Re: [PATCH 1/4] Attribute method inlining

Hannes Domani
2020-05-21T01:08:43Z

Am Mittwoch, 20. Mai 2020, 19:40:44 MESZ hat Tom Tromey <tromey@adacore.com> Folgendes geschrieben:

> I ran gdb 10 times like:
>
>       /bin/time -f %e \
>             ./gdb/gdb --data-directory ./gdb/data-directory -nx \
>             -iex 'set debug-file-directory /usr/lib/debug' \
>             -batch $X
>
> ... where $X was the test executable.  Then I computed the mean time.
> This was all done with a standard (-g -O2) build of gdb.
>
> The baseline times were
>
> gdb    1.90
> libxul 2.12
> Ada    2.61
>
> This patch brings the numbers down to
>
> gdb    1.88
> libxul 2.11
> Ada    2.60

When I saw this, I thought I could do a similar profiling test on Windows (but
only with gdb itself).

So just: gdb.exe -q -batch gdb.exe

And I was a bit suprised to see that strcmp_iw_ordered (called from
sort_pst_symbols -> std::sort) is in ~24% of the profiling samples.
And only because of the functions isspace and tolower.

So I made a simple test, and added this before strcmp_iw_ordered:

static inline int isspace2 (int c)
{
return c == 0x20 || (c >= 0x09 && c <= 0x0d);
}
#define isspace isspace2

static inline int tolower2 (int c)
{
return (c >= 'A' && c <= 'Z') ? c + 0x20 : c;
}
#define tolower tolower2

And the mean time went from 3.7s down to 2.7s.

I'm not saying this is a correct solution, but does strcmp_iw_ordered have to
support anything besides the "C" locale?

Also, are isspace and tolower only on Windows a bottleneck?

(If anyone wants to see them, I can provide some profiler flame-graphs)

Hannes