1/* SPDX-License-Identifier: GPL-2.0 */
  2/*
  3 * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
  4 * Copyright (c) 2022 Tejun Heo <tj@kernel.org>
  5 * Copyright (c) 2022 David Vernet <dvernet@meta.com>
  6 */
  7#define _GNU_SOURCE
  8#include <sched.h>
  9#include <stdio.h>
 10#include <unistd.h>
 11#include <inttypes.h>
 12#include <signal.h>
 13#include <libgen.h>
 14#include <bpf/bpf.h>
 15#include <scx/common.h>
 16#include "scx_central.bpf.skel.h"
 17
 18const char help_fmt[] =
 19"A central FIFO sched_ext scheduler.\n"
 20"\n"
 21"See the top-level comment in .bpf.c for more details.\n"
 22"\n"
 23"Usage: %s [-s SLICE_US] [-c CPU]\n"
 24"\n"
 25"  -s SLICE_US   Override slice duration\n"
 26"  -c CPU        Override the central CPU (default: 0)\n"
 27"  -v            Print libbpf debug messages\n"
 28"  -h            Display this help and exit\n";
 29
 30static bool verbose;
 31static volatile int exit_req;
 32
 33static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
 34{
 35	if (level == LIBBPF_DEBUG && !verbose)
 36		return 0;
 37	return vfprintf(stderr, format, args);
 38}
 39
 40static void sigint_handler(int dummy)
 41{
 42	exit_req = 1;
 43}
 44
 45int main(int argc, char **argv)
 46{
 47	struct scx_central *skel;
 48	struct bpf_link *link;
 49	__u64 seq = 0, ecode;
 50	__s32 opt;
 51	cpu_set_t *cpuset;
 52
 53	libbpf_set_print(libbpf_print_fn);
 54	signal(SIGINT, sigint_handler);
 55	signal(SIGTERM, sigint_handler);
 56restart:
 57	skel = SCX_OPS_OPEN(central_ops, scx_central);
 58
 59	skel->rodata->central_cpu = 0;
 60	skel->rodata->nr_cpu_ids = libbpf_num_possible_cpus();
 61
 62	while ((opt = getopt(argc, argv, "s:c:pvh")) != -1) {
 63		switch (opt) {
 64		case 's':
 65			skel->rodata->slice_ns = strtoull(optarg, NULL, 0) * 1000;
 66			break;
 67		case 'c':
 68			skel->rodata->central_cpu = strtoul(optarg, NULL, 0);
 69			break;
 70		case 'v':
 71			verbose = true;
 72			break;
 73		default:
 74			fprintf(stderr, help_fmt, basename(argv[0]));
 75			return opt != 'h';
 76		}
 77	}
 78
 79	/* Resize arrays so their element count is equal to cpu count. */
 80	RESIZE_ARRAY(skel, data, cpu_gimme_task, skel->rodata->nr_cpu_ids);
 81	RESIZE_ARRAY(skel, data, cpu_started_at, skel->rodata->nr_cpu_ids);
 82
 83	SCX_OPS_LOAD(skel, central_ops, scx_central, uei);
 84
 85	/*
 86	 * Affinitize the loading thread to the central CPU, as:
 87	 * - That's where the BPF timer is first invoked in the BPF program.
 88	 * - We probably don't want this user space component to take up a core
 89	 *   from a task that would benefit from avoiding preemption on one of
 90	 *   the tickless cores.
 91	 *
 92	 * Until BPF supports pinning the timer, it's not guaranteed that it
 93	 * will always be invoked on the central CPU. In practice, this
 94	 * suffices the majority of the time.
 95	 */
 96	cpuset = CPU_ALLOC(skel->rodata->nr_cpu_ids);
 97	SCX_BUG_ON(!cpuset, "Failed to allocate cpuset");
 98	CPU_ZERO(cpuset);
 99	CPU_SET(skel->rodata->central_cpu, cpuset);
100	SCX_BUG_ON(sched_setaffinity(0, sizeof(*cpuset), cpuset),
101		   "Failed to affinitize to central CPU %d (max %d)",
102		   skel->rodata->central_cpu, skel->rodata->nr_cpu_ids - 1);
103	CPU_FREE(cpuset);
104
105	link = SCX_OPS_ATTACH(skel, central_ops, scx_central);
106
107	if (!skel->data->timer_pinned)
108		printf("WARNING : BPF_F_TIMER_CPU_PIN not available, timer not pinned to central\n");
109
110	while (!exit_req && !UEI_EXITED(skel, uei)) {
111		printf("[SEQ %llu]\n", seq++);
112		printf("total   :%10" PRIu64 "    local:%10" PRIu64 "   queued:%10" PRIu64 "  lost:%10" PRIu64 "\n",
113		       skel->bss->nr_total,
114		       skel->bss->nr_locals,
115		       skel->bss->nr_queued,
116		       skel->bss->nr_lost_pids);
117		printf("timer   :%10" PRIu64 " dispatch:%10" PRIu64 " mismatch:%10" PRIu64 " retry:%10" PRIu64 "\n",
118		       skel->bss->nr_timers,
119		       skel->bss->nr_dispatches,
120		       skel->bss->nr_mismatches,
121		       skel->bss->nr_retries);
122		printf("overflow:%10" PRIu64 "\n",
123		       skel->bss->nr_overflows);
124		fflush(stdout);
125		sleep(1);
126	}
127
128	bpf_link__destroy(link);
129	ecode = UEI_REPORT(skel, uei);
130	scx_central__destroy(skel);
131
132	if (UEI_ECODE_RESTART(ecode))
133		goto restart;
134	return 0;
135}