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#! /usr/bin/python3
# @lint-avoid-python-3-compatibility-imports
#
# btrfsdist Summarize btrfs operation latency.
# For Linux, uses BCC, eBPF.
#
# USAGE: btrfsdist [-h] [-T] [-m] [-p PID] [interval] [count]
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 15-Feb-2016 Brendan Gregg Created this.
from __future__ import print_function
from bcc import BPF
from time import sleep, strftime
import argparse
# symbols
kallsyms = "/proc/kallsyms"
# arguments
examples = """examples:
./btrfsdist # show operation latency as a histogram
./btrfsdist -p 181 # trace PID 181 only
./btrfsdist 1 10 # print 1 second summaries, 10 times
./btrfsdist -m 5 # 5s summaries, milliseconds
"""
parser = argparse.ArgumentParser(
description="Summarize btrfs operation latency",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-T", "--notimestamp", action="store_true",
help="don't include timestamp on interval output")
parser.add_argument("-m", "--milliseconds", action="store_true",
help="output in milliseconds")
parser.add_argument("-p", "--pid",
help="trace this PID only")
parser.add_argument("interval", nargs="?",
help="output interval, in seconds")
parser.add_argument("count", nargs="?", default=99999999,
help="number of outputs")
parser.add_argument("--ebpf", action="store_true",
help=argparse.SUPPRESS)
args = parser.parse_args()
pid = args.pid
countdown = int(args.count)
if args.milliseconds:
factor = 1000000
label = "msecs"
else:
factor = 1000
label = "usecs"
if args.interval and int(args.interval) == 0:
print("ERROR: interval 0. Exiting.")
exit()
debug = 0
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/fs.h>
#include <linux/sched.h>
#define OP_NAME_LEN 8
typedef struct dist_key {
char op[OP_NAME_LEN];
u64 slot;
} dist_key_t;
BPF_HASH(start, u32);
BPF_HISTOGRAM(dist, dist_key_t);
// time operation
int trace_entry(struct pt_regs *ctx)
{
u64 pid_tgid = bpf_get_current_pid_tgid();
u32 pid = pid_tgid >> 32;
u32 tid = (u32)pid_tgid;
if (FILTER_PID)
return 0;
u64 ts = bpf_ktime_get_ns();
start.update(&tid, &ts);
return 0;
}
// The current btrfs (Linux 4.5) uses generic_file_read_iter() instead of it's
// own read function. So we need to trace that and then filter on btrfs, which
// I do by checking file->f_op.
int trace_read_entry(struct pt_regs *ctx, struct kiocb *iocb)
{
u64 pid_tgid = bpf_get_current_pid_tgid();
u32 pid = pid_tgid >> 32;
u32 tid = (u32)pid_tgid;
if (FILTER_PID)
return 0;
// btrfs filter on file->f_op == btrfs_file_operations
struct file *fp = iocb->ki_filp;
if ((u64)fp->f_op != BTRFS_FILE_OPERATIONS)
return 0;
u64 ts = bpf_ktime_get_ns();
start.update(&tid, &ts);
return 0;
}
// The current btrfs (Linux 4.5) uses generic_file_open(), instead of it's own
// function. Same as with reads. Trace the generic path and filter:
int trace_open_entry(struct pt_regs *ctx, struct inode *inode,
struct file *file)
{
u64 pid_tgid = bpf_get_current_pid_tgid();
u32 pid = pid_tgid >> 32;
u32 tid = (u32)pid_tgid;
if (FILTER_PID)
return 0;
// btrfs filter on file->f_op == btrfs_file_operations
if ((u64)file->f_op != BTRFS_FILE_OPERATIONS)
return 0;
u64 ts = bpf_ktime_get_ns();
start.update(&tid, &ts);
return 0;
}
static int trace_return(struct pt_regs *ctx, const char *op)
{
u64 *tsp;
u64 pid_tgid = bpf_get_current_pid_tgid();
u32 pid = pid_tgid >> 32;
u32 tid = (u32)pid_tgid;
// fetch timestamp and calculate delta
tsp = start.lookup(&tid);
if (tsp == 0) {
return 0; // missed start or filtered
}
u64 delta = (bpf_ktime_get_ns() - *tsp) / FACTOR;
// store as histogram
dist_key_t key = {.slot = bpf_log2l(delta)};
__builtin_memcpy(&key.op, op, sizeof(key.op));
dist.atomic_increment(key);
start.delete(&tid);
return 0;
}
int trace_read_return(struct pt_regs *ctx)
{
char *op = "read";
return trace_return(ctx, op);
}
int trace_write_return(struct pt_regs *ctx)
{
char *op = "write";
return trace_return(ctx, op);
}
int trace_open_return(struct pt_regs *ctx)
{
char *op = "open";
return trace_return(ctx, op);
}
int trace_fsync_return(struct pt_regs *ctx)
{
char *op = "fsync";
return trace_return(ctx, op);
}
"""
# code replacements
with open(kallsyms) as syms:
ops = ''
for line in syms:
a = line.rstrip().split()
(addr, name) = (a[0], a[2])
name = name.split("\t")[0]
if name == "btrfs_file_operations":
ops = "0x" + addr
break
if ops == '':
print("ERROR: no btrfs_file_operations in /proc/kallsyms. Exiting.")
print("HINT: the kernel should be built with CONFIG_KALLSYMS_ALL.")
exit()
bpf_text = bpf_text.replace('BTRFS_FILE_OPERATIONS', ops)
bpf_text = bpf_text.replace('FACTOR', str(factor))
if args.pid:
bpf_text = bpf_text.replace('FILTER_PID', 'pid != %s' % pid)
else:
bpf_text = bpf_text.replace('FILTER_PID', '0')
if debug or args.ebpf:
print(bpf_text)
if args.ebpf:
exit()
# load BPF program
b = BPF(text=bpf_text)
# Common file functions. See earlier comment about generic_file_read_iter().
b.attach_kprobe(event="generic_file_read_iter", fn_name="trace_read_entry")
b.attach_kprobe(event="btrfs_file_write_iter", fn_name="trace_entry")
b.attach_kprobe(event="generic_file_open", fn_name="trace_open_entry")
b.attach_kprobe(event="btrfs_sync_file", fn_name="trace_entry")
b.attach_kretprobe(event="generic_file_read_iter", fn_name="trace_read_return")
b.attach_kretprobe(event="btrfs_file_write_iter", fn_name="trace_write_return")
b.attach_kretprobe(event="generic_file_open", fn_name="trace_open_return")
b.attach_kretprobe(event="btrfs_sync_file", fn_name="trace_fsync_return")
print("Tracing btrfs operation latency... Hit Ctrl-C to end.")
# output
exiting = 0
dist = b.get_table("dist")
while (1):
try:
if args.interval:
sleep(int(args.interval))
else:
sleep(99999999)
except KeyboardInterrupt:
exiting = 1
print()
if args.interval and (not args.notimestamp):
print(strftime("%H:%M:%S:"))
dist.print_log2_hist(label, "operation", section_print_fn=bytes.decode)
dist.clear()
countdown -= 1
if exiting or countdown == 0:
exit()
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