perf tests: Add option to run tests in parallel

By default tests are forked, add an option (-p or --parallel) so that
the forked tests are all started in parallel and then their output
gathered serially. This is opt-in as running in parallel can cause
test flakes.

Rather than fork within the code, the start_command/finish_command
from libsubcmd are used. This changes how stderr and stdout are
handled. The child stderr and stdout are always read to avoid the
child blocking. If verbose is 1 (-v) then if the test fails the child
stdout and stderr are displayed. If the verbose is >1 (e.g. -vv) then
the stdout and stderr from the child are immediately displayed.

An unscientific test on my laptop shows the wall clock time for perf
test without parallel being 5 minutes 21 seconds and with parallel
(-p) being 1 minute 50 seconds.

Signed-off-by: Ian Rogers <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Justin Stitt <[e-mail]>
Cc: Bill Wendling <[e-mail]>
Cc: Nick Desaulniers <[e-mail]>
Cc: Yang Jihong <[e-mail]>
Cc: Nathan Chancellor <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Athira Jajeev <[e-mail]>
Cc: [e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

tools/perf/tests/builtin-test.c

···
  */
 #include <fcntl.h>
 #include <errno.h>
+#include <poll.h>
 #include <unistd.h>
 #include <string.h>
 #include <stdlib.h>
···
 #include "debug.h"
 #include "color.h"
 #include <subcmd/parse-options.h>
+#include <subcmd/run-command.h>
 #include "string2.h"
 #include "symbol.h"
 #include "util/rlimit.h"
+#include "util/strbuf.h"
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <subcmd/exec-cmd.h>
···
 
 #include "tests-scripts.h"
 
+/*
+ * Command line option to not fork the test running in the same process and
+ * making them easier to debug.
+ */
 static bool dont_fork;
+/* Fork the tests in parallel and then wait for their completion. */
+static bool parallel;
 const char *dso_to_test;
 const char *test_objdump_path = "objdump";
 
···
 	return false;
 }
 
-static int run_test(struct test_suite *test, int subtest)
+struct child_test {
+	struct child_process process;
+	struct test_suite *test;
+	int test_num;
+	int subtest;
+};
+
+static int run_test_child(struct child_process *process)
 {
-	int status, err = -1, child = dont_fork ? 0 : fork();
-	char sbuf[STRERR_BUFSIZE];
-
-	if (child < 0) {
-		pr_err("failed to fork test: %s\n",
-			str_error_r(errno, sbuf, sizeof(sbuf)));
-		return -1;
-	}
-
-	if (!child) {
-		if (!dont_fork) {
-			pr_debug("test child forked, pid %d\n", getpid());
-
-			if (verbose <= 0) {
-				int nullfd = open("/dev/null", O_WRONLY);
-
-				if (nullfd >= 0) {
-					close(STDERR_FILENO);
-					close(STDOUT_FILENO);
-
-					dup2(nullfd, STDOUT_FILENO);
-					dup2(STDOUT_FILENO, STDERR_FILENO);
-					close(nullfd);
-				}
-			} else {
-				signal(SIGSEGV, sighandler_dump_stack);
-				signal(SIGFPE, sighandler_dump_stack);
-			}
-		}
-
-		err = test_function(test, subtest)(test, subtest);
-		if (!dont_fork)
-			exit(err);
-	}
-
-	if (!dont_fork) {
-		wait(&status);
-
-		if (WIFEXITED(status)) {
-			err = (signed char)WEXITSTATUS(status);
-			pr_debug("test child finished with %d\n", err);
-		} else if (WIFSIGNALED(status)) {
-			err = -1;
-			pr_debug("test child interrupted\n");
-		}
-	}
-
-	return err;
-}
-
-#define for_each_test(j, k, t)			\
-	for (j = 0, k = 0; j < ARRAY_SIZE(tests); j++, k = 0)	\
-		while ((t = tests[j][k++]) != NULL)
-
-static int test_and_print(struct test_suite *t, int subtest)
-{
+	struct child_test *child = container_of(process, struct child_test, process);
 	int err;
 
-	pr_debug("\n--- start ---\n");
-	err = run_test(t, subtest);
-	pr_debug("---- end ----\n");
+	pr_debug("--- start ---\n");
+	pr_debug("test child forked, pid %d\n", getpid());
+	err = test_function(child->test, child->subtest)(child->test, child->subtest);
+	pr_debug("---- end(%d) ----\n", err);
+	fflush(NULL);
+	return -err;
+}
 
-	if (!has_subtests(t))
-		pr_debug("%s:", t->desc);
-	else
-		pr_debug("%s subtest %d:", t->desc, subtest + 1);
+static int print_test_result(struct test_suite *t, int i, int subtest, int result, int width)
+{
+	if (has_subtests(t)) {
+		int subw = width > 2 ? width - 2 : width;
 
-	switch (err) {
+		pr_info("%3d.%1d: %-*s:", i + 1, subtest + 1, subw, test_description(t, subtest));
+	} else
+		pr_info("%3d: %-*s:", i + 1, width, test_description(t, subtest));
+
+	switch (result) {
 	case TEST_OK:
 		pr_info(" Ok\n");
 		break;
···
 		break;
 	}
 
-	return err;
+	return 0;
 }
+
+static int finish_test(struct child_test *child_test, int width)
+{
+	struct test_suite *t = child_test->test;
+	int i = child_test->test_num;
+	int subi = child_test->subtest;
+	int out = child_test->process.out;
+	int err = child_test->process.err;
+	bool out_done = out <= 0;
+	bool err_done = err <= 0;
+	struct strbuf out_output = STRBUF_INIT;
+	struct strbuf err_output = STRBUF_INIT;
+	int ret;
+
+	/*
+	 * For test suites with subtests, display the suite name ahead of the
+	 * sub test names.
+	 */
+	if (has_subtests(t) && subi == 0)
+		pr_info("%3d: %-*s:\n", i + 1, width, test_description(t, -1));
+
+	/*
+	 * Busy loop reading from the child's stdout and stderr that are set to
+	 * be non-blocking until EOF.
+	 */
+	if (!out_done)
+		fcntl(out, F_SETFL, O_NONBLOCK);
+	if (!err_done)
+		fcntl(err, F_SETFL, O_NONBLOCK);
+	if (verbose > 1) {
+		if (has_subtests(t))
+			pr_info("%3d.%1d: %s:\n", i + 1, subi + 1, test_description(t, subi));
+		else
+			pr_info("%3d: %s:\n", i + 1, test_description(t, -1));
+	}
+	while (!out_done || !err_done) {
+		struct pollfd pfds[2] = {
+			{ .fd = out,
+			  .events = POLLIN | POLLERR | POLLHUP | POLLNVAL,
+			},
+			{ .fd = err,
+			  .events = POLLIN | POLLERR | POLLHUP | POLLNVAL,
+			},
+		};
+		char buf[512];
+		ssize_t len;
+
+		/* Poll to avoid excessive spinning, timeout set for 1000ms. */
+		poll(pfds, ARRAY_SIZE(pfds), /*timeout=*/1000);
+		if (!out_done && pfds[0].revents) {
+			errno = 0;
+			len = read(out, buf, sizeof(buf) - 1);
+
+			if (len <= 0) {
+				out_done = errno != EAGAIN;
+			} else {
+				buf[len] = '\0';
+				if (verbose > 1)
+					fprintf(stdout, "%s", buf);
+				else
+					strbuf_addstr(&out_output, buf);
+			}
+		}
+		if (!err_done && pfds[1].revents) {
+			errno = 0;
+			len = read(err, buf, sizeof(buf) - 1);
+
+			if (len <= 0) {
+				err_done = errno != EAGAIN;
+			} else {
+				buf[len] = '\0';
+				if (verbose > 1)
+					fprintf(stdout, "%s", buf);
+				else
+					strbuf_addstr(&err_output, buf);
+			}
+		}
+	}
+	/* Clean up child process. */
+	ret = finish_command(&child_test->process);
+	if (verbose == 1 && ret == TEST_FAIL) {
+		/* Add header for test that was skipped above. */
+		if (has_subtests(t))
+			pr_info("%3d.%1d: %s:\n", i + 1, subi + 1, test_description(t, subi));
+		else
+			pr_info("%3d: %s:\n", i + 1, test_description(t, -1));
+		fprintf(stdout, "%s", out_output.buf);
+		fprintf(stderr, "%s", err_output.buf);
+	}
+	strbuf_release(&out_output);
+	strbuf_release(&err_output);
+	print_test_result(t, i, subi, ret, width);
+	if (out > 0)
+		close(out);
+	if (err > 0)
+		close(err);
+	return 0;
+}
+
+static int start_test(struct test_suite *test, int i, int subi, struct child_test **child,
+		      int width)
+{
+	int err;
+
+	*child = NULL;
+	if (dont_fork) {
+		pr_debug("--- start ---\n");
+		err = test_function(test, subi)(test, subi);
+		pr_debug("---- end ----\n");
+		print_test_result(test, i, subi, err, width);
+		return 0;
+	}
+
+	*child = zalloc(sizeof(**child));
+	if (!*child)
+		return -ENOMEM;
+
+	(*child)->test = test;
+	(*child)->test_num = i;
+	(*child)->subtest = subi;
+	(*child)->process.pid = -1;
+	(*child)->process.no_stdin = 1;
+	if (verbose <= 0) {
+		(*child)->process.no_stdout = 1;
+		(*child)->process.no_stderr = 1;
+	} else {
+		(*child)->process.out = -1;
+		(*child)->process.err = -1;
+	}
+	(*child)->process.no_exec_cmd = run_test_child;
+	err = start_command(&(*child)->process);
+	if (err || parallel)
+		return  err;
+	return finish_test(*child, width);
+}
+
+#define for_each_test(j, k, t)					\
+	for (j = 0, k = 0; j < ARRAY_SIZE(tests); j++, k = 0)	\
+		while ((t = tests[j][k++]) != NULL)
 
 static int __cmd_test(int argc, const char *argv[], struct intlist *skiplist)
 {
···
 	unsigned int j, k;
 	int i = 0;
 	int width = 0;
+	size_t num_tests = 0;
+	struct child_test **child_tests;
+	int child_test_num = 0;
 
 	for_each_test(j, k, t) {
 		int len = strlen(test_description(t, -1));
 
 		if (width < len)
 			width = len;
+
+		if (has_subtests(t)) {
+			for (int subi = 0, subn = num_subtests(t); subi < subn; subi++) {
+				len = strlen(test_description(t, subi));
+				if (width < len)
+					width = len;
+				num_tests++;
+			}
+		} else {
+			num_tests++;
+		}
 	}
+	child_tests = calloc(num_tests, sizeof(*child_tests));
+	if (!child_tests)
+		return -ENOMEM;
 
 	for_each_test(j, k, t) {
 		int curr = i++;
-		int subi;
 
 		if (!perf_test__matches(test_description(t, -1), curr, argc, argv)) {
 			bool skip = true;
-			int subn;
 
-			subn = num_subtests(t);
-
-			for (subi = 0; subi < subn; subi++) {
+			for (int subi = 0, subn = num_subtests(t); subi < subn; subi++) {
 				if (perf_test__matches(test_description(t, subi),
 							curr, argc, argv))
 					skip = false;
···
 				continue;
 		}
 
-		pr_info("%3d: %-*s:", i, width, test_description(t, -1));
-
 		if (intlist__find(skiplist, i)) {
+			pr_info("%3d: %-*s:", curr + 1, width, test_description(t, -1));
 			color_fprintf(stderr, PERF_COLOR_YELLOW, " Skip (user override)\n");
 			continue;
 		}
 
 		if (!has_subtests(t)) {
-			test_and_print(t, -1);
+			int err = start_test(t, curr, -1, &child_tests[child_test_num++], width);
+
+			if (err) {
+				/* TODO: if parallel waitpid the already forked children. */
+				free(child_tests);
+				return err;
+			}
 		} else {
-			int subn = num_subtests(t);
-			/*
-			 * minus 2 to align with normal testcases.
-			 * For subtest we print additional '.x' in number.
-			 * for example:
-			 *
-			 * 35: Test LLVM searching and compiling                        :
-			 * 35.1: Basic BPF llvm compiling test                          : Ok
-			 */
-			int subw = width > 2 ? width - 2 : width;
+			for (int subi = 0, subn = num_subtests(t); subi < subn; subi++) {
+				int err;
 
-			if (subn <= 0) {
-				color_fprintf(stderr, PERF_COLOR_YELLOW,
-					      " Skip (not compiled in)\n");
-				continue;
-			}
-			pr_info("\n");
-
-			for (subi = 0; subi < subn; subi++) {
-				int len = strlen(test_description(t, subi));
-
-				if (subw < len)
-					subw = len;
-			}
-
-			for (subi = 0; subi < subn; subi++) {
 				if (!perf_test__matches(test_description(t, subi),
 							curr, argc, argv))
 					continue;
 
-				pr_info("%3d.%1d: %-*s:", i, subi + 1, subw,
-					test_description(t, subi));
-				test_and_print(t, subi);
+				err = start_test(t, curr, subi, &child_tests[child_test_num++],
+						 width);
+				if (err)
+					return err;
 			}
 		}
 	}
+	for (i = 0; i < child_test_num; i++) {
+		if (parallel) {
+			int ret  = finish_test(child_tests[i], width);
+
+			if (ret)
+				return ret;
+		}
+		free(child_tests[i]);
+	}
+	free(child_tests);
 	return 0;
 }
 
···
 		    "be more verbose (show symbol address, etc)"),
 	OPT_BOOLEAN('F', "dont-fork", &dont_fork,
 		    "Do not fork for testcase"),
+	OPT_BOOLEAN('p', "parallel", &parallel,
+		    "Run the tests altogether in parallel"),
 	OPT_STRING('w', "workload", &workload, "work", "workload to run for testing"),
 	OPT_STRING(0, "dso", &dso_to_test, "dso", "dso to test"),
 	OPT_STRING(0, "objdump", &test_objdump_path, "path",