Messages in this thread |  | | Date | Thu, 05 Sep 2002 11:00:10 -0700 | From | Andrew Morton <> | Subject | Re: One more bio for for floppy users in 2.5.33.. |
| |
Linus Torvalds wrote: > > ... > A fast disk driver will _never ever_ do a partial request completion. A > high-performance subsystem will put in the scatter-gather list and say > "go" to the controller, and the controller will send exactly one interrupt > back when it is all done.
OK. But still, I don't see why we need partial BIO completions. If we say that the basic unit of completion is a whole BIO, then readahead can then manage latency via the outgoing bio size.
> So for such a system, you'd never see partial completions anyway. > > Partial completions are a feature of slow hardware. And slow hardware is > exactly when we want to know about it.
Well I'd be interested in knowing specifically what is wrong with the behaviour of 2.5.33 against a floppy disk.
In the testing I did a few weeks back, everything checked out. An application which was reading the raw device at 95% of media bandwidth never blocked. An application which was capable of processing data at 120% of media bandwidth achieved 100%.
It could be that the initial 64k read at the start-of-file is too big, and the many-small-file behaviour is poor?
A specific "this sucks" testcase would be helpful... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |