proc_softirqs.c

// SPDX-License-Identifier: GPL-3.0-or-later

#include "plugin_proc.h"

#define PLUGIN_PROC_MODULE_SOFTIRQS_NAME "/proc/softirqs"

#define MAX_INTERRUPT_NAME 50

struct cpu_interrupt {
    unsigned long long value;
    RRDDIM *rd;
};

struct interrupt {
    int used;
    char *id;
    char name[MAX_INTERRUPT_NAME + 1];
    RRDDIM *rd;
    unsigned long long total;
    struct cpu_interrupt cpu[];
};

// since each interrupt is variable in size
// we use this to calculate its record size
#define recordsize(cpus) (sizeof(struct interrupt) + ((cpus) * sizeof(struct cpu_interrupt)))

// given a base, get a pointer to each record
#define irrindex(base, line, cpus) ((struct interrupt *)&((char *)(base))[(line) * recordsize(cpus)])

static inline struct interrupt *get_interrupts_array(size_t lines, int cpus) {
    static struct interrupt *irrs = NULL;
    static size_t allocated = 0;

    if(unlikely(lines != allocated)) {
        uint32_t l;
        int c;

        irrs = (struct interrupt *)reallocz(irrs, lines * recordsize(cpus));

        // reset all interrupt RRDDIM pointers as any line could have shifted
        for(l = 0; l < lines ;l++) {
            struct interrupt *irr = irrindex(irrs, l, cpus);
            irr->rd = NULL;
            irr->name[0] = '\0';
            for(c = 0; c < cpus ;c++)
                irr->cpu[c].rd = NULL;
        }

        allocated = lines;
    }

    return irrs;
}

int do_proc_softirqs(int update_every, usec_t dt) {
    (void)dt;
    static procfile *ff = NULL;
    static int cpus = -1, do_per_core = CONFIG_BOOLEAN_INVALID;
    struct interrupt *irrs = NULL;

    if(unlikely(do_per_core == CONFIG_BOOLEAN_INVALID))
        do_per_core = config_get_boolean_ondemand("plugin:proc:/proc/softirqs", "interrupts per core", CONFIG_BOOLEAN_AUTO);

    if(unlikely(!ff)) {
        char filename[FILENAME_MAX + 1];
        snprintfz(filename, FILENAME_MAX, "%s%s", netdata_configured_host_prefix, "/proc/softirqs");
        ff = procfile_open(config_get("plugin:proc:/proc/softirqs", "filename to monitor", filename), " \t:", PROCFILE_FLAG_DEFAULT);
        if(unlikely(!ff)) return 1;
    }

    ff = procfile_readall(ff);
    if(unlikely(!ff)) return 0; // we return 0, so that we will retry to open it next time

    size_t lines = procfile_lines(ff), l;
    size_t words = procfile_linewords(ff, 0);

    if(unlikely(!lines)) {
        error("Cannot read /proc/softirqs, zero lines reported.");
        return 1;
    }

    // find how many CPUs are there
    if(unlikely(cpus == -1)) {
        uint32_t w;
        cpus = 0;
        for(w = 0; w < words ; w++) {
            if(likely(strncmp(procfile_lineword(ff, 0, w), "CPU", 3) == 0))
                cpus++;
        }
    }

    if(unlikely(!cpus)) {
        error("PLUGIN: PROC_SOFTIRQS: Cannot find the number of CPUs in /proc/softirqs");
        return 1;
    }

    // allocate the size we need;
    irrs = get_interrupts_array(lines, cpus);
    irrs[0].used = 0;

    // loop through all lines
    for(l = 1; l < lines ;l++) {
        struct interrupt *irr = irrindex(irrs, l, cpus);
        irr->used = 0;
        irr->total = 0;

        words = procfile_linewords(ff, l);
        if(unlikely(!words)) continue;

        irr->id = procfile_lineword(ff, l, 0);
        if(unlikely(!irr->id || !irr->id[0])) continue;

        int c;
        for(c = 0; c < cpus ;c++) {
            if(likely((c + 1) < (int)words))
                irr->cpu[c].value = str2ull(procfile_lineword(ff, l, (uint32_t)(c + 1)));
            else
                irr->cpu[c].value = 0;

            irr->total += irr->cpu[c].value;
        }

        strncpyz(irr->name, irr->id, MAX_INTERRUPT_NAME);

        irr->used = 1;
    }

    // --------------------------------------------------------------------

    static RRDSET *st_system_softirqs = NULL;
    if(unlikely(!st_system_softirqs))
        st_system_softirqs = rrdset_create_localhost(
                "system"
                , "softirqs"
                , NULL
                , "softirqs"
                , NULL
                , "System softirqs"
                , "softirqs/s"
                , PLUGIN_PROC_NAME
                , PLUGIN_PROC_MODULE_SOFTIRQS_NAME
                , NETDATA_CHART_PRIO_SYSTEM_SOFTIRQS
                , update_every
                , RRDSET_TYPE_STACKED
        );
    else
        rrdset_next(st_system_softirqs);

    for(l = 0; l < lines ;l++) {
        struct interrupt *irr = irrindex(irrs, l, cpus);

        if(irr->used && irr->total) {
            // some interrupt may have changed without changing the total number of lines
            // if the same number of interrupts have been added and removed between two
            // calls of this function.
            if(unlikely(!irr->rd || strncmp(irr->name, irr->rd->name, MAX_INTERRUPT_NAME) != 0)) {
                irr->rd = rrddim_add(st_system_softirqs, irr->id, irr->name, 1, 1, RRD_ALGORITHM_INCREMENTAL);
                rrddim_set_name(st_system_softirqs, irr->rd, irr->name);

                // also reset per cpu RRDDIMs to avoid repeating strncmp() in the per core loop
                if(likely(do_per_core != CONFIG_BOOLEAN_NO)) {
                    int c;
                    for(c = 0; c < cpus; c++) irr->cpu[c].rd = NULL;
                }
            }

            rrddim_set_by_pointer(st_system_softirqs, irr->rd, irr->total);
        }
    }

    rrdset_done(st_system_softirqs);

    // --------------------------------------------------------------------

    if(do_per_core != CONFIG_BOOLEAN_NO) {
        static RRDSET **core_st = NULL;
        static int old_cpus = 0;

        if(old_cpus < cpus) {
            core_st = reallocz(core_st, sizeof(RRDSET *) * cpus);
            memset(&core_st[old_cpus], 0, sizeof(RRDSET *) * (cpus - old_cpus));
            old_cpus = cpus;
        }

        int c;

        for(c = 0; c < cpus ; c++) {
            if(unlikely(!core_st[c])) {
                // find if everything is just zero
                unsigned long long core_sum = 0;

                for (l = 0; l < lines; l++) {
                    struct interrupt *irr = irrindex(irrs, l, cpus);
                    if (unlikely(!irr->used)) continue;
                    core_sum += irr->cpu[c].value;
                }

                if (unlikely(core_sum == 0)) continue; // try next core

                char id[50 + 1];
                snprintfz(id, 50, "cpu%d_softirqs", c);

                char title[100 + 1];
                snprintfz(title, 100, "CPU%d softirqs", c);

                core_st[c] = rrdset_create_localhost(
                        "cpu"
                        , id
                        , NULL
                        , "softirqs"
                        , "cpu.softirqs"
                        , title
                        , "softirqs/s"
                        , PLUGIN_PROC_NAME
                        , PLUGIN_PROC_MODULE_SOFTIRQS_NAME
                        , NETDATA_CHART_PRIO_SOFTIRQS_PER_CORE + c
                        , update_every
                        , RRDSET_TYPE_STACKED
                );
            }
            else
                rrdset_next(core_st[c]);

            for(l = 0; l < lines ;l++) {
                struct interrupt *irr = irrindex(irrs, l, cpus);

                if(irr->used && (do_per_core == CONFIG_BOOLEAN_YES || irr->cpu[c].value)) {
                    if(unlikely(!irr->cpu[c].rd)) {
                        irr->cpu[c].rd = rrddim_add(core_st[c], irr->id, irr->name, 1, 1, RRD_ALGORITHM_INCREMENTAL);
                        rrddim_set_name(core_st[c], irr->cpu[c].rd, irr->name);
                    }

                    rrddim_set_by_pointer(core_st[c], irr->cpu[c].rd, irr->cpu[c].value);
                }
            }

            rrdset_done(core_st[c]);
        }
    }

    return 0;
}