1#!/usr/bin/python 2# @lint-avoid-python-3-compatibility-imports 3# 4# mdflush Trace md flush events. 5# For Linux, uses BCC, eBPF. 6# 7# Todo: add more details of the flush (latency, I/O count). 8# 9# Copyright 2016 Netflix, Inc. 10# Licensed under the Apache License, Version 2.0 (the "License") 11# 12# 13-Feb-2015 Brendan Gregg Created this. 13 14from __future__ import print_function 15from bcc import BPF 16from time import strftime 17 18# load BPF program 19b = BPF(text=""" 20#include <uapi/linux/ptrace.h> 21#include <linux/sched.h> 22#include <linux/genhd.h> 23#include <linux/bio.h> 24 25struct data_t { 26 u64 pid; 27 char comm[TASK_COMM_LEN]; 28 char disk[DISK_NAME_LEN]; 29}; 30BPF_PERF_OUTPUT(events); 31 32int kprobe__md_flush_request(struct pt_regs *ctx, void *mddev, struct bio *bio) 33{ 34 struct data_t data = {}; 35 u32 pid = bpf_get_current_pid_tgid() >> 32; 36 data.pid = pid; 37 bpf_get_current_comm(&data.comm, sizeof(data.comm)); 38/* 39 * The following deals with a kernel version change (in mainline 4.14, although 40 * it may be backported to earlier kernels) with how the disk name is accessed. 41 * We handle both pre- and post-change versions here. Please avoid kernel 42 * version tests like this as much as possible: they inflate the code, test, 43 * and maintenance burden. 44 */ 45#ifdef bio_dev 46 struct gendisk *bi_disk = bio->bi_disk; 47#else 48 struct gendisk *bi_disk = bio->bi_bdev->bd_disk; 49#endif 50 bpf_probe_read_kernel(&data.disk, sizeof(data.disk), bi_disk->disk_name); 51 events.perf_submit(ctx, &data, sizeof(data)); 52 return 0; 53} 54""") 55 56# header 57print("Tracing md flush requests... Hit Ctrl-C to end.") 58print("%-8s %-7s %-16s %s" % ("TIME", "PID", "COMM", "DEVICE")) 59 60# process event 61def print_event(cpu, data, size): 62 event = b["events"].event(data) 63 print("%-8s %-7d %-16s %s" % (strftime("%H:%M:%S"), event.pid, 64 event.comm.decode('utf-8', 'replace'), 65 event.disk.decode('utf-8', 'replace'))) 66 67# read events 68b["events"].open_perf_buffer(print_event) 69while 1: 70 try: 71 b.perf_buffer_poll() 72 except KeyboardInterrupt: 73 exit() 74