On Wed, Jul 16 2003, Andrea Arcangeli wrote:
> On Tue, Jul 15, 2003 at 01:27:37PM +0200, Jens Axboe wrote:
> > On Tue, Jul 15 2003, Alan Cox wrote:
> > > On Maw, 2003-07-15 at 06:26, Jens Axboe wrote:
> > > > Sorry, but I think that is nonsense. This is the way we have always
> > > > worked. You just have to maintain a decent queue length still (like we
> > > > always have in 2.4) and there are no problems.
> > >
> > > The memory pinning problem is still real - and always has been. It shows up
> > > best not on IDE disks but large slow media like magneto opticals where you
> > > can queue lots of I/O but you get 500K/second
> >
> > Not the same thing. On slow media, like dvd-ram, what causes the problem
> > is that you can dirty basically all of the RAM in the system. That has
> > nothing to do with memory pinned in the request queue.
>
> you can trivially bound the amount of dirty memory to nearly 0% with the
> bdflush sysctl. And the overkill size of the queue until pre3 could be
> an huge VM overhead compared to the dirty memory on lowmem boxes,
> example a 32/64M machine. So I disagree it's only a mistake of write
> throttling that gives problems on slow media.
>
> Infact I tend to think the biggest problem for slow media in 2.4 is the
> lack of per spindle pdflush.
Well it's a combined problem. Threshold too high on dirty memory,
someone doing a read well get stuck flushing out as well.
-- Jens Axboe- 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/
This archive was generated by hypermail 2b29 : Wed Jul 23 2003 - 22:00:24 EST