Make nOS-V kernel overflow test configurable

test/rt/nosv/CMakeLists.txt

@@ -44,7 +44,6 @@ nosv_test(parallel-tasks.c SORT)
 nosv_test(inline.c SORT)
 nosv_test(mutex.c SORT LEVEL 3)
 nosv_test(barrier.c SORT LEVEL 3)
-nosv_test(overflow-kernel-ring.c SORT LEVEL 3)
 
 # Test multiple instrumentation levels
 nosv_test(several-tasks.c SORT NAME several-tasks-level-0 LEVEL 0)
@@ -63,3 +62,13 @@ nosv_test(several-tasks.c SORT NAME several-tasks-breakdown-level-2 LEVEL 2 BREA
 # From level 3 up the breakdown can be enabled
 nosv_test(several-tasks.c SORT NAME several-tasks-breakdown-level-3 LEVEL 3 BREAKDOWN)
 nosv_test(several-tasks.c SORT NAME several-tasks-breakdown-level-4 LEVEL 4 BREAKDOWN)
+
+include(CheckPerfParanoid)
+if (PERF_PARANOID_KERNEL)
+  message(STATUS "Enabling perf paranoid tests for nOS-V")
+  nosv_test(overflow-kernel-ring.c DRIVER "overflow-kernel-ring.driver.sh")
+elseif(ENABLE_ALL_TESTS)
+  message(FATAL_ERROR "Cannot enable perf paranoid tests for nOS-V")
+else()
+  message(STATUS "Disabling perf paranoid tests for nOS-V")
+endif()

test/rt/nosv/overflow-kernel-ring.c

@@ -5,47 +5,44 @@
 #include <nosv/affinity.h>
 #include <stdatomic.h>
 #include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
 
 #include "common.h"
 #include "compat.h"
 
 int done = 0;
-
-/* https://gitlab.bsc.es/nos-v/nos-v/-/blob/master/src/include/instr.h?ref_type=heads#L542 */
-#define NOSV_INSTR_KBUFLEN (4UL * 1024UL * 1024UL) // 4 MB
+unsigned long ncs = 0;
+unsigned long nflush = 0;
 
 static void
 task_run(nosv_task_t task)
 {
 	UNUSED(task);
 
-	/* Cause enough context switches for the kernel ring to be full,
-	 * which wouldn't fail if nosv_waitfor() flushes the kernel
-	 * events. */
-
-	unsigned long fill = 3 * NOSV_INSTR_KBUFLEN / 4;
-	unsigned long n = fill / 16;
-
 	struct timespec one_ns = { .tv_sec = 0, .tv_nsec = 1 };
 
-	for (unsigned long run = 0; run < 3; run++) {
-		info("starting run %lu", run);
-		for (unsigned long i = 0; i < n; i++)
+	for (unsigned long i = 1; i <= ncs; i++) {
 		nanosleep(&one_ns, NULL);
-
-		info("starting waitfor");
-
+		/* Make a total of 16 waitfor calls to flush the ring buffer */
+		if (i % nflush == 0) {
+			info("flusing at %lu", i);
 			if (nosv_waitfor(1, NULL) != 0)
 				die("nosv_waitfor failed");
-
-		info("end run %lu", run);
+		}
 	}
 
 	done = 1;
 }
 
-int main(void)
+int main(int argc, char *argv[])
 {
+	if (argc != 3)
+		die("usage: %s <num-cs> <num-flush>\n", argv[0]);
+
+	ncs = (unsigned long) atol(argv[1]);
+	nflush = (unsigned long) atol(argv[2]);
+
 	if (nosv_init())
 		die("nosv_init failed");
 

test/rt/nosv/overflow-kernel-ring.driver.sh

@@ -0,0 +1,46 @@
+target=$OVNI_TEST_BIN
+
+# We will set our own
+unset NOSV_CONFIG
+unset NOSV_CONFIG_OVERRIDE
+
+export NOSV_APPID=1
+
+# Small kernel ring size to make execution fast
+ringsize=$((64*1024))
+
+# Each CS event pair occupies 16 bytes.
+cspair=32
+
+# How many CS event pairs fit in the ring buffer?
+navail=$(($ringsize / $cspair))
+
+# For the test, write 8 times the ring buffer
+ncs=$((8 * $navail))
+
+# Flush the kernel after writing 1/4 of the ring buffer. 
+nflush=$(($ringsize / $cspair / 4))
+
+cat > nosv.toml << EOF
+instrumentation.version = "ovni"
+ovni.level = 3
+ovni.kernel_ringsize = ${ringsize}
+EOF
+
+$target $ncs $nflush 2>&1 | tee err.log
+
+# Ensure no nOS-V warnings at runtime
+if grep -c "cannot enable kernel events" err.log; then
+  echo "cannot enable kernel events in all threads" >&2
+  exit 1
+fi
+
+# We need to sort the trace as it has unsorted regions
+ovnisort ovni
+
+# Ensure we have at least the number of context switches we caused, and ensure
+# the number of "in" and "out" events match.
+ovnitop ovni | awk '{n[$1] = $2} END { if (n["KCO"] != n["KCI"] || n["KCO"] < '$ncs') exit 1 }'
+
+# Run the emulator
+ovniemu -l ovni