Messages in this thread | | | Date | Wed, 13 Oct 2010 17:49:53 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [patch] x86: allow ZONE_DMA to be configurable |
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On Wed, 13 Oct 2010, H. Peter Anvin wrote:
> > You can already set the lowmem_reserve_ratio via > > /proc/sys/vm/lowmem_reserve_ratio. > > And why is it then so hard to put in a single line in /etc/sysctl.conf > for you? >
Because disabling CONFIG_ZONE_DMA allows for additional extensions: disabling CONFIG_GENERIC_ISA_DMA and CONFIG_ISA_DMA_API. We've also run for a couple years without those.
> > We've run without ZONE_DMA for a couple years because we don't have such > > hardware limitations and would appreciate the ability to disable it with a > > config option rather than hacking the kernel to get it to compile. I'm > > sure Casey would as well as you can see in the thread "A question about > > ZONE_DMA". > > > > I don't see the harm in being able to conveniently disable the zone if you > > know what you're doing. > > There are going to be a lot of very strange bug reports as a result. >
We have config options all over the kernel that change the behavior of syscalls without worrying about bug reports popping up from users who knowingly have disabled the option, I don't see this as being any different. If you're concerned about, we could add a
#ifndef CONFIG_ZONE_DMA WARN_ON_ONCE(gfp_mask & __GFP_DMA); #endif
in the page allocator.
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