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SubjectRe: [patch] x86: allow ZONE_DMA to be configurable
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How do you know it is not a fatal condition?

"David Rientjes" <rientjes@google.com> wrote:

>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.

--
Sent from my mobile phone. Please pardon any lack of formatting.


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