1.5.2 *does* exibit the problem. When I ran 1.5.2 kernel with "options
BUFCACHE=50" on a machine with 512M of RAM the system frequently was
unresponsive when there was a lot of disk activity. I played around
with BUFCACHE setting and had to bring it down to ~20 in order to make
system usable for interactive work.

This seems to confirm the theory that number of outstanding I/O
requests is what differentiates default 1.5.2 configuration with
fairly small buffer cache from 1.6 with UBC which can potentially be
very large.

--Artem


On Fri, Jun 21, 2002 at 12:56:18PM -0700, Jason R Thorpe <thorpej@wasabisystems.com> wrote:
> On Fri, Jun 21, 2002 at 03:44:37PM -0400, Gary Thorpe wrote:
> 
>  > Then why doesn't 1.5.2 exhibit the same problem???
> 
> Because pre-UBC systems won't ever have as much outstanding I/O
> because the buffer cache is a fixed size (and also much smaller).
> 
> -- 
>         -- Jason R. Thorpe <thorpej@wasabisystems.com>
>