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Commit 6959dcf9 authored by mcaleavya's avatar mcaleavya
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Add bitesize tool

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man/man8/bitesize.8 0 → 100644
View file @ 6959dcf9
.TH bitesize 8 "2016-02-05" "USER COMMANDS"
.SH NAME
bitesize \- Summarize block device I/O size as a histogram \- Linux eBPF/bcc.
.SH SYNOPSIS
.B bitesize
.SH DESCRIPTION
Show I/O distribution for requested block sizes, by process name.
This works by tracing block I/O kernel functions using dynamic
tracing and prints a historgram of I/O size.
Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF and bcc.
.SH EXAMPLES
.TP
Count I/O size per process until Ctrl-C is hit:
#
.B bitesize
.SH FIELDS
.TP
Kbtes
Size in kilobytes of range
.TP
count
How many I/O fell into this range
.TP
distribution
An ASCII bar chart to visualize the distribution (count column)
.SH OVERHEAD
This traces kernel block I/O functions to update a histgroam, which are
asynchronously copied to user-space. This method is very efficient, and
the overhead for most storage I/O rates (< 10k IOPS) should be negligible.
If you have a higher IOPS storage environment, test and quantify the overhead
before use.
.SH SOURCE
This is from bcc.
.IP
https://github.com/iovisor/bcc
.PP
Also look in the bcc distribution for a companion _examples.txt file containing
example usage, output, and commentary for this tool.
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHOR
Allan McAleavy
.SH SEE ALSO
https://github.com/brendangregg/systemtap-lwtools/blob/master/disk/bitesize-nd.stp
tools/bitesize.py 0 → 100644
View file @ 6959dcf9
#!/usr/bin/python
#
# bitehist.py Block I/O size histogram.
# For Linux, uses BCC, eBPF. See .c file.
#
# USAGE: bitesize
# Ctrl-C will print the partially gathered histogram then exit.
#
#
# Copyright (c) 2016 Allan McAleavy
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 05-Feb-2016 Allan McAleavy ran pep8 against file
from bcc import BPF
from time import sleep
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/blkdev.h>
struct proc_key_t {
char name[TASK_COMM_LEN];
u64 slot;
};
struct val_t {
char name[TASK_COMM_LEN];
};
BPF_HISTOGRAM(dist, struct proc_key_t);
BPF_HASH(commbyreq, struct request *, struct val_t);
int trace_pid_start(struct pt_regs *ctx, struct request *req)
{
struct val_t val = {};
if (bpf_get_current_comm(&val.name, sizeof(val.name)) == 0) {
commbyreq.update(&req, &val);
}
return 0;
}
int do_count (struct pt_regs *ctx, struct request *req)
{
struct val_t *valp;
valp = commbyreq.lookup(&req);
if ( valp == 0) {
return 0;
}
if (req->__data_len > 0) {
struct proc_key_t key = {.slot = bpf_log2l(req->__data_len / 1024)};
bpf_probe_read(&key.name, sizeof(key.name),valp->name);
dist.increment(key);
}
return 0;
}
"""
# load BPF program
b = BPF(text=bpf_text)
b.attach_kprobe(event="blk_account_io_start", fn_name="trace_pid_start")
b.attach_kprobe(event="blk_account_io_completion", fn_name="do_count")
print("Tracing... Hit Ctrl-C to end.")
# trace until Ctrl-C
dist = b.get_table("dist")
try:
sleep(99999999)
except KeyboardInterrupt:
dist.print_log2_hist("Kbytes", "Process Name:")
tools/bitesize_example.txt 0 → 100644
View file @ 6959dcf9
Example of BCC tool bitesize.py
The aim of this tool is to show I/O distribution for requested block sizes, by process name.
# ./bitesize.py
Tracing... Hit Ctrl-C to end.
^C
Process Name: = 'kworker/u128:1'
Kbytes : count distribution
0 -> 1 : 1 |******************** |
2 -> 3 : 0 | |
4 -> 7 : 2 |****************************************|
Process Name: = 'bitesize.py'
Kbytes : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 1 |****************************************|
Process Name: = 'dd'
Kbytes : count distribution
0 -> 1 : 3 | |
2 -> 3 : 0 | |
4 -> 7 : 6 | |
8 -> 15 : 0 | |
16 -> 31 : 1 | |
32 -> 63 : 1 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 1 | |
512 -> 1023 : 0 | |
1024 -> 2047 : 488 |****************************************|
Process Name: = 'jbd2/dm-1-8'
Kbytes : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 1 |****************************************|
Process Name: = 'cat'
Kbytes : count distribution
0 -> 1 : 1 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 1 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 1924 |****************************************|
Process Name: = 'ntpd'
Kbytes : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 104 |****************************************|
Process Name: = 'vmtoolsd'
Kbytes : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 1 |****************************************|
Process Name: = 'bash'
Kbytes : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 2 |****************************************|
Process Name: = 'jbd2/sdb-8'
Kbytes : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 1 |****************************************|
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 1 |****************************************|
We can see from above that there was a dd command being run which generated 488 IOPS between 1MB and 2MB, we can also see the
cat command generating 1924 IOPS between 256Kb and 512Kb.
See also systemtap version:
https://github.com/brendangregg/systemtap-lwtools/blob/master/disk/bitesize-nd.stp
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