While fp-stress is waiting for children to start it doesn't send any
signals to them so there is no need for it to have as short an epoll()
timeout as it does when the children are all running. We do still want to
have some timeout so that we can log diagnostics about missing children but
this can be relatively large. On emulated platforms the overhead of running
the supervisor process is quite high, especially during the process of
execing the test binaries.

Implement a longer epoll() timeout during the setup phase, using a 5s
timeout while waiting for children and switching  to the signal raise
interval when all the children are started and we start sending signals.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/arm64/fp/fp-stress.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/arm64/fp/fp-stress.c b/tools/testing/selftests/arm64/fp/fp-stress.c
index c986c68fbcacdd295f4db57277075209193cb943..963e2d891ced72fb8d6eff4fdb5c7df0724b14f1 100644
--- a/tools/testing/selftests/arm64/fp/fp-stress.c
+++ b/tools/testing/selftests/arm64/fp/fp-stress.c
@@ -453,6 +453,7 @@ int main(int argc, char **argv)
 {
 	int ret;
 	int timeout = 10 * (1000 / SIGNAL_INTERVAL_MS);
+	int poll_interval = 5000;
 	int cpus, i, j, c;
 	int sve_vl_count, sme_vl_count;
 	bool all_children_started = false;
@@ -588,7 +589,7 @@ int main(int argc, char **argv)
 		 * especially useful in emulation where we will both
 		 * be slow and likely to have a large set of VLs.
 		 */
-		ret = epoll_wait(epoll_fd, evs, tests, SIGNAL_INTERVAL_MS);
+		ret = epoll_wait(epoll_fd, evs, tests, poll_interval);
 		if (ret < 0) {
 			if (errno == EINTR)
 				continue;
@@ -626,6 +627,7 @@ int main(int argc, char **argv)
 			}
 
 			all_children_started = true;
+			poll_interval = SIGNAL_INTERVAL_MS;
 		}
 
 		if ((timeout % LOG_INTERVALS) == 0)

-- 
2.39.2

Nit: the title says we lower the poll interval, while we actually raise
it. Maybe that'd be clearer as:

	kselftest/arm64: Raise poll timeout while waiting for fp-stress children

... or:

	kselftest/arm64: Poll less frequently while waiting for fp-stress children

That aside, this looks fine.

Mark.

On Tue, Oct 29, 2024 at 12:10:40AM +0000, Mark Brown wrote:
> While fp-stress is waiting for children to start it doesn't send any
> signals to them so there is no need for it to have as short an epoll()
> timeout as it does when the children are all running. We do still want to
> have some timeout so that we can log diagnostics about missing children but
> this can be relatively large. On emulated platforms the overhead of running
> the supervisor process is quite high, especially during the process of
> execing the test binaries.
> 
> Implement a longer epoll() timeout during the setup phase, using a 5s
> timeout while waiting for children and switching  to the signal raise
> interval when all the children are started and we start sending signals.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>  tools/testing/selftests/arm64/fp/fp-stress.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/arm64/fp/fp-stress.c b/tools/testing/selftests/arm64/fp/fp-stress.c
> index c986c68fbcacdd295f4db57277075209193cb943..963e2d891ced72fb8d6eff4fdb5c7df0724b14f1 100644
> --- a/tools/testing/selftests/arm64/fp/fp-stress.c
> +++ b/tools/testing/selftests/arm64/fp/fp-stress.c
> @@ -453,6 +453,7 @@ int main(int argc, char **argv)
>  {
>  	int ret;
>  	int timeout = 10 * (1000 / SIGNAL_INTERVAL_MS);
> +	int poll_interval = 5000;
>  	int cpus, i, j, c;
>  	int sve_vl_count, sme_vl_count;
>  	bool all_children_started = false;
> @@ -588,7 +589,7 @@ int main(int argc, char **argv)
>  		 * especially useful in emulation where we will both
>  		 * be slow and likely to have a large set of VLs.
>  		 */
> -		ret = epoll_wait(epoll_fd, evs, tests, SIGNAL_INTERVAL_MS);
> +		ret = epoll_wait(epoll_fd, evs, tests, poll_interval);
>  		if (ret < 0) {
>  			if (errno == EINTR)
>  				continue;
> @@ -626,6 +627,7 @@ int main(int argc, char **argv)
>  			}
>  
>  			all_children_started = true;
> +			poll_interval = SIGNAL_INTERVAL_MS;
>  		}
>  
>  		if ((timeout % LOG_INTERVALS) == 0)
> 
> -- 
> 2.39.2
>