linux-kernel - [PATCH v2 2/2] kselftest/arm64: Poll less often while waiting for fp-stress children

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Message-Id: <20241030-arm64-fp-stress-interval-v2-2-bd3cef48c22c@kernel.org>
Date: Wed, 30 Oct 2024 00:02:03 +0000
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>, 
 linux-arm-kernel@...ts.infradead.org, linux-kselftest@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: [PATCH v2 2/2] kselftest/arm64: Poll less often while waiting for
 fp-stress children

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@...nel.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 71d02c701bf56be56b7ad00a5f6614e33dc8e01b..4f1ef260ce7a26d24092fe9337714f8c3922070a 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