linux-kernel - Re: [PATCH] x86: Deinline cpuid

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Message-ID: <554A649C.8070605@zytor.com>
Date:	Wed, 06 May 2015 11:59:40 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Denys Vlasenko <dvlasenk@...hat.com>,
	Ingo Molnar <mingo@...nel.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...capital.net>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Deinline cpuid_eax and friends

On 05/06/2015 10:07 AM, Denys Vlasenko wrote:
> cpuid_e{a,b,c,d}x() functions compile to 44 bytes of machine code each.
> On x86 allyesconfig build they have 48 callsites.
> Deinlining all four of them shrinks kernel by about 1k:
> 
>    text      data      bss       dec     hex filename
> 82434909 22255384 20627456 125317749 7783275 vmlinux.before
> 82433898 22255384 20627456 125316738 7782e82 vmlinux
> 
> Speed impact: CPUID instruction takes from 50 to 350+ cycles,
> call overhead is negligible in comparison.

How on Earth does it make 44 bytes?  Is this due to paravirt_fail?

	-hpa


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