Re: RFC on io-stalls patch

Jens Axboe (
Mon, 14 Jul 2003 07:49:18 +0200

On Sun, Jul 13 2003, Andrea Arcangeli wrote:
> On Sun, Jul 13, 2003 at 11:01:16AM +0200, Jens Axboe wrote:
> > No I don't have anything specific, it just seems like a bad heuristic to
> > get rid of. I can try and do some testing tomorrow. I do feel strongly
> well, it's not an heuristic, it's a simplification and it will certainly
> won't provide any benefit (besides saving some hundred kbytes of ram per
> harddisk that is a minor benefit).

You are missing my point - I don't care about loosing the extra request
list, I never said anything about that in this thread. I care about
loosing the reserved requests for reads. And we can do that just fine
with just holding back a handful of requests.

> > that we should at least make sure to reserve a few requests for reads
> > exclusively, even if you don't agree with the oversized check. Anything
> > else really contradicts all the io testing we have done the past years
> > that shows how important it is to get a read in ASAP. And doing that in
> Important for latency or throughput? Do you know which is the benchmarks
> that returned better results with the two queues, what's the theory
> behind this?

Forget the two queues, noone has said anything about that. The reserved
reads are important for latency reasons, not throughput.

Jens Axboe

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