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| Current File : //sbin/readahead-bpfcc |
#! /usr/bin/python3
# @lint-avoid-python-3-compatibility-imports
#
# readahead Show performance of read-ahead cache
# For Linux, uses BCC, eBPF
#
# Copyright (c) 2020 Suchakra Sharma <mail@suchakra.in>
# Licensed under the Apache License, Version 2.0 (the "License")
# This was originally created for the BPF Performance Tools book
# published by Addison Wesley. ISBN-13: 9780136554820
# When copying or porting, include this comment.
#
# 20-Aug-2020 Suchakra Sharma Ported from bpftrace to BCC
# 17-Sep-2021 Hengqi Chen Migrated to kfunc
# 30-Jan-2023 Rong Tao Support more kfunc/kprobe, introduce folio
from __future__ import print_function
from bcc import BPF
from time import sleep
import ctypes as ct
import argparse
# arguments
examples = """examples:
./readahead -d 20 # monitor for 20 seconds and generate stats
"""
parser = argparse.ArgumentParser(
description="Monitor performance of read ahead cache",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-d", "--duration", type=int,
help="total duration to monitor for, in seconds")
args = parser.parse_args()
if not args.duration:
args.duration = 99999999
# BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/mm_types.h>
#include <linux/mm.h>
BPF_HASH(flag, u32, u8); // used to track if we are in do_page_cache_readahead()
BPF_HASH(birth, struct page*, u64); // used to track timestamps of cache alloc'ed page
BPF_ARRAY(pages); // increment/decrement readahead pages
BPF_HISTOGRAM(dist);
"""
bpf_text_kprobe = """
int entry__do_page_cache_readahead(struct pt_regs *ctx) {
u32 pid;
u8 one = 1;
pid = bpf_get_current_pid_tgid();
flag.update(&pid, &one);
return 0;
}
int exit__do_page_cache_readahead(struct pt_regs *ctx) {
u32 pid;
u8 zero = 0;
pid = bpf_get_current_pid_tgid();
flag.update(&pid, &zero);
return 0;
}
int exit__page_cache_alloc(struct pt_regs *ctx) {
u32 pid;
u64 ts;
struct page *retval = (struct page*) GET_RETVAL_PAGE;
u32 zero = 0; // static key for accessing pages[0]
pid = bpf_get_current_pid_tgid();
u8 *f = flag.lookup(&pid);
if (f != NULL && *f == 1) {
ts = bpf_ktime_get_ns();
birth.update(&retval, &ts);
pages.atomic_increment(zero);
}
return 0;
}
int entry_mark_page_accessed(struct pt_regs *ctx) {
u64 ts, delta;
struct page *arg0 = (struct page *) PT_REGS_PARM1(ctx);
u32 zero = 0; // static key for accessing pages[0]
u64 *bts = birth.lookup(&arg0);
if (bts != NULL) {
delta = bpf_ktime_get_ns() - *bts;
dist.atomic_increment(bpf_log2l(delta/1000000));
pages.atomic_increment(zero, -1);
birth.delete(&arg0); // remove the entry from hashmap
}
return 0;
}
"""
bpf_text_kfunc = """
KFUNC_PROBE(RA_FUNC)
{
u32 pid = bpf_get_current_pid_tgid();
u8 one = 1;
flag.update(&pid, &one);
return 0;
}
KRETFUNC_PROBE(RA_FUNC)
{
u32 pid = bpf_get_current_pid_tgid();
u8 zero = 0;
flag.update(&pid, &zero);
return 0;
}
KFUNC_PROBE(mark_page_accessed, struct page *arg0)
{
u64 ts, delta;
u32 zero = 0; // static key for accessing pages[0]
u64 *bts = birth.lookup(&arg0);
if (bts != NULL) {
delta = bpf_ktime_get_ns() - *bts;
dist.atomic_increment(bpf_log2l(delta/1000000));
pages.atomic_increment(zero, -1);
birth.delete(&arg0); // remove the entry from hashmap
}
return 0;
}
"""
bpf_text_kfunc_cache_alloc_ret_page = """
KRETFUNC_PROBE(__page_cache_alloc, gfp_t gfp, struct page *retval)
{
u64 ts;
u32 zero = 0; // static key for accessing pages[0]
u32 pid = bpf_get_current_pid_tgid();
u8 *f = flag.lookup(&pid);
if (f != NULL && *f == 1) {
ts = bpf_ktime_get_ns();
birth.update(&retval, &ts);
pages.atomic_increment(zero);
}
return 0;
}
"""
bpf_text_kfunc_cache_alloc_ret_folio = """
KRETFUNC_PROBE(filemap_alloc_folio, gfp_t gfp, unsigned int order,
struct folio *retval)
{
u64 ts;
u32 zero = 0; // static key for accessing pages[0]
u32 pid = bpf_get_current_pid_tgid();
u8 *f = flag.lookup(&pid);
struct page *page = folio_page(retval, 0);
if (f != NULL && *f == 1) {
ts = bpf_ktime_get_ns();
birth.update(&page, &ts);
pages.atomic_increment(zero);
}
return 0;
}
"""
if BPF.support_kfunc():
if BPF.get_kprobe_functions(b"__do_page_cache_readahead"):
ra_func = "__do_page_cache_readahead"
elif BPF.get_kprobe_functions(b"do_page_cache_ra"):
ra_func = "do_page_cache_ra"
elif BPF.get_kprobe_functions(b"page_cache_ra_order"):
ra_func = "page_cache_ra_order"
else:
print("Not found any kfunc.")
exit()
bpf_text += bpf_text_kfunc.replace("RA_FUNC", ra_func)
if BPF.get_kprobe_functions(b"__page_cache_alloc"):
bpf_text += bpf_text_kfunc_cache_alloc_ret_page
else:
bpf_text += bpf_text_kfunc_cache_alloc_ret_folio
b = BPF(text=bpf_text)
else:
bpf_text += bpf_text_kprobe
if BPF.get_kprobe_functions(b"__do_page_cache_readahead"):
ra_event = "__do_page_cache_readahead"
elif BPF.get_kprobe_functions(b"do_page_cache_ra"):
ra_event = "do_page_cache_ra"
elif BPF.get_kprobe_functions(b"page_cache_ra_order"):
ra_event = "page_cache_ra_order"
else:
print("Not found any kprobe.")
exit()
if BPF.get_kprobe_functions(b"__page_cache_alloc"):
cache_func = "__page_cache_alloc"
bpf_text = bpf_text.replace('GET_RETVAL_PAGE', 'PT_REGS_RC(ctx)')
else:
cache_func = "filemap_alloc_folio"
bpf_text = bpf_text.replace('GET_RETVAL_PAGE', 'folio_page((struct folio *)PT_REGS_RC(ctx), 0)')
b = BPF(text=bpf_text)
b.attach_kprobe(event=ra_event, fn_name="entry__do_page_cache_readahead")
b.attach_kretprobe(event=ra_event, fn_name="exit__do_page_cache_readahead")
b.attach_kretprobe(event=cache_func, fn_name="exit__page_cache_alloc")
b.attach_kprobe(event="mark_page_accessed", fn_name="entry_mark_page_accessed")
# header
print("Tracing... Hit Ctrl-C to end.")
# print
def print_stats():
print()
print("Read-ahead unused pages: %d" % (b["pages"][ct.c_ulong(0)].value))
print("Histogram of read-ahead used page age (ms):")
print("")
b["dist"].print_log2_hist("age (ms)")
b["dist"].clear()
b["pages"].clear()
while True:
try:
sleep(args.duration)
print_stats()
except KeyboardInterrupt:
print_stats()
break
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