, changfengnan wrote:
> taken, which introduced some overhead. 
> I implemented some optimizations based on Christoph’s suggestions and
> made some modifications to `iomap_process`; 
> Now, XFS performance is essentially unchanged, while ext4 still shows a
> 1.5% drop; I will continue to investigate the cause..   I’ve attached the patch.
> Actually, I had expected that switching to `iomap_next` would improve
> performance, since it avoids an indirect call.

I don't think it will for you - the direct I/O readers don't have
iomap_end methods, so you still have the same number of indirect
calls.  What could help is to inline the iterator as seen in Joannes'
fist demo series.  We could even look into doing that only for simple
dio in a first step, shifting the burden to use the simple method
to the callers (at least for the POC).