On Sun, 19 Jun 2011, Avi Kivity wrote:
CONFORMING TO
The four functions getc_unlocked(), getchar_unlocked(),
putc_unlocked(), putchar_unlocked() are in POSIX.1-2001.
The non-standard *_unlocked() variants occur on a few Unix systems, and
are available in recent glibc. They should probably not be used.
> When running kvm-autotest, fputc() is often the second highest (sometimes #1)
> function showing up in a profile. This is due to fputc() locking the file
> for every byte written.
>
> Optimize by using fputc_unlocked(). Since the file is local to the caller,
> clearly no locking is needed. According to the manual, _GNU_SOURCE is all
> that's needed for the function to be present.
>
> Signed-off-by: Avi Kivity <a...@redhat.com>
> ---
> hw/vga.c | 6 +++---
> 1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/vga.c b/hw/vga.c
> index d5bc582..8b63358 100644
> --- a/hw/vga.c
> +++ b/hw/vga.c
> @@ -2369,9 +2369,9 @@ int ppm_save(const char *filename, struct
> DisplaySurface *ds)
> (ds->pf.gmax + 1);
> b = ((v >> ds->pf.bshift) & ds->pf.bmax) * 256 /
> (ds->pf.bmax + 1);
> - fputc(r, f);
> - fputc(g, f);
> - fputc(b, f);
> + fputc_unlocked(r, f);
> + fputc_unlocked(g, f);
> + fputc_unlocked(b, f);
> d += ds->pf.bytes_per_pixel;
> }
> d1 += ds->linesize;
>
--
mailto:av1...@comtv.ru
