1 files changed, 107 insertions, 0 deletions
diff --git a/contrib/tracing/log_utxocache_flush.py b/contrib/tracing/log_utxocache_flush.py
new file mode 100755
index 0000000000..df27dc193a
--- /dev/null
+++ b/contrib/tracing/log_utxocache_flush.py
@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+
+import sys
+import ctypes
+from bcc import BPF, USDT
+
+"""Example logging Bitcoin Core utxo set cache flushes utilizing
+    the utxocache:flush tracepoint."""
+
+# USAGE:  ./contrib/tracing/log_utxocache_flush.py path/to/bitcoind
+
+# BCC: The C program to be compiled to an eBPF program (by BCC) and loaded into
+# a sandboxed Linux kernel VM.
+program = """
+# include <uapi/linux/ptrace.h>
+struct data_t
+{
+  u64 duration;
+  u32 mode;
+  u64 coins_count;
+  u64 coins_mem_usage;
+  bool is_flush_prune;
+  bool is_full_flush;
+};
+
+// BPF perf buffer to push the data to user space.
+BPF_PERF_OUTPUT(flush);
+
+int trace_flush(struct pt_regs *ctx) {
+  struct data_t data = {};
+  bpf_usdt_readarg(1, ctx, &data.duration);
+  bpf_usdt_readarg(2, ctx, &data.mode);
+  bpf_usdt_readarg(3, ctx, &data.coins_count);
+  bpf_usdt_readarg(4, ctx, &data.coins_mem_usage);
+  bpf_usdt_readarg(5, ctx, &data.is_flush_prune);
+  bpf_usdt_readarg(5, ctx, &data.is_full_flush);
+  flush.perf_submit(ctx, &data, sizeof(data));
+  return 0;
+}
+"""
+
+FLUSH_MODES = [
+    'NONE',
+    'IF_NEEDED',
+    'PERIODIC',
+    'ALWAYS'
+]
+
+
+class Data(ctypes.Structure):
+    # define output data structure corresponding to struct data_t
+    _fields_ = [
+        ("duration", ctypes.c_uint64),
+        ("mode", ctypes.c_uint32),
+        ("coins_count", ctypes.c_uint64),
+        ("coins_mem_usage", ctypes.c_uint64),
+        ("is_flush_prune", ctypes.c_bool),
+        ("is_full_flush", ctypes.c_bool)
+    ]
+
+
+def print_event(event):
+    print("%-15d %-10s %-15d %-15s %-8s %-8s" % (
+        event.duration,
+        FLUSH_MODES[event.mode],
+        event.coins_count,
+        "%.2f kB" % (event.coins_mem_usage/1000),
+        event.is_flush_prune,
+        event.is_full_flush
+    ))
+
+
+def main(bitcoind_path):
+    bitcoind_with_usdts = USDT(path=str(bitcoind_path))
+
+    # attaching the trace functions defined in the BPF program
+    # to the tracepoints
+    bitcoind_with_usdts.enable_probe(
+        probe="flush", fn_name="trace_flush")
+    b = BPF(text=program, usdt_contexts=[bitcoind_with_usdts])
+
+    def handle_flush(_, data, size):
+        """ Coins Flush handler.
+          Called each time coin caches and indexes are flushed."""
+        event = ctypes.cast(data, ctypes.POINTER(Data)).contents
+        print_event(event)
+
+    b["flush"].open_perf_buffer(handle_flush)
+    print("Logging utxocache flushes. Ctrl-C to end...")
+    print("%-15s %-10s %-15s %-15s %-8s %-8s" % ("Duration (µs)", "Mode",
+                                                 "Coins Count", "Memory Usage",
+                                                 "Prune", "Full Flush"))
+
+    while True:
+        try:
+            b.perf_buffer_poll()
+        except KeyboardInterrupt:
+            exit(0)
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("USAGE: ", sys.argv[0], "path/to/bitcoind")
+        exit(1)
+
+    path = sys.argv[1]
+    main(path)