Re: [PATCH V4 6/6] loop: add hint for handling aio via IOCB_NOWAIT

[Ming Lei <ming.lei@redhat.com>]

On Mon, Oct 13, 2025 at 2:28 PM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Thu, Oct 09, 2025 at 09:25:47AM +0800, Ming Lei wrote:
> > Firstly this FS flag isn't available, if it is added, we may take it into
> > account, and it is just one check, which shouldn't be blocker for this
> > loop perf improvement.
> >
> > Secondly it isn't enough to replace nowait decision from user side, one
> > case is overwrite, which is a nice usecase for nowait.
>
> Yes.  But right now you are hardcoding heuristics which is overall a
> very minor user of RWF_NOWAIT instead of sorting this out properly.

Yes, that is why I call the hint as loop specific, it isn't perfect, just for
avoiding potential regression by taking nowait.

Given the improvement is big, and the perf issue has been
reported several times, I'd suggest taking it this way first, and
document it can be improved in future.

Thanks,