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c7243566d0
Add BCC/eBPF script to analyze userfaultfd write fault latency distribution. Signed-off-by: Andrey Gruzdev <andrey.gruzdev@virtuozzo.com> Reviewed-by: Peter Xu <peterx@redhat.com> Message-Id: <20210129101407.103458-6-andrey.gruzdev@virtuozzo.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
123 lines
2.9 KiB
Python
Executable File
123 lines
2.9 KiB
Python
Executable File
#!/usr/bin/python3
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#
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# userfaultfd-wrlat Summarize userfaultfd write fault latencies.
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# Events are continuously accumulated for the
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# run, while latency distribution histogram is
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# dumped each 'interval' seconds.
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#
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# For Linux, uses BCC, eBPF.
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#
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# USAGE: userfaultfd-lat [interval [count]]
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#
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# Copyright Virtuozzo GmbH, 2020
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#
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# Authors:
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# Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
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#
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# This work is licensed under the terms of the GNU GPL, version 2 or
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# later. See the COPYING file in the top-level directory.
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from __future__ import print_function
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from bcc import BPF
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from ctypes import c_ushort, c_int, c_ulonglong
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from time import sleep
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from sys import argv
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def usage():
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print("USAGE: %s [interval [count]]" % argv[0])
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exit()
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# define BPF program
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bpf_text = """
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#include <uapi/linux/ptrace.h>
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#include <linux/mm.h>
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BPF_HASH(ev_start, u32, u64);
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BPF_HISTOGRAM(ev_delta_hist, u64);
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/* Trace UFFD page fault start event. */
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static void do_event_start()
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{
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/* Using "(u32)" to drop group ID which is upper 32 bits */
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u32 tid = (u32) bpf_get_current_pid_tgid();
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u64 ts = bpf_ktime_get_ns();
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ev_start.update(&tid, &ts);
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}
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/* Trace UFFD page fault end event. */
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static void do_event_end()
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{
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/* Using "(u32)" to drop group ID which is upper 32 bits */
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u32 tid = (u32) bpf_get_current_pid_tgid();
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u64 ts = bpf_ktime_get_ns();
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u64 *tsp;
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tsp = ev_start.lookup(&tid);
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if (tsp) {
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u64 delta = ts - (*tsp);
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/* Transform time delta to milliseconds */
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ev_delta_hist.increment(bpf_log2l(delta / 1000000));
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ev_start.delete(&tid);
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}
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}
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/* KPROBE for handle_userfault(). */
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int probe_handle_userfault(struct pt_regs *ctx, struct vm_fault *vmf,
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unsigned long reason)
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{
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/* Trace only UFFD write faults. */
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if (reason & VM_UFFD_WP) {
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do_event_start();
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}
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return 0;
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}
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/* KRETPROBE for handle_userfault(). */
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int retprobe_handle_userfault(struct pt_regs *ctx)
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{
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do_event_end();
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return 0;
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}
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"""
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# arguments
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interval = 10
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count = -1
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if len(argv) > 1:
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try:
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interval = int(argv[1])
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if interval == 0:
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raise
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if len(argv) > 2:
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count = int(argv[2])
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except: # also catches -h, --help
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usage()
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# load BPF program
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b = BPF(text=bpf_text)
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# attach KRPOBEs
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b.attach_kprobe(event="handle_userfault", fn_name="probe_handle_userfault")
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b.attach_kretprobe(event="handle_userfault", fn_name="retprobe_handle_userfault")
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# header
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print("Tracing UFFD-WP write fault latency... Hit Ctrl-C to end.")
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# output
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loop = 0
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do_exit = 0
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while (1):
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if count > 0:
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loop += 1
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if loop > count:
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exit()
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try:
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sleep(interval)
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except KeyboardInterrupt:
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pass; do_exit = 1
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print()
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b["ev_delta_hist"].print_log2_hist("msecs")
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if do_exit:
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exit()
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