funclatency.bt

#!/usr/bin/env bpftrace
// SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
//
// Latency of specific functions (requires debug symbols / profiling build).
// Measures function entry-to-exit time.
//
// Usage:
//   # Trace a specific function by name (requires DWARF symbols):
//   sudo bpftrace -p <PID> -e '
//     uprobe:/path/to/binary:function_name { @start[tid] = nsecs; }
//     uretprobe:/path/to/binary:function_name /@start[tid]/ {
//       @latency_us = hist((nsecs - @start[tid]) / 1000);
//       delete(@start[tid]);
//     }'
//
//   # Or use this script with BINARY and FUNC env vars:
//   sudo BINARY=/path/to/binary FUNC=function_name bpftrace funclatency.bt
//
// Build target with symbols:
//   cargo build --profile profiling --features nvtx

BEGIN
{
    printf("Tracing function latency... Hit Ctrl-C to end.\n");
    printf("Note: Set BINARY and FUNC environment variables, or edit this script.\n");
    printf("Example: sudo BINARY=target/profiling/dynamo-frontend FUNC=apply_template bpftrace funclatency.bt\n");
}

// Generic uprobe placeholder — edit the probe target as needed.
// bpftrace doesn't support env var substitution in probe specs,
// so this serves as a template. Use the one-liner above for actual tracing.

// Example for tokenizer:
// uprobe:target/profiling/dynamo-frontend:*gather_tokens* { @start[tid] = nsecs; }
// uretprobe:target/profiling/dynamo-frontend:*gather_tokens* /@start[tid]/ {
//   @latency_us["gather_tokens"] = hist((nsecs - @start[tid]) / 1000);
//   delete(@start[tid]);
// }

interval:s:1
{
    printf(".");
}

END
{
    printf("\nDone.\n");
}