Re: 3.5G user space speed

Brian Gerst
2002-01-15T21:06:20Z

Peter Zaitsev wrote:
>
> Hello Linux,
>
> 2.4.xaa Series as well as SuSE kernels have 3.5G userspace option,
> which seems to be quite useful, therefore I see it's not included
> is stock kernel for some reasons. Also I've heard this
> configuration may have some performance problems.
>
> Can anyone comment on this topic ?
>
> I need large amount of address space for my application but I also
> need to get as much I/O performance as it's possible, so I can switch
> to 3.0/1.0 memory distribution if it will benefit here.

You can't have it both ways with the x86 (speed vs. large userspace).
Kernel 2.5 may help a bit here because changes were made to allow DMA
from all memory (subject to card limitations), lessening the burden for
direct-mapped memory. Otherwise you'll need to move to a 64-bit arch.

--

Brian Gerst