Re: Machine's high load when HIGHMEM is enabled

Jens Axboe
2002-11-03T14:54:32Z

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.

--
Jens Axboe