Re: [PATCH 1/2] x86/mce: Pack boolean MCE boot flags into a structure

[Andi Kleen]

On Mon, Aug 27, 2012 at 04:55:03PM +0530, Naveen N. Rao wrote:
> Many MCE boot flags are boolean in nature, but are declared as integers
> currently. We can pack these into a bitfield to save some space.

Note that this doesn't necessarily save anything because it needs more
code to access, and accesses are more common than the flag

	cmpl  $0,foo(%rip)            7 bytes
        testl $1,foo(%rip)           10 bytes
        bt    $0,foo(%rip)            8 bytes

Even worse for writes. The best you can usually do is to use chars on
x86.

-Andi
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