Re: [RFC] FC pass thru - Rev V

FUJITA Tomonori
2009-02-11T17:21:19Z

On Wed, 11 Feb 2009 18:55:00 +0200
Boaz Harrosh <bharrosh@panasas.com> wrote:

> > It's about a bidi request. We already have tons of loops, memory
> > allocations, etc in the path. Do you think that adding one more loop
> > leads to a notable performance regression?
> >
> > Well, if you say that it's hacky then I would agree. But your patch
> > using ~0 is hacky too.
>
> It is an hack if used by an outside user, because it assumes knowledge
> of block-internals. It is much less of an hack if done by block-internals
> which knows for sure that this has no side effects.
>
> But I agree that this is not clean. The clean solution is to add an extra
> parameter to blk_end_request() and change all callers.

I don't agree.

> Or even cleaner is to add a new request->residual member and leave
> request->data_len be in peace. Then change the few users that care
> about residual, and one caller that sets it. I'll prepare a patch.

Yeah, it's clean but I'm not sure Jens would accept such patch since
fattening request struct leads to a notable performance regression.