[lkml]   [2002]   [Sep]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: 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
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:28    [W:0.080 / U:4.812 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site