runqlat.c

// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
// Copyright (c) 2020 Wenbo Zhang
//
// Based on runqlat(8) from BCC by Bredan Gregg.
// 10-Aug-2020   Wenbo Zhang   Created this.
// #include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <stdbool.h>
#include <fcntl.h>
#include "runqlat.h"
#include "runqlat.skel.h"
#include "trace_helpers.h"

struct env {
    time_t interval;
    pid_t pid;
    int times;
    bool milliseconds;
    bool per_process;
    bool per_thread;
    bool per_pidns;
    bool timestamp;
    bool verbose;
    char* cgroupspath;
    bool cg;
} env = {
    .interval = 1,
    .times = 99999999,
};

static volatile bool exiting;

const char* argp_program_version = "runqlat 0.1";
const char* argp_program_bug_address =
    "https://github.com/iovisor/bcc/tree/master/libbpf-tools";
const char argp_program_doc[] =
    "Summarize run queue (scheduler) latency as a histogram.\n"
    "\n"
    "USAGE: runqlat [--help] [-T] [-m] [--pidnss] [-L] [-P] [-p PID] "
    "[interval] [count] [-c CG]\n"
    "\n"
    "EXAMPLES:\n"
    "    runqlat         # summarize run queue latency as a histogram\n"
    "    runqlat 1 10    # print 1 second summaries, 10 times\n"
    "    runqlat -P      # show each PID separately\n"
    "    runqlat -p 185  # trace PID 185 only\n"
    "    runqlat -c CG   # Trace process under cgroupsPath CG\n";

#define OPT_PIDNSS 1 /* --pidnss */

static void print_usage(void) {
    printf("%s\n", argp_program_version);
    printf("%s\n", argp_program_doc);
}

static void sig_handler(int sig) {
    exiting = true;
}

static int print_log2_hists(struct bpf_map* hists) {
    const char* units = env.milliseconds ? "msecs" : "usecs";
    int err, fd = bpf_map__fd(hists);
    uint32_t lookup_key = -2, next_key;
    struct hist hist;

    while (!bpf_map_get_next_key(fd, &lookup_key, &next_key)) {
        err = bpf_map_lookup_elem(fd, &next_key, &hist);
        if (err < 0) {
            fprintf(stderr, "failed to lookup hist: %d\n", err);
            return -1;
        }
        if (env.per_process)
            printf("\npid = %d %s\n", next_key, hist.comm);
        else if (env.per_thread)
            printf("\ntid = %d %s\n", next_key, hist.comm);
        else if (env.per_pidns)
            printf("\npidns = %u %s\n", next_key, hist.comm);
        print_log2_hist(hist.slots, MAX_SLOTS, units);
        lookup_key = next_key;
    }

    lookup_key = -2;
    while (!bpf_map_get_next_key(fd, &lookup_key, &next_key)) {
        err = bpf_map_delete_elem(fd, &next_key);
        if (err < 0) {
            fprintf(stderr, "failed to cleanup hist : %d\n", err);
            return -1;
        }
        lookup_key = next_key;
    }
    return 0;
}

int main(int argc, char** argv) {
    struct runqlat_bpf* obj;
    struct tm* tm;
    char ts[32];
    time_t t;
    int err;
    int idx, cg_map_fd;
    int cgfd = -1;

    // parse the args manually for demo purpose
    if (argc > 3 || strcmp(argv[1], "-h") == 0 ||
        strcmp(argv[1], "--help") == 0) {
        print_usage();
        return 0;
    } else if (argc == 2 && strcmp(argv[1], "-P")) {
        env.per_process = true;
    } else if (argc == 3) {
        env.interval = atoi(argv[1]);
        env.times = atoi(argv[2]);
    } else if (argc == 2) {
        env.interval = atoi(argv[1]);
    }
    if ((env.per_thread && (env.per_process || env.per_pidns)) ||
        (env.per_process && env.per_pidns)) {
        fprintf(stderr, "pidnss, pids, tids cann't be used together.\n");
        return 1;
    }
    if (!env.interval) {
        env.interval = 1;
    }

    obj = runqlat_bpf__open();
    if (!obj) {
        fprintf(stderr, "failed to open BPF object\n");
        return 1;
    }

    /* initialize global data (filtering options) */
    obj->rodata->targ_per_process = env.per_process;
    obj->rodata->targ_per_thread = env.per_thread;
    obj->rodata->targ_per_pidns = env.per_pidns;
    obj->rodata->targ_ms = env.milliseconds;
    obj->rodata->targ_tgid = env.pid;
    obj->rodata->filter_cg = env.cg;

    err = runqlat_bpf__load(obj);
    if (err) {
        fprintf(stderr, "failed to load BPF object: %d\n", err);
        goto cleanup;
    }

    /* update cgroup path fd to map */
    if (env.cg) {
        idx = 0;
        cg_map_fd = bpf_map__fd(obj->maps.cgroup_map);
        cgfd = open(env.cgroupspath, O_RDONLY);
        if (cgfd < 0) {
            fprintf(stderr, "Failed opening Cgroup path: %s", env.cgroupspath);
            goto cleanup;
        }
        if (bpf_map_update_elem(cg_map_fd, &idx, &cgfd, BPF_ANY)) {
            fprintf(stderr, "Failed adding target cgroup to map");
            goto cleanup;
        }
    }

    err = runqlat_bpf__attach(obj);
    if (err) {
        fprintf(stderr, "failed to attach BPF programs\n");
        goto cleanup;
    }

    printf("Tracing run queue latency... Hit Ctrl-C to end.\n");

    /* main: poll */
    while (1) {
        sleep(env.interval);
        printf("\n");

        if (env.timestamp) {
            time(&t);
            tm = localtime(&t);
            strftime(ts, sizeof(ts), "%H:%M:%S", tm);
            printf("%-8s\n", ts);
        }

        err = print_log2_hists(obj->maps.hists);
        if (err)
            break;

        if (exiting || --env.times == 0)
            break;
    }

cleanup:
    runqlat_bpf__destroy(obj);
    if (cgfd > 0)
        close(cgfd);

    return err != 0;
}