Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2021-10-15' into staging
[qemu.git] / scripts / userfaultfd-wrlat.py
1 #!/usr/bin/python3
2 #
3 # userfaultfd-wrlat Summarize userfaultfd write fault latencies.
4 # Events are continuously accumulated for the
5 # run, while latency distribution histogram is
6 # dumped each 'interval' seconds.
7 #
8 # For Linux, uses BCC, eBPF.
9 #
10 # USAGE: userfaultfd-lat [interval [count]]
11 #
12 # Copyright Virtuozzo GmbH, 2020
13 #
14 # Authors:
15 # Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
16 #
17 # This work is licensed under the terms of the GNU GPL, version 2 or
18 # later. See the COPYING file in the top-level directory.
19
20 from __future__ import print_function
21 from bcc import BPF
22 from ctypes import c_ushort, c_int, c_ulonglong
23 from time import sleep
24 from sys import argv
25
26 def usage():
27 print("USAGE: %s [interval [count]]" % argv[0])
28 exit()
29
30 # define BPF program
31 bpf_text = """
32 #include <uapi/linux/ptrace.h>
33 #include <linux/mm.h>
34
35 BPF_HASH(ev_start, u32, u64);
36 BPF_HISTOGRAM(ev_delta_hist, u64);
37
38 /* Trace UFFD page fault start event. */
39 static void do_event_start()
40 {
41 /* Using "(u32)" to drop group ID which is upper 32 bits */
42 u32 tid = (u32) bpf_get_current_pid_tgid();
43 u64 ts = bpf_ktime_get_ns();
44
45 ev_start.update(&tid, &ts);
46 }
47
48 /* Trace UFFD page fault end event. */
49 static void do_event_end()
50 {
51 /* Using "(u32)" to drop group ID which is upper 32 bits */
52 u32 tid = (u32) bpf_get_current_pid_tgid();
53 u64 ts = bpf_ktime_get_ns();
54 u64 *tsp;
55
56 tsp = ev_start.lookup(&tid);
57 if (tsp) {
58 u64 delta = ts - (*tsp);
59 /* Transform time delta to milliseconds */
60 ev_delta_hist.increment(bpf_log2l(delta / 1000000));
61 ev_start.delete(&tid);
62 }
63 }
64
65 /* KPROBE for handle_userfault(). */
66 int probe_handle_userfault(struct pt_regs *ctx, struct vm_fault *vmf,
67 unsigned long reason)
68 {
69 /* Trace only UFFD write faults. */
70 if (reason & VM_UFFD_WP) {
71 do_event_start();
72 }
73 return 0;
74 }
75
76 /* KRETPROBE for handle_userfault(). */
77 int retprobe_handle_userfault(struct pt_regs *ctx)
78 {
79 do_event_end();
80 return 0;
81 }
82 """
83
84 # arguments
85 interval = 10
86 count = -1
87 if len(argv) > 1:
88 try:
89 interval = int(argv[1])
90 if interval == 0:
91 raise
92 if len(argv) > 2:
93 count = int(argv[2])
94 except: # also catches -h, --help
95 usage()
96
97 # load BPF program
98 b = BPF(text=bpf_text)
99 # attach KRPOBEs
100 b.attach_kprobe(event="handle_userfault", fn_name="probe_handle_userfault")
101 b.attach_kretprobe(event="handle_userfault", fn_name="retprobe_handle_userfault")
102
103 # header
104 print("Tracing UFFD-WP write fault latency... Hit Ctrl-C to end.")
105
106 # output
107 loop = 0
108 do_exit = 0
109 while (1):
110 if count > 0:
111 loop += 1
112 if loop > count:
113 exit()
114 try:
115 sleep(interval)
116 except KeyboardInterrupt:
117 pass; do_exit = 1
118
119 print()
120 b["ev_delta_hist"].print_log2_hist("msecs")
121 if do_exit:
122 exit()