Merge pull request #342 from mcaleavya/master

Add in tool bitesize

README.md

@@ -68,6 +68,7 @@ Tools:
 - tools/[bashreadline](tools/bashreadline.py): Print entered bash commands system wide. [Examples](tools/bashreadline_example.txt).
 - tools/[biolatency](tools/biolatency.py): Summarize block device I/O latency as a histogram. [Examples](tools/biolatency_example.txt).
 - tools/[biosnoop](tools/biosnoop.py): Trace block device I/O with PID and latency. [Examples](tools/biosnoop_example.txt).
+- tools/[bitesize](tools/bitesize.py): Show per process I/O size histogram. [Examples](tools/bitesize_example.txt).
 - tools/[cachestat](tools/cachestat.py): Trace page cache hit/miss ratio. [Examples](tools/cachestat_example.txt).
 - tools/[funccount](tools/funccount.py): Count kernel function calls. [Examples](tools/funccount_example.txt).
 - tools/[funclatency](tools/funclatency.py): Time kernel functions and show their latency distribution. [Examples](tools/funclatency_example.txt).

man/man8/bitesize.8

+.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

+#!/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

+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