linux-kernel - Re: [PATCH 2/3] x86/mce: Pack boolean MCE flags into a structure

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Date:	Thu, 06 Sep 2012 12:18:31 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	Tony Luck <tony.luck@...el.com>, bp@...64.org
CC:	andi@...stfloor.org, gong.chen@...ux.intel.com, ananth@...ibm.com,
	x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...hat.com,
	hpa@...or.com, tglx@...utronix.de, gregkh@...e.de,
	linux-edac@...r.kernel.org
Subject: Re: [PATCH 2/3] x86/mce: Pack boolean MCE flags into a structure

On 09/06/2012 12:26 AM, Tony Luck wrote:
> On Wed, Sep 5, 2012 at 3:22 AM, Naveen N. Rao
> <naveen.n.rao@...ux.vnet.ibm.com> wrote:
>> Many MCE flags are boolean in nature, but are declared as integers
>> currently. We can pack these into a bitfield to save some space.
>
> Before this patch:
> size arch/x86/kernel/cpu/mcheck/mce.o
>     text	   data	    bss	    dec	    hex	filename
>    18946	   4930	    776	  24652	   604c	arch/x86/kernel/cpu/mcheck/mce.o
>
> After:
> size arch/x86/kernel/cpu/mcheck/mce.o
>     text	   data	    bss	    dec	    hex	filename
>    19335	   4890	    776	  25001	   61a9	arch/x86/kernel/cpu/mcheck/mce.o
>
> So we do indeed see "data" reduced by 40 bytes. But
> "text" is up by 389.  This seems to be because you have
> another change, not described in the commit log, buried
> in part 2 to add get_dont_log_ce(), set_dont_log_ce() etc.
>
> Compiler version: gcc version 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC)
>
> I know I'm contradicting the feedback you got from Borislav here, but
> is this code churn really worth it to save 40 bytes? I don't think so.

Hmm.. I think I agree. I don't see a good way to get rid of the 
individual getters and setters without adding some more code churn. I 
guess using boolean would be better. Boris?


Thanks,
Naveen

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