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

[William Lee Irwin III <wli@holomorphy.com>]

On Thu, Jun 24, 2004 at 08:02:56PM +0200, Andrea Arcangeli wrote:
> I'm talking to Andrew about this very issue since december 2002, so I
> mostly giveup except for a few reminders like this one today.
> http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&selm=20021206145718.GL1567%40dualathlon.random&prev=/groups%3Fq%3Dlinus%2Bgoogle%2Bfix%2Bmin%2Bwatermarks%26hl%3D
> I'm confident as people starts to run into the zone inbalance with 2.6
> and as google upgrades to 2.6, eventually lowmem_zone_reserve_ratio will
> be forward ported to 2.4.26 to 2.6.  I'm not the guy with >4G of ram
> anyways, so it won't be myself having troubles with this ;).
> Furthermore if you have some swap, the VM can normally relocate the
> stuff (you've to be quite unlucky to be filled by pure ptes in the
> lowmem zone but it can happen too, but certainly not in my or Andrew's
> boxes where we have not more than 2M of ptes anytime allocated).

This sounds like the more precise fix would be enforcing a stricter
fallback criterion for pinned allocations. Pinned userspace would need
zone migration if it's done selectively like this.

Thanks.


-- wli