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142 lines
4.0 KiB
142 lines
4.0 KiB
#!/usr/bin/env python
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#
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# gethostlatency Show latency for getaddrinfo/gethostbyname[2] calls.
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# For Linux, uses BCC, eBPF. Embedded C.
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#
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# This can be useful for identifying DNS latency, by identifying which
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# remote host name lookups were slow, and by how much.
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#
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# This uses dynamic tracing of user-level functions and registers, and may
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# need modifications to match your software and processor architecture.
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#
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# Copyright 2016 Netflix, Inc.
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# Licensed under the Apache License, Version 2.0 (the "License")
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#
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# 28-Jan-2016 Brendan Gregg Created this.
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# 30-Mar-2016 Allan McAleavy updated for BPF_PERF_OUTPUT
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from __future__ import print_function
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from bcc import BPF
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from time import strftime
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import argparse
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import ctypes as ct
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examples = """examples:
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./gethostlatency # trace all TCP accept()s
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./gethostlatency -p 181 # only trace PID 181
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"""
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parser = argparse.ArgumentParser(
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description="Show latency for getaddrinfo/gethostbyname[2] calls",
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formatter_class=argparse.RawDescriptionHelpFormatter,
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epilog=examples)
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parser.add_argument("-p", "--pid", help="trace this PID only", type=int,
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default=-1)
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parser.add_argument("--ebpf", action="store_true",
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help=argparse.SUPPRESS)
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args = parser.parse_args()
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# load BPF program
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bpf_text = """
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#include <uapi/linux/ptrace.h>
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#include <linux/sched.h>
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struct val_t {
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u32 pid;
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char comm[TASK_COMM_LEN];
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char host[80];
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u64 ts;
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};
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struct data_t {
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u32 pid;
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u64 delta;
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char comm[TASK_COMM_LEN];
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char host[80];
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};
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BPF_HASH(start, u32, struct val_t);
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BPF_PERF_OUTPUT(events);
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int do_entry(struct pt_regs *ctx) {
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if (!PT_REGS_PARM1(ctx))
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return 0;
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struct val_t val = {};
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u32 pid = bpf_get_current_pid_tgid();
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if (bpf_get_current_comm(&val.comm, sizeof(val.comm)) == 0) {
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bpf_probe_read(&val.host, sizeof(val.host),
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(void *)PT_REGS_PARM1(ctx));
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val.pid = bpf_get_current_pid_tgid();
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val.ts = bpf_ktime_get_ns();
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start.update(&pid, &val);
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}
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return 0;
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}
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int do_return(struct pt_regs *ctx) {
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struct val_t *valp;
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struct data_t data = {};
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u64 delta;
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u32 pid = bpf_get_current_pid_tgid();
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u64 tsp = bpf_ktime_get_ns();
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valp = start.lookup(&pid);
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if (valp == 0)
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return 0; // missed start
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bpf_probe_read(&data.comm, sizeof(data.comm), valp->comm);
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bpf_probe_read(&data.host, sizeof(data.host), (void *)valp->host);
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data.pid = valp->pid;
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data.delta = tsp - valp->ts;
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events.perf_submit(ctx, &data, sizeof(data));
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start.delete(&pid);
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return 0;
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}
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"""
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if args.ebpf:
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print(bpf_text)
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exit()
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b = BPF(text=bpf_text)
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b.attach_uprobe(name="c", sym="getaddrinfo", fn_name="do_entry", pid=args.pid)
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b.attach_uprobe(name="c", sym="gethostbyname", fn_name="do_entry",
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pid=args.pid)
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b.attach_uprobe(name="c", sym="gethostbyname2", fn_name="do_entry",
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pid=args.pid)
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b.attach_uretprobe(name="c", sym="getaddrinfo", fn_name="do_return",
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pid=args.pid)
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b.attach_uretprobe(name="c", sym="gethostbyname", fn_name="do_return",
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pid=args.pid)
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b.attach_uretprobe(name="c", sym="gethostbyname2", fn_name="do_return",
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pid=args.pid)
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TASK_COMM_LEN = 16 # linux/sched.h
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class Data(ct.Structure):
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_fields_ = [
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("pid", ct.c_ulonglong),
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("delta", ct.c_ulonglong),
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("comm", ct.c_char * TASK_COMM_LEN),
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("host", ct.c_char * 80)
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]
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# header
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print("%-9s %-6s %-16s %10s %s" % ("TIME", "PID", "COMM", "LATms", "HOST"))
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def print_event(cpu, data, size):
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event = ct.cast(data, ct.POINTER(Data)).contents
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print("%-9s %-6d %-16s %10.2f %s" % (strftime("%H:%M:%S"), event.pid,
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event.comm.decode('utf-8', 'replace'), (float(event.delta) / 1000000),
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event.host.decode('utf-8', 'replace')))
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# loop with callback to print_event
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b["events"].open_perf_buffer(print_event)
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while 1:
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try:
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b.perf_buffer_poll()
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except KeyboardInterrupt:
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exit()
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