When everything is starting up we are likely to have a lot of child processes producing output at once. This means that we can reduce overhead a bit by allowing epoll_wait() to return more than one descriptor at once, it cuts down on the number of system calls we need to do which on virtual platforms where the syscall overhead is a bit more noticable and we're likely to have a lot more children active can make a small but noticable difference.
On physical platforms the relatively small number of processes being run and vastly improved speeds push the effects of this change into the noise.
Signed-off-by: Mark Brown broonie@kernel.org --- tools/testing/selftests/arm64/fp/fp-stress.c | 27 +++++++++++++------- 1 file changed, 18 insertions(+), 9 deletions(-)
diff --git a/tools/testing/selftests/arm64/fp/fp-stress.c b/tools/testing/selftests/arm64/fp/fp-stress.c index b3bbfe8d9f56..f8b2f41aac36 100644 --- a/tools/testing/selftests/arm64/fp/fp-stress.c +++ b/tools/testing/selftests/arm64/fp/fp-stress.c @@ -39,6 +39,8 @@ struct child_data {
static int epoll_fd; static struct child_data *children; +static struct epoll_event *evs; +static int tests; static int num_children; static bool terminate;
@@ -393,11 +395,11 @@ static void probe_vls(int vls[], int *vl_count, int set_vl) /* Handle any pending output without blocking */ static void drain_output(bool flush) { - struct epoll_event ev; int ret = 1; + int i;
while (ret > 0) { - ret = epoll_wait(epoll_fd, &ev, 1, 0); + ret = epoll_wait(epoll_fd, evs, tests, 0); if (ret < 0) { if (errno == EINTR) continue; @@ -405,8 +407,8 @@ static void drain_output(bool flush) strerror(errno), errno); }
- if (ret == 1) - child_output(ev.data.ptr, ev.events, flush); + for (i = 0; i < ret; i++) + child_output(evs[i].data.ptr, evs[i].events, flush); } }
@@ -419,12 +421,11 @@ int main(int argc, char **argv) { int ret; int timeout = 10; - int cpus, tests, i, j, c; + int cpus, i, j, c; int sve_vl_count, sme_vl_count, fpsimd_per_cpu; bool all_children_started = false; int seen_children; int sve_vls[MAX_VLS], sme_vls[MAX_VLS]; - struct epoll_event ev; struct sigaction sa;
while ((c = getopt_long(argc, argv, "t:", options, NULL)) != -1) { @@ -510,6 +511,11 @@ int main(int argc, char **argv) ksft_print_msg("Failed to install SIGCHLD handler: %s (%d)\n", strerror(errno), errno);
+ evs = calloc(tests, sizeof(*evs)); + if (!evs) + ksft_exit_fail_msg("Failed to allocated %d epoll events\n", + tests); + for (i = 0; i < cpus; i++) { for (j = 0; j < fpsimd_per_cpu; j++) start_fpsimd(&children[num_children++], i, j); @@ -543,7 +549,7 @@ int main(int argc, char **argv) * useful in emulation where we will both be slow and * likely to have a large set of VLs. */ - ret = epoll_wait(epoll_fd, &ev, 1, 1000); + ret = epoll_wait(epoll_fd, evs, tests, 1000); if (ret < 0) { if (errno == EINTR) continue; @@ -552,8 +558,11 @@ int main(int argc, char **argv) }
/* Output? */ - if (ret == 1) { - child_output(ev.data.ptr, ev.events, false); + if (ret > 0) { + for (i = 0; i < ret; i++) { + child_output(evs[i].data.ptr, evs[i].events, + false); + } continue; }