From: Adrian Bunk <bunk@stusta.de>
To: jdike@karaya.com
Cc: linux-kernel@vger.kernel.org,
user-mode-linux-devel@lists.sourceforge.net
Subject: [uml-devel] UML and fastcall/FASTCALL
Date: Fri, 8 Dec 2006 13:59:28 +0100 [thread overview]
Message-ID: <20061208125928.GA25427@stusta.de> (raw)
UML on i386 is now the only case where fastcall/FASTCALL is not a noop.
There are two use cases for fastcall/FASTCALL in UML on i386:
1. optimization for C code
A faster calling convention is used for the functions annotated this way.
2. interfacing with assembler code
But include/asm-um/linkage.h contains the following:
<-- snip -->
#ifndef __ASM_UM_LINKAGE_H
#define __ASM_UM_LINKAGE_H
#include "asm/arch/linkage.h"
/* <linux/linkage.h> will pick sane defaults */
#ifdef CONFIG_GPROF
#undef FASTCALL
#undef fastcall
#endif
#endif
<-- snip -->
E.g. if CONFIG_SMP was still available on UML, CONFIG_SMP=y,
CONFIG_GPROF=y would have some horrible effects when calling the
functions in arch/i386/lib/semaphore.S.
Are there any benchmark numbers that the existing fastcall/FASTCALL
annotations in the kernel really make a measurable difference for
C code?
Otherwise, we could use it only for assembler code using this calling
convention (if there is any used by UML) - and CONFIG_GPROF mustn't
change this.
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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WARNING: multiple messages have this Message-ID (diff)
From: Adrian Bunk <bunk@stusta.de>
To: jdike@karaya.com
Cc: user-mode-linux-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: UML and fastcall/FASTCALL
Date: Fri, 8 Dec 2006 13:59:28 +0100 [thread overview]
Message-ID: <20061208125928.GA25427@stusta.de> (raw)
UML on i386 is now the only case where fastcall/FASTCALL is not a noop.
There are two use cases for fastcall/FASTCALL in UML on i386:
1. optimization for C code
A faster calling convention is used for the functions annotated this way.
2. interfacing with assembler code
But include/asm-um/linkage.h contains the following:
<-- snip -->
#ifndef __ASM_UM_LINKAGE_H
#define __ASM_UM_LINKAGE_H
#include "asm/arch/linkage.h"
/* <linux/linkage.h> will pick sane defaults */
#ifdef CONFIG_GPROF
#undef FASTCALL
#undef fastcall
#endif
#endif
<-- snip -->
E.g. if CONFIG_SMP was still available on UML, CONFIG_SMP=y,
CONFIG_GPROF=y would have some horrible effects when calling the
functions in arch/i386/lib/semaphore.S.
Are there any benchmark numbers that the existing fastcall/FASTCALL
annotations in the kernel really make a measurable difference for
C code?
Otherwise, we could use it only for assembler code using this calling
convention (if there is any used by UML) - and CONFIG_GPROF mustn't
change this.
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
next reply other threads:[~2006-12-08 13:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-08 12:59 Adrian Bunk [this message]
2006-12-08 12:59 ` UML and fastcall/FASTCALL Adrian Bunk
2006-12-08 16:33 ` [uml-devel] " Jeff Dike
2006-12-08 16:33 ` Jeff Dike
2006-12-08 18:04 ` [uml-devel] " Adrian Bunk
2006-12-08 18:04 ` Adrian Bunk
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