On Wed, Aug 24, 2011 at 11:41:10PM +0000, Denys Vlasenko wrote: > commit 102ec4935440ff52a7fa3566154a84cc2473f16a > Author: Denys Vlasenko <[email protected]> > 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?
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