scx: Add infeasible weights test

Signed-off-by: David Vernet <[email protected]>

tools/testing/selftests/scx/Makefile

@@ -153,6 +153,7 @@ override define CLEAN
 	rm -f *.o *.bpf.o *.bpf.skel.h *.bpf.subskel.h
 	rm -f $(TEST_GEN_PROGS)
 	rm -f runner
+	rm -f highpri
 endef
 
 auto-test-targets :=			\
@@ -193,7 +194,10 @@ runner: $(SCXOBJ_DIR)/runner.o $(BPFOBJ) $(testcase-targets)
 
 TEST_GEN_PROGS := runner
 
-all: runner
+highpri: highpri.c infeasible.sh
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<
+
+all: runner highpri
 
 .PHONY: all clean help
 

tools/testing/selftests/scx/highpri.c

@@ -0,0 +1,106 @@
+#include <errno.h>
+#include <libgen.h>
+#include <pthread.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+
+#define MIN_NICENESS -20
+#define MAX_NICENESS 19
+static int niceness = MIN_NICENESS;
+
+#define MAX_THREADS 1024
+
+static const char help_fmt[] =
+"A helper for creating infeasible weight conditions.\n"
+"\n"
+"Usage: %s [-n NICENESS] [-t NTASKS] [-h]\n"
+"\n"
+"  -n NICENESS   The niceness value to use for each thread. Must be in [-20, 19].\n"
+"  -t NTASKS     The number of tasks to create. Must not exceed 1024.\n"
+"  -h            Display this help and exit\n";
+
+
+static volatile int done = 0;
+
+static void handle_sigint(int sig)
+{
+	done = 1;
+}
+
+static void *busy_spin(void *ctx)
+{
+	uint64_t value = 0;
+	pid_t pid = getpid();
+	pthread_t tid = pthread_self();
+
+	if (!nice(niceness) && errno != 0) {
+		fprintf(stderr, "Failure: (%s)\n", strerror(errno));
+		done = 1;
+		return NULL;
+	}
+
+	while (!done) {
+		value++;
+		if (value % 10000 == 0) {
+			printf("%d[%lu] nice= %d\n",
+			       pid, tid, nice(0));
+		}
+	}
+
+	return NULL;
+}
+
+int main(int argc, char **argv)
+{
+	unsigned num_threads = 1, i;
+	pthread_t tids[MAX_THREADS];
+	int opt;
+
+	signal(SIGINT, handle_sigint);
+	signal(SIGTERM, handle_sigint);
+
+	while ((opt = getopt(argc, argv, "n:t:h")) != -1) {
+		switch (opt) {
+		case 'n':
+			niceness = strtol(optarg, NULL, 10);
+			break;
+		case 't':
+			num_threads = strtol(optarg, NULL, 10);
+			break;
+		default:
+			fprintf(stderr, help_fmt, basename(argv[0]));
+			return opt != 'h';
+		}
+	}
+
+	if (niceness < MIN_NICENESS || niceness > MAX_NICENESS) {
+		fprintf(stderr, "Invalid niceness %d, must be in [%d, %d]\n",
+			niceness, MIN_NICENESS, MAX_NICENESS);
+		fprintf(stderr, help_fmt, basename(argv[0]));
+		return 1;
+	}
+
+	if (num_threads >= MAX_THREADS) {
+		fprintf(stderr, "%u exceeds max threads %u\n", num_threads,
+			MAX_THREADS);
+		fprintf(stderr, help_fmt, basename(argv[0]));
+		return 1;
+	}
+
+	for (i = 0; i < num_threads; i++) {
+		if (pthread_create(&tids[i], NULL, busy_spin, NULL)) {
+			fprintf(stderr, "Failed to create thread %u\n", i);
+			return 1;
+		}
+	}
+
+	for (i = 0; i < num_threads; i++)
+		pthread_join(tids[i], NULL);
+
+	return 0;
+}

tools/testing/selftests/scx/infeasible.sh

@@ -0,0 +1,99 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2024 David Vernet <[email protected]>
+# Copyright (C) 2024 Meta Platforms, Inc. and affiliates.
+
+# Script to make a cgroup with conditions that should cause the infeasible
+# weight problem to manifest
+
+INFEASIBLE_CGRP_ROOT="/sys/fs/cgroup/infeasible.scope"
+
+function cgrp_n_tasks() {
+	return "${curr_pids}"
+}
+
+# create_cgrp() - Create the root infeasible cgroup
+function create_cgrp() {
+	local weight=10000
+
+	if [[ ! -d "${INFEASIBLE_CGRP_ROOT}" ]]; then
+		mkdir "${INFEASIBLE_CGRP_ROOT}"
+		echo "created root infeasible group ${INFEASIBLE_CGRP_ROOT}"
+	else
+		echo "root infeasible group ${INFEASIBLE_CGRP_ROOT} already existed"
+		local curr_pids=$(cat "${INFEASIBLE_CGRP_ROOT}/pids.current")
+		if  [ "${curr_pids}" != "0" ]; then
+			echo "ERR: tasks found in  ${INFEASIBLE_CGRP_ROOT}"
+			exit 1
+		fi
+	fi
+
+	echo "setting ${INFEASIBLE_CGRP_ROOT} weight to ${weight}"
+	echo ${weight} > "${INFEASIBLE_CGRP_ROOT}/cpu.weight"
+	echo "set ${INFEASIBLE_CGRP_ROOT} weight to ${weight}"
+}
+
+# spawn_tasks(ntasks) - Spawn tasks with low niceness and return the pid
+function spawn_tasks() {
+	local ntasks=$1
+
+	if [ -z $ntasks ]; then
+		ntasks=$(($(nproc)/4))
+	fi
+	echo "spawning ${ntasks} tasks"
+	./highpri -t ${ntasks} > /tmp/highpri.out 2> /tmp/highpri.err &
+	local status=$?
+	echo "status was: ${status}"
+	pid=$!
+	echo "pid is ${pid}"
+	echo "spawned highpri task ${pid}"
+	if [ ${pid} -le 0 ]; then
+		echo "ERR: failed to spawned highpri tasks"
+		exit 1
+	fi
+}
+
+# Move the tasks into the infeasible cgroup
+function move_into_cgrp() {
+	local pid=$1
+	local procsfile="${INFEASIBLE_CGRP_ROOT}/cgroup.procs"
+	local pidsfile="${INFEASIBLE_CGRP_ROOT}/pids.current"
+
+	echo "moving ${pid} into ${procsfile}"
+	echo "	procs in before: $(cat ${pidsfile})"
+	echo "${pid}" >> "${procsfile}"
+	local status=$?
+	echo "status was: ${status}"
+	if [ ${status} -ne 0 ]; then
+		echo "ERR: failed to move ${pid} into ${procsfile}"
+		echo "ERR: destroying ${pid}"
+		kill -9 ${pid}
+		echo "ERR: killed ${pid}. waiting for exit..."
+		wait
+		echo "ERR: ${pid} exited"
+		exit 1
+	fi
+	echo "	procs in after: $(cat ${pidsfile})"
+}
+
+function cleanup() {
+	local curr_pids=$(cat "${INFEASIBLE_CGRP_ROOT}/pids.current")
+	if  [ "${curr_pids}" != "0" ]; then
+		echo "WARN: ${curr_pids} tasks remaining in  ${INFEASIBLE_CGRP_ROOT}"
+	fi
+}
+
+function _term() {
+	echo "Caught SIGINT signal"
+	kill -s SIGINT "${pid}"
+}
+
+create_cgrp
+pid=""
+trap _term SIGINT
+spawn_tasks
+move_into_cgrp ${pid}
+echo "success: waiting for ${pid} to finish"
+wait ${pid}
+echo "${pid} exited. cleaning up..."
+cleanup