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Date: Sat, 05 Jan 2008 16:16:47 +0300
From: Dmitri Vorobiev <dmitri.vorobiev@...il.com>
To: Arjan van de Ven <arjan@...ux.intel.com>
CC: linux-kernel@...r.kernel.org, mingo@...e.hu,
akpm@...ux-foundation.org, olof@...om.net, mpm@...enic.com
Subject: Re: [patch 1/2] move WARN_ON() out of line
Arjan van de Ven пишет:
> Subject: move WARN_ON() out of line
> From: Arjan van de Ven <arjan@...ux.intel.com>
> CC: Ingo Molnar <mingo@...e.hu>
> CC: Andrew Morton <akpm@...ux-foundation.org>
> CC: Olof Johansson <olof@...om.net>
> CC: Matt Meckall <mpm@...enic.com>
>
> A quick grep shows that there are currently 1145 instances of WARN_ON
> in the kernel. Currently, WARN_ON is pretty much entirely inlined,
> which makes it hard to enhance it without growing the size of the kernel
> (and getting Andrew rightfully unhappy).
>
> This patch build on top of Olof's patch that introduces __WARN,
> and places the slowpath out of line. It also uses Ingo's suggestion
> to not use __FUNCTION__ but to use kallsyms to do the lookup;
> this saves a ton of extra space since gcc doesn't need to store the
> function
> string twice now:
>
> 3936367 833603 624736 5394706 525112 vmlinux.before
> 3917508 833603 624736 5375847 520767 vmlinux-slowpath
>
> 15Kb savings...
>
This looks twice as good for one of MIPS configs:
text data bss dec hex filename
4908276 204104 2846304 7958684 79709c vmlinux.after
4941596 204104 2846304 7992004 79f2c4 vmlinux.before
$ file vmlinux
vmlinux: ELF 32-bit MSB executable, MIPS, version 1 (SYSV), statically linked, not stripped
More than 30Kb gone, thanks a lot!
Tested-by: Dmitri Vorobiev <dmitri.vorobiev@...il.com>
> Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
>
>
> ---
> include/asm-generic/bug.h | 7 ++-----
> kernel/panic.c | 14 ++++++++++++++
> 2 files changed, 16 insertions(+), 5 deletions(-)
>
> Index: linux-2.6.24-rc6/include/asm-generic/bug.h
> ===================================================================
> --- linux-2.6.24-rc6.orig/include/asm-generic/bug.h
> +++ linux-2.6.24-rc6/include/asm-generic/bug.h
> @@ -32,11 +32,8 @@ struct bug_entry {
> #endif
>
> #ifndef __WARN
> -#define __WARN() do { \
> - printk("WARNING: at %s:%d %s()\n", __FILE__, \
> - __LINE__, __FUNCTION__); \
> - dump_stack(); \
> -} while (0)
> +extern void warn_on_slowpath(const char *file, const int line);
> +#define __WARN() warn_on_slowpath(__FILE__, __LINE__)
> #endif
>
> #ifndef WARN_ON
> Index: linux-2.6.24-rc6/kernel/panic.c
> ===================================================================
> --- linux-2.6.24-rc6.orig/kernel/panic.c
> +++ linux-2.6.24-rc6/kernel/panic.c
> @@ -20,6 +20,7 @@
> #include <linux/kexec.h>
> #include <linux/debug_locks.h>
> #include <linux/random.h>
> +#include <linux/kallsyms.h>
>
> int panic_on_oops;
> int tainted;
> @@ -292,6 +293,19 @@ void oops_exit(void)
> (unsigned long long)oops_id);
> }
>
> +
> +void warn_on_slowpath(const char *file, int line)
> +{
> + char function[KSYM_SYMBOL_LEN];
> + unsigned long caller = (unsigned long) __builtin_return_address(0);
> +
> + sprint_symbol(function, caller);
> + printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
> + line, function);
> + dump_stack();
> +}
> +EXPORT_SYMBOL(warn_on_slowpath);
> +
> #ifdef CONFIG_CC_STACKPROTECTOR
> /*
> * Called when gcc's -fstack-protector feature is used, and
>
>
> ------------------------------------------------------------------------
>
> Subject: move WARN_ON() out of line
> From: Arjan van de Ven <arjan@...ux.intel.com>
> CC: Ingo Molnar <mingo@...e.hu>
> CC: Andrew Morton <akpm@...ux-foundation.org>
> CC: Olof Johansson <olof@...om.net>
> CC: Matt Meckall <mpm@...enic.com>
>
> A quick grep shows that there are currently 1145 instances of WARN_ON
> in the kernel. Currently, WARN_ON is pretty much entirely inlined,
> which makes it hard to enhance it without growing the size of the kernel
> (and getting Andrew unhappy).
>
> This patch build on top of Olof's patch that introduces __WARN,
> and places the slowpath out of line. It also uses Ingo's suggestion
> to not use __FUNCTION__ but to use kallsyms to do the lookup;
> this saves a ton of extra space since gcc doesn't need to store the function
> string twice now:
>
> 3936367 833603 624736 5394706 525112 vmlinux.before
> 3917508 833603 624736 5375847 520767 vmlinux-slowpath
>
> 15Kb savings...
>
> Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
>
>
> ---
> include/asm-generic/bug.h | 7 ++-----
> kernel/panic.c | 14 ++++++++++++++
> 2 files changed, 16 insertions(+), 5 deletions(-)
>
> Index: linux-2.6.24-rc6/include/asm-generic/bug.h
> ===================================================================
> --- linux-2.6.24-rc6.orig/include/asm-generic/bug.h
> +++ linux-2.6.24-rc6/include/asm-generic/bug.h
> @@ -32,11 +32,8 @@ struct bug_entry {
> #endif
>
> #ifndef __WARN
> -#define __WARN() do { \
> - printk("WARNING: at %s:%d %s()\n", __FILE__, \
> - __LINE__, __FUNCTION__); \
> - dump_stack(); \
> -} while (0)
> +extern void warn_on_slowpath(const char *file, const int line);
> +#define __WARN() warn_on_slowpath(__FILE__, __LINE__)
> #endif
>
> #ifndef WARN_ON
> Index: linux-2.6.24-rc6/kernel/panic.c
> ===================================================================
> --- linux-2.6.24-rc6.orig/kernel/panic.c
> +++ linux-2.6.24-rc6/kernel/panic.c
> @@ -20,6 +20,7 @@
> #include <linux/kexec.h>
> #include <linux/debug_locks.h>
> #include <linux/random.h>
> +#include <linux/kallsyms.h>
>
> int panic_on_oops;
> int tainted;
> @@ -292,6 +293,19 @@ void oops_exit(void)
> (unsigned long long)oops_id);
> }
>
> +
> +void warn_on_slowpath(const char *file, int line)
> +{
> + char function[KSYM_SYMBOL_LEN];
> + unsigned long caller = (unsigned long) __builtin_return_address(0);
> +
> + sprint_symbol(function, caller);
> + printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
> + line, function);
> + dump_stack();
> +}
> +EXPORT_SYMBOL(warn_on_slowpath);
> +
> #ifdef CONFIG_CC_STACKPROTECTOR
> /*
> * Called when gcc's -fstack-protector feature is used, and
--
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