Re: [gnugo-devel] weird performance problem

[Arend Bayer]

Paul wrote:

> > Tracking back some spurious 50% slowdowns for regression runs,
> > I found out (with oprofile) that 50% of CPU time was spent in libc.

(...)

> > Profiling through timer interrupt
> > samples  %        symbol name
> > 6769     86.3393  __mcount_internal
> > 665       8.4821  mcount
> > 189       2.4107  __i686.get_pc_thunk.bx
> > 170       2.1684  memset
> > 27        0.3444  memcpy
> > 6         0.0765  _int_malloc
> > 3         0.0383  __GI___mbrtowc
> > 2         0.0255  _int_free
> > 1         0.0128  __GI___gettimeofday_internal
> > 1         0.0128  __GI__dl_mcount_wrapper_check
> > 1         0.0128  __malloc
> > 1         0.0128  __realloc
> > 1         0.0128  _int_realloc
> > 1         0.0128  _nl_explode_name
> > 1         0.0128  _nl_make_l10nflist
> > 1         0.0128  index
> > 1         0.0128  strlen
> 
> This is not very helpful.  Can't say anything without call tree.

Well if I had been able to produce a call graph, I would certainly
have done so.

> Btw, `libc' is not `glibc' i.e. not GNU libc, right?

No it is glibc: rpm -q -f /lib/libc.so.6
glibc-2.3.2-87

Actually, it (partially) turned out to be a sillyness of mine: I
had somehow carried around -pg in the Makefiles, and mcount() seems
to be the collecting point for gprof data.

Still, I got only <15% of CPU time for a gnugo that I had explicitly
compiled with -pg and -lc_p.

Arend