#!/usr/bin/env bpftrace
// SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
//
// On-CPU time distribution per thread.
// Shows how long threads run before being preempted or yielding.
//
// Usage: sudo bpftrace cpudist.bt

tracepoint:sched:sched_switch
{
    // Record when new thread starts running
    @start[args.next_pid] = nsecs;

    // Calculate how long prev thread was on-CPU
    $prev_start = @start[args.prev_pid];
    if ($prev_start) {
        @usecs[comm] = hist((nsecs - $prev_start) / 1000);
        delete(@start[args.prev_pid]);
    }
}

interval:s:10
{
    printf("\n--- On-CPU Time Distribution (us) by thread ---\n");
    print(@usecs);
    clear(@usecs);
}

END
{
    clear(@start);
}