Re: [SCM] strace branch, master, updated. v4.6-115-g102ec49

[Dmitry V. L. <ld...@al...>]

On Wed, Aug 24, 2011 at 11:41:10PM +0000, Denys Vlasenko wrote:
> commit 102ec4935440ff52a7fa3566154a84cc2473f16a
> Author: Denys Vlasenko <dvl...@re...>
> Date:   Thu Aug 25 01:27:59 2011 +0200
> 
>     Optimize tabto()
>     
>     tabto is used in many lines of strace output.
>     On glibc, tprintf("%*s", col - curcol, "") is noticeably slow
>     compared to tprintf("                 "). Use the latter.
>     Observed ~15% reduction of time spent in userspace.
>     
>     * defs.h: Drop extern declaration of acolumn. Make tabto()
>     take no parameters.
>     * process.c (sys_exit): Call tabto() with no parameters.
>     * syscall.c (trace_syscall_exiting): Call tabto() with no parameters.
>     * strace.c: Make acolumn static, add static char *acolumn_spaces.
>     (main): Allocate acolumn_spaces as a string of spaces.
>     (printleader): Call tabto() with no parameters.
>     (tabto): Use simpler method to print lots of spaces.
[...]
>  void
> -tabto(int col)
> +tabto(void)
>  {
> -	if (curcol < col)
> -		tprintf("%*s", col - curcol, "");
> +	if (curcol < acolumn)
> +		tprintf(acolumn_spaces + curcol);
>  }

The new statement yields a warning:

strace.c: In function 'tabto':
strace.c:2701:3: warning: format not a string literal and no format arguments

Maybe we could use
		tprintf("%s", acolumn_spaces + curcol);
instead without performance degradation?


-- 
ldv