Re: [patch] use cheaper elv_queue_empty when unplug a device

Jens Axboe
2005-03-29T10:20:48Z

On Tue, Mar 29 2005, Arjan van de Ven wrote:
> On Tue, 2005-03-29 at 19:19 +1000, Nick Piggin wrote:
> > - removes the relock/retry merge mechanism in __make_request if we
> > aren't able to get the GFP_ATOMIC allocation. Just fall through
> > and assume the chances of getting a merge will be small (is this
> > a valid assumption? Should measure it I guess).
>
> this may have a potential problem; if the vm gets in trouble, you
> suddenly start to generate worse IO patterns, which means IO performance
> goes down right when it's most needed.....
>
> of course we need to figure if this actually ever hits in practice,
> because if it doesn't I'm all for simpler code.

Precisely, see my response as well. If the noretry flag works, that
should be fine.

--
Jens Axboe