Messages in this thread | | | Date | Thu, 14 Oct 2010 01:10:56 -0700 | From | Andrew Morton <> | Subject | Re: [patch] x86: allow ZONE_DMA to be configurable |
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On Wed, 13 Oct 2010 17:15:04 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:
> ZONE_DMA is unnecessary for a large number of machines that do not > require addressing in the lower 16MB of memory because they do not use > ISA devices with 16-bit address registers (plus one page byte register). > > This patch allows users to disable ZONE_DMA for x86 if they know they > will not be using such devices with their kernel. > > This prevents the VM from unnecessarily reserving a ratio of memory > (defaulting to 1/256th of system capacity) with lowmem_reserve_ratio > for such allocations when it will never be used. >
I wonder how hard it would be to do this at runtime, probably with a boot parameter.
I'd be a little concerned at the effects of this on page reclaim and the page allocator - it might expose weird pre-existing bugs or inefficiencies. But we can cross that bridge when we fall off it, I guess.
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