1#!/usr/bin/env 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# define BPF program 19bpf_text=""" 20#include <uapi/linux/ptrace.h> 21#include <linux/sched.h> 22#include <linux/blkdev.h> 23#include <linux/bio.h> 24 25struct data_t { 26 u32 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 data.pid = bpf_get_current_pid_tgid() >> 32; 36 bpf_get_current_comm(&data.comm, sizeof(data.comm)); 37/* 38 * The following deals with kernel version changes (in mainline 4.14 and 5.12, although 39 * it may be backported to earlier kernels) with how the disk name is accessed. 40 * We handle both pre- and post-change versions here. Please avoid kernel 41 * version tests like this as much as possible: they inflate the code, test, 42 * and maintenance burden. 43 */ 44#ifdef bio_dev 45 struct gendisk *bi_disk = bio->__BI_DISK__; 46#else 47 struct gendisk *bi_disk = bio->bi_bdev->bd_disk; 48#endif 49 bpf_probe_read_kernel(&data.disk, sizeof(data.disk), bi_disk->disk_name); 50 events.perf_submit(ctx, &data, sizeof(data)); 51 return 0; 52} 53""" 54 55if BPF.kernel_struct_has_field('bio', 'bi_bdev') == 1: 56 bpf_text = bpf_text.replace('__BI_DISK__', 'bi_bdev->bd_disk') 57else: 58 bpf_text = bpf_text.replace('__BI_DISK__', 'bi_disk') 59 60# initialize BPF 61b = BPF(text=bpf_text) 62 63# header 64print("Tracing md flush requests... Hit Ctrl-C to end.") 65print("%-8s %-7s %-16s %s" % ("TIME", "PID", "COMM", "DEVICE")) 66 67# process event 68def print_event(cpu, data, size): 69 event = b["events"].event(data) 70 print("%-8s %-7d %-16s %s" % (strftime("%H:%M:%S"), event.pid, 71 event.comm.decode('utf-8', 'replace'), 72 event.disk.decode('utf-8', 'replace'))) 73 74# read events 75b["events"].open_perf_buffer(print_event) 76while 1: 77 try: 78 b.perf_buffer_poll() 79 except KeyboardInterrupt: 80 exit() 81