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SubjectRe: mm: critical shortage of bounce buffers
Steffen Persvold wrote:
>
> Alan Cox wrote:
> >
> > > I've recently encountered the following message on a machine running RedHat's
> > > 2.4.3-12 kernel :
> > >
> > > "mm: critical shortage of bounce buffers"
> > >
> > > I've searched through the kernel sources, but my 'find' just can't locate this
> > > string anywhere.
> >
> > Its in the high mem handling routines. It means the machine stalled for
> > a moment doing I/O because it had no memory below 1Gb to use.
>
> But why does it need to have memory below 1Gb ?? Normally, 32bit PCI DMA
> controllers (such as network cards and disk controllers) can access up to 4GB of
> physical memory within the machine, so unless you are using the CONFIG_HIGHMEM4G
> option it shouldn't need bounce buffers.

Sorry that should have been the CONFIG_HIGHMEM64G option. I think the
CONFIG_HIGHMEM4G option could manage without bounce buffers.

Regards,
--
Steffen Persvold | Scalable Linux Systems | Try out the world's best
mailto:sp@scali.no | http://www.scali.com | performing MPI implementation:
Tel: (+47) 2262 8950 | Olaf Helsets vei 6 | - ScaMPI 1.12.2 -
Fax: (+47) 2262 8951 | N0621 Oslo, NORWAY | >300MBytes/s and <4uS latency
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