Messages in this thread | | | Date | Wed, 13 Oct 2010 18:48:21 -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:
> And the value of those additional options is what? I'd consider adding > this to the sewer pit called CONFIG_EMBEDDED (with a BUG_ON, not a > warning... sheesh)
BUG_ON() could panic the machine which would be rather unfortunate if we simply tried to load a driver that the kernel no longer supports because it doesn't have DMA. A WARN_ON() seems much more appropriate to identify what the problem was. It's not a fatal condition.
> but only if there is any demonstrable value other > than a trivial amount of code (kilobytes?) in exchange for a bunch of > crap #ifdef. >
The data savings is about 1% and the text savings is about 0.1% with all three options disabled:
7922297 1245500 989600 10157397 9afd55 vmlinux.before 7914674 1232700 989472 10136846 9aad0e vmlinux.after
This is the only #ifdef necessary to make CONFIG_ZONE_DMA=n compile and CONFIG_GENERIC_ISA_DMA=n would require two additional #ifdefs (CONFIG_ISA_DMA_API=n would require none). We carry this patch internally, so it would be trivial to send follow-up patches that do that if this patch is merged.
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