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#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# mdflush Trace md flush events.
# For Linux, uses BCC, eBPF.
#
# Todo: add more details of the flush (latency, I/O count).
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 13-Feb-2015 Brendan Gregg Created this.
from __future__ import print_function
from bcc import BPF
from time import strftime
# load BPF program
b = BPF(text="""
#include <uapi/linux/ptrace.h>
#include <linux/sched.h>
#include <linux/genhd.h>
#include <linux/bio.h>
struct data_t {
u64 pid;
char comm[TASK_COMM_LEN];
char disk[DISK_NAME_LEN];
};
BPF_PERF_OUTPUT(events);
int kprobe__md_flush_request(struct pt_regs *ctx, void *mddev, struct bio *bio)
{
struct data_t data = {};
u32 pid = bpf_get_current_pid_tgid() >> 32;
data.pid = pid;
bpf_get_current_comm(&data.comm, sizeof(data.comm));
/*
* The following deals with a kernel version change (in mainline 4.14, although
* it may be backported to earlier kernels) with how the disk name is accessed.
* We handle both pre- and post-change versions here. Please avoid kernel
* version tests like this as much as possible: they inflate the code, test,
* and maintenance burden.
*/
#ifdef bio_dev
struct gendisk *bi_disk = bio->bi_disk;
#else
struct gendisk *bi_disk = bio->bi_bdev->bd_disk;
#endif
bpf_probe_read_kernel(&data.disk, sizeof(data.disk), bi_disk->disk_name);
events.perf_submit(ctx, &data, sizeof(data));
return 0;
}
""")
# header
print("Tracing md flush requests... Hit Ctrl-C to end.")
print("%-8s %-7s %-16s %s" % ("TIME", "PID", "COMM", "DEVICE"))
# process event
def print_event(cpu, data, size):
event = b["events"].event(data)
print("%-8s %-7d %-16s %s" % (strftime("%H:%M:%S"), event.pid,
event.comm.decode('utf-8', 'replace'),
event.disk.decode('utf-8', 'replace')))
# read events
b["events"].open_perf_buffer(print_event)
while 1:
try:
b.perf_buffer_poll()
except KeyboardInterrupt:
exit()
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