| 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 bcc import BPF |
| 21 | from ctypes import c_ushort, c_int, c_ulonglong |
| 22 | from time import sleep |
| 23 | from sys import argv |
| 24 | |
| 25 | def usage(): |
| 26 | print("USAGE: %s [interval [count]]" % argv[0]) |
| 27 | exit() |
| 28 | |
| 29 | # define BPF program |
| 30 | bpf_text = """ |
| 31 | #include <uapi/linux/ptrace.h> |
| 32 | #include <linux/mm.h> |
| 33 | |
| 34 | BPF_HASH(ev_start, u32, u64); |
| 35 | BPF_HISTOGRAM(ev_delta_hist, u64); |
| 36 | |
| 37 | /* Trace UFFD page fault start event. */ |
| 38 | static void do_event_start() |
| 39 | { |
| 40 | /* Using "(u32)" to drop group ID which is upper 32 bits */ |
| 41 | u32 tid = (u32) bpf_get_current_pid_tgid(); |
| 42 | u64 ts = bpf_ktime_get_ns(); |
| 43 | |
| 44 | ev_start.update(&tid, &ts); |
| 45 | } |
| 46 | |
| 47 | /* Trace UFFD page fault end event. */ |
| 48 | static void do_event_end() |
| 49 | { |
| 50 | /* Using "(u32)" to drop group ID which is upper 32 bits */ |
| 51 | u32 tid = (u32) bpf_get_current_pid_tgid(); |
| 52 | u64 ts = bpf_ktime_get_ns(); |
| 53 | u64 *tsp; |
| 54 | |
| 55 | tsp = ev_start.lookup(&tid); |
| 56 | if (tsp) { |
| 57 | u64 delta = ts - (*tsp); |
| 58 | /* Transform time delta to milliseconds */ |
| 59 | ev_delta_hist.increment(bpf_log2l(delta / 1000000)); |
| 60 | ev_start.delete(&tid); |
| 61 | } |
| 62 | } |
| 63 | |
| 64 | /* KPROBE for handle_userfault(). */ |
| 65 | int probe_handle_userfault(struct pt_regs *ctx, struct vm_fault *vmf, |
| 66 | unsigned long reason) |
| 67 | { |
| 68 | /* Trace only UFFD write faults. */ |
| 69 | if (reason & VM_UFFD_WP) { |
| 70 | do_event_start(); |
| 71 | } |
| 72 | return 0; |
| 73 | } |
| 74 | |
| 75 | /* KRETPROBE for handle_userfault(). */ |
| 76 | int retprobe_handle_userfault(struct pt_regs *ctx) |
| 77 | { |
| 78 | do_event_end(); |
| 79 | return 0; |
| 80 | } |
| 81 | """ |
| 82 | |
| 83 | # arguments |
| 84 | interval = 10 |
| 85 | count = -1 |
| 86 | if len(argv) > 1: |
| 87 | try: |
| 88 | interval = int(argv[1]) |
| 89 | if interval == 0: |
| 90 | raise |
| 91 | if len(argv) > 2: |
| 92 | count = int(argv[2]) |
| 93 | except: # also catches -h, --help |
| 94 | usage() |
| 95 | |
| 96 | # load BPF program |
| 97 | b = BPF(text=bpf_text) |
| 98 | # attach KRPOBEs |
| 99 | b.attach_kprobe(event="handle_userfault", fn_name="probe_handle_userfault") |
| 100 | b.attach_kretprobe(event="handle_userfault", fn_name="retprobe_handle_userfault") |
| 101 | |
| 102 | # header |
| 103 | print("Tracing UFFD-WP write fault latency... Hit Ctrl-C to end.") |
| 104 | |
| 105 | # output |
| 106 | loop = 0 |
| 107 | do_exit = 0 |
| 108 | while (1): |
| 109 | if count > 0: |
| 110 | loop += 1 |
| 111 | if loop > count: |
| 112 | exit() |
| 113 | try: |
| 114 | sleep(interval) |
| 115 | except KeyboardInterrupt: |
| 116 | pass; do_exit = 1 |
| 117 | |
| 118 | print() |
| 119 | b["ev_delta_hist"].print_log2_hist("msecs") |
| 120 | if do_exit: |
| 121 | exit() |