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78 lines
2.2 KiB
78 lines
2.2 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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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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# load BPF program
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bpf_text = """
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#include <uapi/linux/ptrace.h>
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struct val_t {
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char host[80];
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u64 ts;
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};
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BPF_HASH(start, u32, struct val_t);
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int do_entry(struct pt_regs *ctx) {
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if (!ctx->di)
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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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bpf_probe_read(&val.host, sizeof(val.host), (void *)ctx->di);
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val.ts = bpf_ktime_get_ns();
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start.update(&pid, &val);
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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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u64 delta;
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u32 pid = bpf_get_current_pid_tgid();
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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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delta = (bpf_ktime_get_ns() - valp->ts) / 1000;
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bpf_trace_printk("%d %s\\n", delta, valp->host);
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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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b = BPF(text=bpf_text)
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b.attach_uprobe(name="c", sym="getaddrinfo", fn_name="do_entry")
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b.attach_uprobe(name="c", sym="gethostbyname", fn_name="do_entry")
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b.attach_uprobe(name="c", sym="gethostbyname2", fn_name="do_entry")
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b.attach_uretprobe(name="c", sym="getaddrinfo", fn_name="do_return")
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b.attach_uretprobe(name="c", sym="gethostbyname", fn_name="do_return")
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b.attach_uretprobe(name="c", sym="gethostbyname2", fn_name="do_return")
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# header
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print("%-9s %-6s %-12s %6s %s" % ("TIME", "PID", "COMM", "LATms", "HOST"))
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# format output
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while 1:
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try:
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(task, pid, cpu, flags, ts, msg) = b.trace_fields()
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except ValueError:
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continue
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(delta, host) = msg.split(" ")
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deltams = int(delta) / 1000
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print("%-9s %-6d %-12.12s %6.2f %s" % (strftime("%H:%M:%S"), pid, task,
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deltams, host))
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