Re: [discuss] Re: 32-bit dma allocations on 64-bit platforms

[Andrea Arcangeli <andrea@suse.de>]

On Thu, Jun 24, 2004 at 02:54:41PM -0700, Andrew Morton wrote:
> First thing to do is to identify some workload which needs the patch. 

that's quite trivial, boot a 2G box, malloc(1G), bzero(1GB), swapoff -a,
then the machine will lockup.

Depending on the architecture (more precisely depending if it starts
allocating ram from the end or from the start of the physical memory),
you may have to load 1G of data into pagecache first, like reading from
/dev/hda 1G (without closing the file) will work fine, then run the
above malloc + bzero + swapoff.

Most people will never report this because everybody has swap and they
simply run a lot slower than they could run if they didn't need to pass
through the swap device to relocate memory because memory would been allocated
in the right place in the first place. this plus the various oom killer
breakages that gets dominated by the nr_swap_pages > 0 check, are the
reasons 2.6 is unusable w/o swap.