From 544e35785198045d76d8f11ee414c7f1661ffc77 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Thu, 10 May 2012 20:25:33 +0200 Subject: [PATCH] tests/gtt_speed: try to outwit gcc It optimized away the read loops ;-) Also fix up the size to not be 1/4th of the one we want for tiled buffer tests. Signed-Off-by: Daniel Vetter --- tests/gem_gtt_speed.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/tests/gem_gtt_speed.c b/tests/gem_gtt_speed.c index 8c66aee..69cd1ff 100644 --- a/tests/gem_gtt_speed.c +++ b/tests/gem_gtt_speed.c @@ -102,23 +102,29 @@ int main(int argc, char **argv) /* prefault into gtt */ { - uint32_t *ptr = gem_mmap(fd, handle, size, PROT_READ); + uint32_t *ptr = gem_mmap(fd, handle, size, PROT_READ | PROT_WRITE); int x = 0; for (i = 0; i < size/sizeof(*ptr); i++) x += ptr[i]; + /* force overtly clever gcc to actually compute x */ + ptr[0] = x; + munmap(ptr, size); } /* mmap read */ gettimeofday(&start, NULL); for (loop = 0; loop < 1000; loop++) { - uint32_t *ptr = gem_mmap(fd, handle, size, PROT_READ); + uint32_t *ptr = gem_mmap(fd, handle, size, PROT_READ | PROT_WRITE); int x = 0; for (i = 0; i < size/sizeof(*ptr); i++) x += ptr[i]; + /* force overtly clever gcc to actually compute x */ + ptr[0] = x; + munmap(ptr, size); } gettimeofday(&end, NULL); @@ -142,12 +148,15 @@ int main(int argc, char **argv) /* mmap read */ gettimeofday(&start, NULL); for (loop = 0; loop < 1000; loop++) { - uint32_t *ptr = gem_mmap(fd, handle, size, PROT_READ); + uint32_t *ptr = gem_mmap(fd, handle, size, PROT_READ | PROT_WRITE); int x = 0; for (i = 0; i < size/sizeof(*ptr); i++) x += ptr[i]; + /* force overtly clever gcc to actually compute x */ + ptr[0] = x; + munmap(ptr, size); } gettimeofday(&end, NULL); @@ -214,6 +223,8 @@ int main(int argc, char **argv) gettimeofday(&end, NULL); printf("Time to pread %dk through the GTT (clflush): %7.3fµs\n", size/1024, elapsed(&start, &end, loop)); + + size *= 4; } } -- 2.7.4