#!/usr/bin/env python
# @lint-avoid-python-3-compatibility-imports
#
# cachetop Count cache kernel function calls per processes
# For Linux, uses BCC, eBPF.
#
# USAGE: cachetop
# Taken from cachestat by Brendan Gregg
#
# Copyright (c) 2016-present, Facebook, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 13-Jul-2016 Emmanuel Bretelle first version
# 17-Mar-2022 Rocky Xing Added PID filter support.
# 15-Feb-2023 Rong Tao Add writeback_dirty_{folio,page} tracepoints
from __future__ import absolute_import
from __future__ import division
# Do not import unicode_literals until #623 is fixed
# from __future__ import unicode_literals
from __future__ import print_function
from bcc import BPF
from collections import defaultdict
from time import strftime
import argparse
import curses
import pwd
import re
import signal
from time import sleep
FIELDS = (
"PID",
"UID",
"CMD",
"HITS",
"MISSES",
"DIRTIES",
"READ_HIT%",
"WRITE_HIT%"
)
DEFAULT_FIELD = "HITS"
DEFAULT_SORT_FIELD = FIELDS.index(DEFAULT_FIELD)
# signal handler
def signal_ignore(signal, frame):
print()
# Function to gather data from /proc/meminfo
# return dictionary for quicker lookup of both values
def get_meminfo():
result = {}
for line in open('/proc/meminfo'):
k = line.split(':', 3)
v = k[1].split()
result[k[0]] = int(v[0])
return result
def get_processes_stats(
bpf,
sort_field=DEFAULT_SORT_FIELD,
sort_reverse=False):
'''
Return a tuple containing:
buffer
cached
list of tuple with per process cache stats
'''
counts = bpf.get_table("counts")
stats = defaultdict(lambda: defaultdict(int))
for k, v in counts.items():
stats["%d-%d-%s" % (k.pid, k.uid, k.comm.decode('utf-8', 'replace'))][k.nf] = v.value
stats_list = []
for pid, count in sorted(stats.items(), key=lambda stat: stat[0]):
rtaccess = 0
wtaccess = 0
mpa = 0
mbd = 0
apcl = 0
apd = 0
access = 0
misses = 0
rhits = 0
whits = 0
for k, v in count.items():
if k == 0: # NF_APCL
apcl = max(0, v)
if k == 1: # NF_MPA
mpa = max(0, v)
if k == 2: # NF_MBD
mbd = max(0, v)
if k == 3: # NF_APD
apd = max(0, v)
# access = total cache access incl. reads(mpa) and writes(mbd)
# misses = total of add to lru which we do when we write(mbd)
# and also the mark the page dirty(same as mbd)
access = (mpa + mbd)
misses = (apcl + apd)
# rtaccess is the read hit % during the sample period.
# wtaccess is the write hit % during the sample period.
if mpa > 0:
rtaccess = float(mpa) / (access + misses)
if apcl > 0:
wtaccess = float(apcl) / (access + misses)
if wtaccess != 0:
whits = 100 * wtaccess
if rtaccess != 0:
rhits = 100 * rtaccess
_pid, uid, comm = pid.split('-', 2)
stats_list.append(
(int(_pid), uid, comm,
access, misses, mbd,
rhits, whits))
stats_list = sorted(
stats_list, key=lambda stat: stat[sort_field], reverse=sort_reverse
)
counts.clear()
return stats_list
def handle_loop(stdscr, args):
# don't wait on key press
stdscr.nodelay(1)
# set default sorting field
sort_field = FIELDS.index(DEFAULT_FIELD)
sort_reverse = True
# load BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
struct key_t {
// NF_{APCL,MPA,MBD,APD}
u64 nf;
u32 pid;
u32 uid;
char comm[16];
};
enum {
NF_APCL,
NF_MPA,
NF_MBD,
NF_APD,
};
BPF_HASH(counts, struct key_t);
static int __do_count(void *ctx, u64 nf) {
u32 pid = bpf_get_current_pid_tgid() >> 32;
if (FILTER_PID)
return 0;
struct key_t key = {};
u32 uid = bpf_get_current_uid_gid();
key.nf = nf;
key.pid = pid;
key.uid = uid;
bpf_get_current_comm(&(key.comm), 16);
counts.increment(key);
return 0;
}
int do_count_apcl(struct pt_regs *ctx) {
return __do_count(ctx, NF_APCL);
}
int do_count_mpa(struct pt_regs *ctx) {
return __do_count(ctx, NF_MPA);
}
int do_count_mbd(struct pt_regs *ctx) {
return __do_count(ctx, NF_MBD);
}
int do_count_apd(struct pt_regs *ctx) {
return __do_count(ctx, NF_APD);
}
int do_count_apd_tp(void *ctx) {
return __do_count(ctx, NF_APD);
}
"""
if args.pid:
bpf_text = bpf_text.replace('FILTER_PID', 'pid != %d' % args.pid)
else:
bpf_text = bpf_text.replace('FILTER_PID', '0')
b = BPF(text=bpf_text)
b.attach_kprobe(event="add_to_page_cache_lru", fn_name="do_count_apcl")
b.attach_kprobe(event="mark_page_accessed", fn_name="do_count_mpa")
b.attach_kprobe(event="mark_buffer_dirty", fn_name="do_count_mbd")
# Function account_page_dirtied() is changed to folio_account_dirtied() in 5.15.
# Introduce tracepoint writeback_dirty_{page,folio}
if BPF.get_kprobe_functions(b'folio_account_dirtied'):
b.attach_kprobe(event="folio_account_dirtied", fn_name="do_count_apd")
elif BPF.get_kprobe_functions(b'account_page_dirtied'):
b.attach_kprobe(event="account_page_dirtied", fn_name="do_count_apd")
elif BPF.tracepoint_exists("writeback", "writeback_dirty_folio"):
b.attach_tracepoint(tp="writeback:writeback_dirty_folio", fn_name="do_count_apd_tp")
elif BPF.tracepoint_exists("writeback", "writeback_dirty_page"):
b.attach_tracepoint(tp="writeback:writeback_dirty_page", fn_name="do_count_apd_tp")
else:
raise Exception("Failed to attach kprobe %s or %s and any tracepoint" %
("folio_account_dirtied", "account_page_dirtied"))
exiting = 0
while 1:
s = stdscr.getch()
if s == ord('q'):
exiting = 1
elif s == ord('r'):
sort_reverse = not sort_reverse
elif s == ord('<'):
sort_field = max(0, sort_field - 1)
elif s == ord('>'):
sort_field = min(len(FIELDS) - 1, sort_field + 1)
try:
sleep(args.interval)
except KeyboardInterrupt:
exiting = 1
# as cleanup can take many seconds, trap Ctrl-C:
signal.signal(signal.SIGINT, signal_ignore)
# Get memory info
mem = get_meminfo()
cached = int(mem["Cached"]) / 1024
buff = int(mem["Buffers"]) / 1024
process_stats = get_processes_stats(
b,
sort_field=sort_field,
sort_reverse=sort_reverse)
stdscr.clear()
stdscr.addstr(
0, 0,
"%-8s Buffers MB: %.0f / Cached MB: %.0f "
"/ Sort: %s / Order: %s" % (
strftime("%H:%M:%S"), buff, cached, FIELDS[sort_field],
sort_reverse and "descending" or "ascending"
)
)
# header
stdscr.addstr(
1, 0,
"{0:8} {1:8} {2:16} {3:8} {4:8} {5:8} {6:10} {7:10}".format(
*FIELDS
),
curses.A_REVERSE
)
(height, width) = stdscr.getmaxyx()
for i, stat in enumerate(process_stats):
uid = int(stat[1])
try:
username = pwd.getpwuid(uid)[0]
except KeyError:
# `pwd` throws a KeyError if the user cannot be found. This can
# happen e.g. when the process is running in a cgroup that has
# different users from the host.
username = 'UNKNOWN({})'.format(uid)
stdscr.addstr(
i + 2, 0,
"{0:8} {username:8.8} {2:16} {3:8} {4:8} "
"{5:8} {6:9.1f}% {7:9.1f}%".format(
*stat, username=username
)
)
if i > height - 4:
break
stdscr.refresh()
if exiting:
print("Detaching...")
return
def parse_arguments():
parser = argparse.ArgumentParser(
description='Show Linux page cache hit/miss statistics including read '
'and write hit % per processes in a UI like top.'
)
parser.add_argument("-p", "--pid", type=int, metavar="PID",
help="trace this PID only")
parser.add_argument(
'interval', type=int, default=5, nargs='?',
help='Interval between probes.'
)
args = parser.parse_args()
return args
args = parse_arguments()
curses.wrapper(handle_loop, args)
