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From: Brian Gerst <brgerst@gmail.com>
To: Borislav Petkov <bp@suse.de>
Cc: "the arch/x86 maintainers" <x86@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init
Date: Mon, 18 Jan 2016 11:52:34 -0500	[thread overview]
Message-ID: <CAMzpN2i+LELbLaBbxDS0MF1Y0sn_Jm3ztCWATzMyrp4rnhWRQA@mail.gmail.com> (raw)
In-Reply-To: <20160117103337.GC8549@pd.tnic>

On Sun, Jan 17, 2016 at 5:33 AM, Borislav Petkov <bp@suse.de> wrote:
> On Sat, Jan 16, 2016 at 02:58:21PM -0500, Brian Gerst wrote:
>> It saves space.  The only thing left in main text is one jump
>> instruction (5 bytes).
>
> How do I measure this?
>
> Because with my tailored config here, the only thing I'm seeing is a growth of
> text by 730 bytes:
>
> before:
>    text    data     bss     dec     hex filename
> 10926552        3598944 16642048        31167544        1db9438 vmlinux
>
> [    0.056552] Freeing SMP alternatives memory: 24K (ffffffff81dd7000 - ffffffff81ddd000)
> [    2.883728] Freeing unused kernel memory: 2904K (ffffffff81b01000 - ffffffff81dd7000)
>
>
> after:
>    text    data     bss     dec     hex filename
> 10927282        3598944 16642048        31168274        1db9712 vmlinux
>
> [    0.052559] Freeing SMP alternatives memory: 24K (ffffffff81dd7000 - ffffffff81ddd000)
> [    3.225318] Freeing unused kernel memory: 2904K (ffffffff81b01000 - ffffffff81dd7000)

It is due to page alignment padding.  It was not enough to lose a
whole page from .text in your case.

The size command includes any section that is marked executable in the
text count, including init text.  If you use readelf -S vmlinux.o
instead you will notice that .text is the same size or smaller, and
.static_cpu_has (which is freed after boot) is the difference.

--
Brian Gerst

  reply	other threads:[~2016-01-18 16:52 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-16 19:22 [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst
2016-01-16 19:36 ` Borislav Petkov
2016-01-16 19:58   ` Brian Gerst
2016-01-17 10:33     ` Borislav Petkov
2016-01-18 16:52       ` Brian Gerst [this message]
2016-01-18 17:49         ` Andy Lutomirski
2016-01-18 18:14         ` Borislav Petkov
2016-01-18 18:29           ` Andy Lutomirski
2016-01-18 18:39             ` Borislav Petkov
2016-01-18 19:45               ` H. Peter Anvin
2016-01-18 23:05                 ` Borislav Petkov
2016-01-18 23:13                   ` H. Peter Anvin
2016-01-18 23:25                     ` Borislav Petkov
2016-01-19 13:57                       ` Borislav Petkov
2016-01-19 16:23                         ` Borislav Petkov
2016-01-19 23:10                         ` Borislav Petkov
2016-01-19 23:26                           ` Andy Lutomirski
2016-01-19 23:49                             ` Boris Petkov
2016-01-20  4:03                         ` H. Peter Anvin
2016-01-20 10:33                           ` Borislav Petkov
2016-01-20 10:41                             ` H. Peter Anvin
2016-01-21 22:14                               ` Borislav Petkov
2016-01-21 22:22                                 ` H. Peter Anvin
2016-01-21 22:56                                   ` Borislav Petkov
2016-01-21 23:36                                     ` H. Peter Anvin
2016-01-21 23:37                                     ` H. Peter Anvin
2016-01-22 10:32                                       ` Borislav Petkov
2016-01-18 18:51           ` Borislav Petkov
2016-01-19  1:10             ` Borislav Petkov
2016-01-19  1:33               ` H. Peter Anvin
2016-01-19  9:22                 ` Borislav Petkov
2016-01-20  4:02                   ` H. Peter Anvin
2016-01-20  4:39                     ` Brian Gerst
2016-01-20  4:42                       ` H. Peter Anvin
2016-01-20 10:50                         ` Borislav Petkov
2016-01-20 10:55                           ` H. Peter Anvin
2016-01-20 11:05                             ` Borislav Petkov
2016-01-20 14:48                               ` H. Peter Anvin
2016-01-20 15:01                     ` Borislav Petkov
2016-01-20 15:09                       ` H. Peter Anvin
2016-01-20 16:04                         ` Borislav Petkov
2016-01-20 16:16                           ` H. Peter Anvin
2016-01-23  6:50 [PATCH] x86/head_64.S: do not use temporary register to check alignment Alexander Kuleshov
2016-01-26  9:31 ` Borislav Petkov
2016-01-26 21:12 [PATCH 00/10] tip-queue 2016-01-26, rest Borislav Petkov
2016-01-26 21:12 ` [PATCH 01/10] x86/asm: Add condition codes clobber to memory barrier macros Borislav Petkov
2016-01-26 21:12 ` [PATCH 02/10] x86/asm: Drop a comment left over from X86_OOSTORE Borislav Petkov
2016-01-26 21:12 ` [PATCH 03/10] x86/asm: Tweak the comment about wmb() use for IO Borislav Petkov
2016-01-26 21:12 ` [PATCH 04/10] x86/cpufeature: Carve out X86_FEATURE_* Borislav Petkov
2016-01-30 13:18   ` [tip:x86/asm] " tip-bot for Borislav Petkov
2016-01-26 21:12 ` [PATCH 05/10] x86/cpufeature: Replace the old static_cpu_has() with safe variant Borislav Petkov
2016-01-30 13:19   ` [tip:x86/asm] " tip-bot for Borislav Petkov
2016-01-26 21:12 ` [PATCH 06/10] x86/cpufeature: Get rid of the non-asm goto variant Borislav Petkov
2016-01-27  3:36   ` Brian Gerst
2016-01-27  8:41     ` Borislav Petkov
2016-01-27  8:43       ` [PATCH -v1.1 " Borislav Petkov
2016-01-30 13:19         ` [tip:x86/asm] " tip-bot for Borislav Petkov
2016-01-27  8:45       ` [PATCH -v1.1 8/10] x86/alternatives: Discard dynamic check after init Borislav Petkov
2016-01-30 13:20         ` [tip:x86/asm] " tip-bot for Brian Gerst
2016-01-26 21:12 ` [PATCH 07/10] x86/alternatives: Add an auxilary section Borislav Petkov
2016-01-30 13:19   ` [tip:x86/asm] " tip-bot for Borislav Petkov
2016-01-26 21:12 ` [PATCH 08/10] x86/alternatives: Discard dynamic check after init Borislav Petkov
2016-01-26 21:12 ` [PATCH 09/10] x86/vdso: Use static_cpu_has() Borislav Petkov
2016-01-30 13:20   ` [tip:x86/asm] " tip-bot for Borislav Petkov
2016-01-26 21:12 ` [PATCH 10/10] x86/head_64: Simplify kernel load address alignment check Borislav Petkov
2016-01-30 13:20   ` [tip:x86/boot] x86/boot: " tip-bot for Alexander Kuleshov

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