Re: DMA memory shortage?
H. Peter Anvin (hpa@transmeta.com)
14 Dec 1998 02:25:25 GMT
Followup to: <Pine.LNX.3.96.981211212418.4789I-100000@quake-sv.novare.net>
By author: Adam Heath <doogie@debian.org>
In newsgroup: linux.dev.kernel
>
> On 10 Dec 1998, H. Peter Anvin wrote:
>
> > This is very common if you have large amounts of memory, since only
> > the first 16 MB is usable for ISA DMA. I think if you have enough
> > memory I think it is the right thing to save a pool of DMA-capable
> > pages for that purpose only; I have been meaning to implement such a
> > hack.
>
> Why? When there isn't enough dma pages available, but enough free mem, the
> kernel could move the pages into upper memory. that is the proper way.
>
> Adam
>
Moving pages is darn near impossible. It requires additional data
structures that would require lots of additional memory to maintain.
It's cheaper to keep a pool of DMA buffers on hand.
-hpa
--
PGP: 2047/2A960705 BA 03 D3 2C 14 A8 A8 BD 1E DF FE 69 EE 35 BD 74
See http://www.zytor.com/~hpa/ for web page and full PGP public key
I am Bahá'í -- ask me about it or see http://www.bahai.org/
"To love another person is to see the face of God." -- Les Misérables
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/