Re: [PATCH 02/22 -v7] Add basic support for gcc profiler instrumentation

[Jan Kiszka]

Steven Rostedt wrote:

> --- linux-mcount.git.orig/arch/x86/kernel/entry_32.S	2008-01-29 16:59:15.000000000 -0500
> +++ linux-mcount.git/arch/x86/kernel/entry_32.S	2008-01-29 17:26:18.000000000 -0500
> @@ -75,6 +75,31 @@ DF_MASK		= 0x00000400 
>  NT_MASK		= 0x00004000
>  VM_MASK		= 0x00020000
>  
> +#ifdef CONFIG_MCOUNT
> +.globl mcount
> +mcount:
> +	/* unlikely(mcount_enabled) */
> +	cmpl $0, mcount_enabled
> +	jnz trace
> +	ret

(and the corresponding 64-bit version)

Is the impact of this change on the (already expensive) mcount_enabled
case negligible? I worried about use cases where we want to gain some
(relative) worst-case numbers via these instrumentations.

In my personal priority scheme, CONFIG_MCOUNT=y && !mcount_enabled comes
after mcount_enabled.

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/