Re: Machine's high load when HIGHMEM is enabled

[Denis Vlasenko]

On 3 November 2002 13:00, Jens Axboe wrote:
> On Sun, Nov 03 2002, Brian Gerst wrote:
> > vasya vasyaev wrote:
> > >Hello,
> > >
> > >I have some strange kind of problem:
> > >When HIGHMEM-enabled kernel is used, there is too high
> > >CPU load on any task - computer get loaded high while
> > >it is doing some minor, usual jobs (load average grows
> > >significantly).
> >
> > 2.4 can only do I/O to and from lowmem.  This means highmem pages
> > have
>
> 2.4.19 and below, 2.4.20-pre/rc can dma to/from highmem pages just
> fine.
>
> > to use bounce buffers in lowmem, and th edata is copied to/from
> > highmem which is causing the cpu load.  This has been corrected in
> > 2.5, which can do I/O to any page the device can DMA from.
>
> I seriously doubt this is his problem, sounds like something else.
> For gzip to be disk bound (and thus bounce bound) you would need a
> seriously fast cpu. And the ssh problem cannot be explained by
> bouncing either.

bad mtrr?
--
vda