drivers/gator/gator_events_sched.c

/**
 * Copyright (C) Arm Limited 2010-2016. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include "gator.h"
#include <trace/events/sched.h>

#define SCHED_SWITCH    0
#define SCHED_TOTAL     (SCHED_SWITCH+1)

static ulong sched_switch_enabled[GATOR_CLUSTER_COUNT];
static bool sched_switch_enabled_any;
static ulong sched_switch_key[GATOR_CLUSTER_COUNT];
static DEFINE_PER_CPU(int[SCHED_TOTAL], schedCnt);
static DEFINE_PER_CPU(int[SCHED_TOTAL * 2], schedGet);

#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 4, 0)
GATOR_DEFINE_PROBE(sched_switch, TP_PROTO(struct task_struct *prev, struct task_struct *next))
#else
GATOR_DEFINE_PROBE(sched_switch, TP_PROTO(bool preempt, struct task_struct *prev, struct task_struct *next))
#endif
{
    unsigned long flags;

    /* disable interrupts to synchronize with gator_events_sched_read()
     * spinlocks not needed since percpu buffers are used
     */
    local_irq_save(flags);
    per_cpu(schedCnt, get_physical_cpu())[SCHED_SWITCH]++;
    local_irq_restore(flags);
}

static int gator_events_sched_create_files(struct super_block *sb, struct dentry *root)
{
    struct dentry *dir;
    int i;
    char buf[40];

    /* switch */
    for (i = 0; i < gator_cluster_count; i++) {
        snprintf(buf, sizeof(buf), "%s_switch", gator_clusters[i]->pmnc_name);
        dir = gatorfs_mkdir(sb, root, buf);
        if (!dir)
            return -1;
        gatorfs_create_ulong(sb, dir, "enabled", &sched_switch_enabled[i]);
        gatorfs_create_ro_ulong(sb, dir, "key", &sched_switch_key[i]);
    }

    return 0;
}

static int gator_events_sched_start(void)
{
    int i;

    sched_switch_enabled_any = false;
    for (i = 0; i < gator_cluster_count; i++) {
        if (sched_switch_enabled[i]) {
            sched_switch_enabled_any = true;
            break;
        }
    }

    /* register tracepoints */
    if (sched_switch_enabled_any)
        if (GATOR_REGISTER_TRACE(sched_switch))
            goto sched_switch_exit;
    pr_debug("gator: registered scheduler event tracepoints\n");

    return 0;

    /* unregister tracepoints on error */
sched_switch_exit:
    pr_err("gator: scheduler event tracepoints failed to activate, please verify that tracepoints are enabled in the linux kernel\n");

    return -1;
}

static void gator_events_sched_stop(void)
{
    if (sched_switch_enabled_any)
        GATOR_UNREGISTER_TRACE(sched_switch);
    pr_debug("gator: unregistered scheduler event tracepoints\n");

    sched_switch_enabled_any = false;
    memset(sched_switch_enabled, 0, sizeof(sched_switch_enabled));
}

static int gator_events_sched_read(int **buffer, bool sched_switch)
{
    unsigned long flags;
    int len, value;
    int cpu = get_physical_cpu();
    int cluster = gator_clusterids[cpu];

    len = 0;
    if (sched_switch_enabled[cluster]) {
        local_irq_save(flags);
        value = per_cpu(schedCnt, cpu)[SCHED_SWITCH];
        per_cpu(schedCnt, cpu)[SCHED_SWITCH] = 0;
        local_irq_restore(flags);
        per_cpu(schedGet, cpu)[len++] = sched_switch_key[cluster];
        per_cpu(schedGet, cpu)[len++] = value;
    }

    if (buffer)
        *buffer = per_cpu(schedGet, cpu);

    return len;
}

static struct gator_interface gator_events_sched_interface = {
    .name = "sched",
    .create_files = gator_events_sched_create_files,
    .start = gator_events_sched_start,
    .stop = gator_events_sched_stop,
    .read = gator_events_sched_read,
};

int gator_events_sched_init(void)
{
    int i;

    for (i = 0; i < gator_cluster_count; i++) {
        sched_switch_enabled[i] = 0;
        sched_switch_key[i] = gator_events_get_key();
    }

    return gator_events_install(&gator_events_sched_interface);
}