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119 lines
4.2 KiB
119 lines
4.2 KiB
#!/usr/bin/env python
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import argparse
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from time import sleep
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from sys import argv
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import ctypes as ct
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from bcc import BPF, USDT
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import inspect
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import os
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# Parse command line arguments
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parser = argparse.ArgumentParser(description="Trace the latency of an operation using usdt probes.",
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formatter_class=argparse.RawDescriptionHelpFormatter)
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parser.add_argument("-p", "--pid", type=int, help="The id of the process to trace.")
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parser.add_argument("-f", "--filterstr", type=str, default="", help="The prefix filter for the operation input. If specified, only operations for which the input string starts with the filterstr are traced.")
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parser.add_argument("-v", "--verbose", dest="verbose", action="store_true", help="If true, will output verbose logging information.")
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parser.set_defaults(verbose=False)
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args = parser.parse_args()
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this_pid = int(args.pid)
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this_filter = str(args.filterstr)
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debugLevel=0
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if args.verbose:
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debugLevel=4
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# BPF program
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bpf_text_shared = "%s/bpf_text_shared.c" % os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe())))
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bpf_text = open(bpf_text_shared, 'r').read()
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bpf_text += """
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/**
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* @brief Contains the latency data w.r.t. the complete operation from request to response.
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*/
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struct end_data_t
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{
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u64 operation_id; ///< The id of the operation.
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char input[64]; ///< The request (input) string.
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char output[64]; ///< The response (output) string.
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u64 start; ///< The start timestamp of the operation.
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u64 end; ///< The end timestamp of the operation.
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u64 duration; ///< The duration of the operation.
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};
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/**
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* The output buffer, which will be used to push the latency event data to user space.
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*/
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BPF_PERF_OUTPUT(operation_event);
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/**
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* @brief Reads the operation response arguments, calculates the latency event data, and writes it to the user output buffer.
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* @param ctx The BPF context.
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*/
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int trace_operation_end(struct pt_regs* ctx)
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{
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u64 operation_id;
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bpf_usdt_readarg(1, ctx, &operation_id);
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struct start_data_t* start_data = start_hash.lookup(&operation_id);
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if (0 == start_data) {
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return 0;
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}
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struct end_data_t end_data = {};
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end_data.operation_id = operation_id;
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bpf_usdt_readarg_p(2, ctx, &end_data.output, sizeof(end_data.output));
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end_data.end = bpf_ktime_get_ns();
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end_data.start = start_data->start;
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end_data.duration = end_data.end - end_data.start;
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__builtin_memcpy(&end_data.input, start_data->input, sizeof(end_data.input));
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start_hash.delete(&end_data.operation_id);
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operation_event.perf_submit(ctx, &end_data, sizeof(end_data));
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return 0;
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}
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"""
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bpf_text = bpf_text.replace("FILTER_STRING", this_filter)
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if this_filter:
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bpf_text = bpf_text.replace("FILTER", "if (!filter(start_data.input)) { return 0; }")
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else:
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bpf_text = bpf_text.replace("FILTER", "")
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# Create USDT context
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print("Attaching probes to pid %d" % this_pid)
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usdt_ctx = USDT(pid=this_pid)
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usdt_ctx.enable_probe(probe="operation_start", fn_name="trace_operation_start")
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usdt_ctx.enable_probe(probe="operation_end", fn_name="trace_operation_end")
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# Create BPF context, load BPF program
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bpf_ctx = BPF(text=bpf_text, usdt_contexts=[usdt_ctx], debug=debugLevel)
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# Define latency event and print function
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class OperationEventData(ct.Structure):
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_fields_ = [("operation_id", ct.c_ulonglong),
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("input", ct.c_char * 64),
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("output", ct.c_char * 64),
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("start", ct.c_ulonglong),
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("end", ct.c_ulonglong),
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("duration", ct.c_ulonglong)]
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start = 0
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def print_event(cpu, data, size):
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global start
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event = ct.cast(data, ct.POINTER(OperationEventData)).contents
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if start == 0:
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start = event.start
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time_s = (float(event.start - start)) / 1000000000
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latency = (float(event.duration) / 1000)
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print("%-18.9f %-10d %-32s %-32s %16d %16d %16d" % (time_s, event.operation_id, event.input, event.output, event.start, event.end, latency))
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# Print header
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print("Tracing... Hit Ctrl-C to end.")
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print("%-18s %-10s %-32s %-32s %16s %16s %16s" % ("time(s)", "id", "input", "output", "start (ns)", "end (ns)", "duration (us)"))
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# Output latency events
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bpf_ctx["operation_event"].open_perf_buffer(print_event)
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while 1:
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bpf_ctx.perf_buffer_poll()
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