#!/usr/bin/python
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# @lint-avoid-python-3-compatibility-imports
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#
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# mdflush Trace md flush events.
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# For Linux, uses BCC, eBPF.
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#
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# Todo: add more details of the flush (latency, I/O count).
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#
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# Copyright 2016 Netflix, Inc.
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# Licensed under the Apache License, Version 2.0 (the "License")
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#
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# 13-Feb-2015 Brendan Gregg Created this.
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from __future__ import print_function
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from bcc import BPF
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from time import strftime
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import ctypes as ct
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# load BPF program
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b = BPF(text="""
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#include <uapi/linux/ptrace.h>
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#include <linux/sched.h>
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#include <linux/genhd.h>
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#include <linux/bio.h>
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struct data_t {
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u64 pid;
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char comm[TASK_COMM_LEN];
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char disk[DISK_NAME_LEN];
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};
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BPF_PERF_OUTPUT(events);
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int kprobe__md_flush_request(struct pt_regs *ctx, void *mddev, struct bio *bio)
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{
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struct data_t data = {};
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u32 pid = bpf_get_current_pid_tgid();
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data.pid = pid;
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bpf_get_current_comm(&data.comm, sizeof(data.comm));
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/*
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* The following deals with a kernel version change (in mainline 4.14, although
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* it may be backported to earlier kernels) with how the disk name is accessed.
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* We handle both pre- and post-change versions here. Please avoid kernel
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* version tests like this as much as possible: they inflate the code, test,
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* and maintenance burden.
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*/
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#ifdef bio_dev
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struct gendisk *bi_disk = bio->bi_disk;
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#else
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struct gendisk *bi_disk = bio->bi_bdev->bd_disk;
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#endif
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bpf_probe_read(&data.disk, sizeof(data.disk), bi_disk->disk_name);
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events.perf_submit(ctx, &data, sizeof(data));
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return 0;
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}
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""")
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# event data
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TASK_COMM_LEN = 16 # linux/sched.h
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DISK_NAME_LEN = 32 # linux/genhd.h
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class Data(ct.Structure):
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_fields_ = [
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("pid", ct.c_ulonglong),
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("comm", ct.c_char * TASK_COMM_LEN),
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("disk", ct.c_char * DISK_NAME_LEN)
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]
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# header
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print("Tracing md flush requests... Hit Ctrl-C to end.")
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print("%-8s %-6s %-16s %s" % ("TIME", "PID", "COMM", "DEVICE"))
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# process event
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def print_event(cpu, data, size):
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event = ct.cast(data, ct.POINTER(Data)).contents
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print("%-8s %-6d %-16s %s" % (strftime("%H:%M:%S"), event.pid,
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event.comm.decode('utf-8', 'replace'),
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event.disk.decode('utf-8', 'replace')))
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# read events
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b["events"].open_perf_buffer(print_event)
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while 1:
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b.perf_buffer_poll()
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