linux-kernel - Re: [PATCH v3 4/4] x86/mce: Avoid unnecessary padding in struct mce

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Message-ID: <YhUC+T44sQK43+QZ@zn.tnic>
Date:   Tue, 22 Feb 2022 16:36:25 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
Cc:     x86@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        James Morse <james.morse@....com>,
        Robert Richter <rric@...nel.org>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: Re: [PATCH v3 4/4] x86/mce: Avoid unnecessary padding in struct
 mce_bank

On Fri, Feb 11, 2022 at 04:34:42PM -0600, Smita Koralahalli wrote:
> Include struct mce_bank member "init" in the bitfield by changing its type
> from bool to get rid of unnecessary padding and to reduce the overall
> struct size.
> 
> Outputs collected before and after the change.
> 
> $ pahole -C mce_bank arch/x86/kernel/cpu/mce/core.o
> 
> before:
> 
> 	/* size: 24, cachelines: 1, members: 5 */
> 	/* bit holes: 1, sum bit holes: 62 bits */
> 	/* bit_padding: 2 bits */
> 	/* last cacheline: 24 bytes */
> 
> after:
> 
> 	/* size: 16, cachelines: 1, members: 5 */
> 	/* last cacheline: 16 bytes */

I don't mind cleanups like that but when you send them as part of a set
adding new functionality, the usual rule is to put bug fixes, cleanups,
improvements, etc to the existing code *first*, and then, ontop you add
your new code.

IOW, this patch should be first in your set.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette