Re: [patch] vmfixes-2.4.0-test9-B2

Ingo Molnar
2000-09-25T13:10:51Z

On Mon, 25 Sep 2000, Andrea Arcangeli wrote:

> > yet another elevator algorithm we need a squeaky clean VM balancer above
>
> FYI: My current tree (based on 2.4.0-test8-pre5) delivers 16mbyte/sec
> in the tiobench write test compared to clean 2.4.0-test8-pre5 that
> delivers 8mbyte/sec

great! I'm happy we have a fine-tuned elevator again.

> Also I I found the reason of your hang, it's the TASK_EXCLUSIVE in
> wait_for_request. The high part of the queue is reserved for reads.
> Now if a read completes and it wakeups a write you'll hang.

yep. But i dont understand why this makes any difference - the waitqueue
wakeup is FIFO, so any other request will eventually arrive. Could you
explain this bug a bit better?

> If you think I should delay those fixes to do something else I don't
> agree sorry.

no, i never ment it. I find it very good that those half-done changes are
cleaned up and the remaining bugs / performance problems are eliminated -
the first reports about bad write performance came right after the
original elevator patches went in, about 6 months ago.

Ingo