/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
 * Copyright (c) 2022 Tejun Heo <tj@kernel.org>
 * Copyright (c) 2022 David Vernet <dvernet@meta.com>
 */
#define _GNU_SOURCE
#include <sched.h>
#include <stdio.h>
#include <unistd.h>
#include <inttypes.h>
#include <signal.h>
#include <assert.h>
#include <libgen.h>
#include <bpf/bpf.h>
#include <scx/common.h>
#include "scx_central.bpf.skel.h"

const char help_fmt[] =
"A central FIFO sched_ext scheduler.\n"
"\n"
"See the top-level comment in .bpf.c for more details.\n"
"\n"
"Usage: %s [-s SLICE_US] [-c CPU]\n"
"\n"
"  -s SLICE_US   Override slice duration\n"
"  -c CPU        Override the central CPU (default: 0)\n"
"  -v            Print libbpf debug messages\n"
"  -h            Display this help and exit\n";

static bool verbose;
static volatile int exit_req;

static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
{
        if (level == LIBBPF_DEBUG && !verbose)
                return 0;
        return vfprintf(stderr, format, args);
}

static void sigint_handler(int dummy)
{
        exit_req = 1;
}

int main(int argc, char **argv)
{
        struct scx_central *skel;
        struct bpf_link *link;
        __u64 seq = 0, ecode;
        __s32 opt;
        cpu_set_t *cpuset;
        size_t cpuset_size;

        libbpf_set_print(libbpf_print_fn);
        signal(SIGINT, sigint_handler);
        signal(SIGTERM, sigint_handler);
restart:
        optind = 1;
        skel = SCX_OPS_OPEN(central_ops, scx_central);

        skel->rodata->central_cpu = 0;
        skel->rodata->nr_cpu_ids = libbpf_num_possible_cpus();
        skel->rodata->slice_ns = __COMPAT_ENUM_OR_ZERO("scx_public_consts", "SCX_SLICE_DFL");

        assert(skel->rodata->nr_cpu_ids > 0);
        assert(skel->rodata->nr_cpu_ids <= INT32_MAX);

        while ((opt = getopt(argc, argv, "s:c:vh")) != -1) {
                switch (opt) {
                case 's':
                        skel->rodata->slice_ns = strtoull(optarg, NULL, 0) * 1000;
                        break;
                case 'c': {
                        u32 central_cpu = strtoul(optarg, NULL, 0);
                        if (central_cpu >= skel->rodata->nr_cpu_ids) {
                                fprintf(stderr, "invalid central CPU id value, %u given (%u max)\n", central_cpu, skel->rodata->nr_cpu_ids);
                                scx_central__destroy(skel);
                                return -1;
                        }
                        skel->rodata->central_cpu = (s32)central_cpu;
                        break;
                }
                case 'v':
                        verbose = true;
                        break;
                default:
                        fprintf(stderr, help_fmt, basename(argv[0]));
                        return opt != 'h';
                }
        }

        /* Resize arrays so their element count is equal to cpu count. */
        RESIZE_ARRAY(skel, data, cpu_gimme_task, skel->rodata->nr_cpu_ids);
        RESIZE_ARRAY(skel, data, cpu_started_at, skel->rodata->nr_cpu_ids);

        SCX_OPS_LOAD(skel, central_ops, scx_central, uei);

        /*
         * Affinitize the loading thread to the central CPU, as:
         * - That's where the BPF timer is first invoked in the BPF program.
         * - We probably don't want this user space component to take up a core
         *   from a task that would benefit from avoiding preemption on one of
         *   the tickless cores.
         *
         * Until BPF supports pinning the timer, it's not guaranteed that it
         * will always be invoked on the central CPU. In practice, this
         * suffices the majority of the time.
         */
        cpuset = CPU_ALLOC(skel->rodata->nr_cpu_ids);
        SCX_BUG_ON(!cpuset, "Failed to allocate cpuset");
        cpuset_size = CPU_ALLOC_SIZE(skel->rodata->nr_cpu_ids);
        CPU_ZERO_S(cpuset_size, cpuset);
        CPU_SET_S(skel->rodata->central_cpu, cpuset_size, cpuset);
        SCX_BUG_ON(sched_setaffinity(0, cpuset_size, cpuset),
                   "Failed to affinitize to central CPU %d (max %d)",
                   skel->rodata->central_cpu, skel->rodata->nr_cpu_ids - 1);
        CPU_FREE(cpuset);

        link = SCX_OPS_ATTACH(skel, central_ops, scx_central);

        if (!skel->data->timer_pinned)
                printf("WARNING : BPF_F_TIMER_CPU_PIN not available, timer not pinned to central\n");

        while (!exit_req && !UEI_EXITED(skel, uei)) {
                printf("[SEQ %llu]\n", seq++);
                printf("total   :%10" PRIu64 "    local:%10" PRIu64 "   queued:%10" PRIu64 "  lost:%10" PRIu64 "\n",
                       skel->bss->nr_total,
                       skel->bss->nr_locals,
                       skel->bss->nr_queued,
                       skel->bss->nr_lost_pids);
                printf("timer   :%10" PRIu64 " dispatch:%10" PRIu64 " mismatch:%10" PRIu64 " retry:%10" PRIu64 "\n",
                       skel->bss->nr_timers,
                       skel->bss->nr_dispatches,
                       skel->bss->nr_mismatches,
                       skel->bss->nr_retries);
                printf("overflow:%10" PRIu64 "\n",
                       skel->bss->nr_overflows);
                fflush(stdout);
                sleep(1);
        }

        bpf_link__destroy(link);
        ecode = UEI_REPORT(skel, uei);
        scx_central__destroy(skel);

        if (UEI_ECODE_RESTART(ecode))
                goto restart;
        return 0;
}