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 buffering a line's worth of pixels and writing that out in a single call. Signed-off-by: Avi Kivity <a...@redhat.com> --- v2: drop unportable fputc_unlocked hw/vga.c | 13 ++++++++++--- 1 files changed, 10 insertions(+), 3 deletions(-) diff --git a/hw/vga.c b/hw/vga.c index d5bc582..97c96bf 100644 --- a/hw/vga.c +++ b/hw/vga.c @@ -2349,15 +2349,19 @@ int ppm_save(const char *filename, struct DisplaySurface *ds) uint32_t v; int y, x; uint8_t r, g, b; + int ret; + char *linebuf, *pbuf; f = fopen(filename, "wb"); if (!f) return -1; fprintf(f, "P6\n%d %d\n%d\n", ds->width, ds->height, 255); + linebuf = qemu_malloc(ds->width * 3); d1 = ds->data; for(y = 0; y < ds->height; y++) { d = d1; + pbuf = linebuf; for(x = 0; x < ds->width; x++) { if (ds->pf.bits_per_pixel == 32) v = *(uint32_t *)d; @@ -2369,13 +2373,16 @@ 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); + *pbuf++ = r; + *pbuf++ = g; + *pbuf++ = b; d += ds->pf.bytes_per_pixel; } d1 += ds->linesize; + ret = fwrite(linebuf, 1, pbuf - linebuf, f); + (void)ret; } + qemu_free(linebuf); fclose(f); return 0; } -- 1.7.5.3