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Commit 5e4e1f46 authored by Sasha Goldshtein's avatar Sasha Goldshtein
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Updated man and examples with new probe syntax and command-line switches

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README.md
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......@@ -65,6 +65,7 @@ Examples:
Tools:
- tools/[argdist](tools/argdist.py): Display function parameter values as a histogram or frequency count. [Examples](tools/argdist_example.txt).
- 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/[biotop](tools/biotop.py): Top for disks: Summarize block device I/O by process. [Examples](tools/biotop_example.txt).
......@@ -79,7 +80,6 @@ Tools:
- tools/[filetop](tools/filetop.py): File reads and writes by filename and process. Top for files. [Examples](tools/filetop_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).
- tools/[gentrace](tools/gentrace.py): Trace function parameter values as a histogram or raw data. [Examples](tools/gentrace_examples.txt).
- tools/[gethostlatency](tools/gethostlatency.py): Show latency for getaddrinfo/gethostbyname[2] calls. [Examples](tools/gethostlatency_example.txt).
- tools/[hardirqs](tools/hardirqs.py): Measure hard IRQ (hard interrupt) event time. [Examples](tools/hardirqs_example.txt).
- tools/[killsnoop](tools/killsnoop.py): Trace signals issued by the kill() syscall. [Examples](tools/killsnoop_example.txt).
......
man/man8/argdist.8
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.TH gentrace 8 "2016-02-11" "USER COMMANDS"
.TH argdist 8 "2016-02-11" "USER COMMANDS"
.SH NAME
gentrace \- Trace a function and display a histogram or summary of its parameter values. Uses Linux eBPF/bcc.
argdist \- Trace a function and display a histogram or frequency count of its parameter values. Uses Linux eBPF/bcc.
.SH SYNOPSIS
.B gentrace [-h] [-p PID] [-z STRING_SIZE] [-i INTERVAL] [-c COUNT] specifier [specifier ...]
.B argdist [-h] [-p PID] [-z STRING_SIZE] [-i INTERVAL] [-n COUNT] [-H specifier [specifier ...]] [-C specifier [specifier ...]]
.SH DESCRIPTION
gentrace attaches to function entry and exit points, collects specified parameter
values, and stores them in a histogram or a raw counting collection that counts
argdist attaches to function entry and exit points, collects specified parameter
values, and stores them in a histogram or a frequency collection that counts
the number of times a parameter value occurred. It can also filter parameter
values and instrument multiple entry points at once.
......@@ -18,8 +18,7 @@ CONFIG_BPF and bcc.
Print usage message.
.TP
\-p PID
Trace only functions in the process PID. This filter will only apply to user-space
functions. If you only provide kernel-space probes, the filter is ignored.
Trace only functions in the process PID.
.TP
\-z STRING_SIZE
When collecting string arguments (of type char*), collect up to STRING_SIZE
......@@ -28,88 +27,98 @@ characters. Longer strings will be truncated.
-i INTERVAL
Print the collected data every INTERVAL seconds. The default is 1 second.
.TP
-c COUNT
-n NUMBER
Print the collected data COUNT times and then exit.
.TP
SPECIFIER
One or more probe specifications that instruct gentrace which functions to
-H SPECIFIER, -C SPECIFIER
One or more probe specifications that instruct argdist which functions to
probe, which parameters to collect, how to aggregate them, and whether to perform
any filtering. See SPECIFIER SYNTAX below.
.SH SPECIFIER SYNTAX
The general specifier syntax is as follows:
.B <raw|hist>[-ret]:[library]:function(signature)[:type:expr[:filter]]
.B {p,r}:[library]:function(signature)[:type:expr[:filter]][;label]
.TP
Probe type \- "raw", "hist", "raw-ret", "hist-ret".
Indicates where to place the probe and whether the probe should collect raw
event information, or aggregate the collected values into a histogram. Raw
.B {p,r}
Probe type \- "p" for function entry, "r" for function return;
\-H for histogram collection, \-C for frequency count.
Indicates where to place the probe and whether the probe should collect frequency
count information, or aggregate the collected values into a histogram. Counting
probes will collect the number of times every parameter value was observed,
whereas histogram probes will collect the parameter values into a histogram.
Only integral types can be used with histogram probes; there is no such limitation
for raw probes. Suffix with \-ret to indicate that the probe should be placed
at function return. This probe can only use the pseudo-variable @retval, which
for counting probes. Return probes can only use the pseudo-variable $retval, which
is an alias for the function's return value.
.TP
.B [library]
Library containing the probe.
Specify the full path to the .so or executable file where the function to probe
resides. Alternatively, you can specify just the lib name: for example, "c"
refers to libc. If no library name is specified, the kernel is assumed.
.TP
.B function(signature)
The function to probe, and its signature.
The function name must match exactly for the probe to be placed. The signature,
on the other hand, is only required if you plan to collect parameter values
based on that signature. For example, if you only want to collect the first
parameter, you don't have to specify the rest of the parameters in the signature.
.TP
.B [type]
The type of the expression to capture.
This is the type of the keys in the histogram or raw event collection that are
collected by the probes.
.TP
.B [expr]
The expression to capture.
These are the values that are assigned to the histogram or raw event collection.
You may use the parameters directly, or valid C expressions that involve the
parameters, such as "size % 10".
.TP
A filter applied to the captured data.
.B [filter]
The filter applied to the captured data.
Only parameter values that pass the filter will be collected. This is any valid
C expression that refers to the parameter values, such as "fd == 1 && length > 16".
.TP
.B [label]
The label that will be displayed when printing the probed values. By default,
this is the probe specifier.
.SH EXAMPLES
.TP
Print a histogram of allocation sizes passed to kmalloc:
#
.B gentrace.py 'hist::__kmalloc(u64 size):u64:size'
.B argdist.py -H 'p::__kmalloc(u64 size):u64:size'
.TP
Print a raw count of how many times process 1005 called malloc with an allocation size of 16 bytes:
Print a count of how many times process 1005 called malloc with an allocation size of 16 bytes:
#
.B gentrace.py -p 1005 'raw:c:malloc(size_t size):size_t:size:size==16'
.B argdist.py -p 1005 -C 'p:c:malloc(size_t size):size_t:size:size==16'
.TP
Snoop on all strings returned by gets():
#
.B gentrace.py 'raw-ret:c:gets():char*:@retval'
.B argdist.py -C 'r:c:gets():char*:$retval'
.TP
Print raw counts of how many times writes were issued to a particular file descriptor number, in process 1005:
Print frequency counts of how many times writes were issued to a particular file descriptor number, in process 1005:
#
.B gentrace.py -p 1005 'raw:c:write(int fd):int:fd'
.B argdist.py -p 1005 -C 'p:c:write(int fd):int:fd'
.TP
Print a histogram of error codes returned by read() in process 1005:
#
.B gentrace.py -p 1005 'hist-ret:c:read()'
.B argdist.py -p 1005 -H 'r:c:read()'
.TP
Print a histogram of buffer sizes passed to write() across all processes, where the file descriptor was 1 (STDOUT):
#
.B gentrace.py 'hist:c:write(int fd, const void *buf, size_t count):size_t:count:fd==1'
.B argdist.py -H 'p:c:write(int fd, const void *buf, size_t count):size_t:count:fd==1'
.TP
Count fork() calls in libc across all processes:
Count fork() calls in libc across all processes, grouped by pid:
#
.B gentrace.py 'raw:c:fork'
.B argdist.py -C 'p:c:fork():int:$PID;fork per process'
.TP
Print histograms of sleep() and nanosleep() parameter values:
#
.B gentrace.py 'hist:c:sleep(u32 seconds):u32:seconds' 'hist:c:nanosleep(struct timespec { time_t tv_sec; long tv_nsec; } *req):long:req->tv_nsec'
.B argdist.py -H 'p:c:sleep(u32 seconds):u32:seconds' -H 'p:c:nanosleep(struct timespec { time_t tv_sec; long tv_nsec; } *req):long:req->tv_nsec'
.TP
Spy on writes to STDOUT performed by process 2780, up to a string size of 120 characters:
#
.B gentrace.py -p 2780 -z 120 'raw:c:write(int fd, char* buf, size_t len):char*:buf:fd==1'
.B argdist.py -p 2780 -z 120 -C 'p:c:write(int fd, char* buf, size_t len):char*:buf:fd==1'
.SH SOURCE
This is from bcc.
.IP
......
tools/argdist.py
View file @ 5e4e1f46
......@@ -28,6 +28,14 @@ int PROBENAME(struct pt_regs *ctx SIGNATURE)
}
"""
next_probe_index = 0
aliases = { "$PID": "bpf_get_current_pid_tgid()" }
def _substitute_aliases(self, expr):
if expr is None:
return expr
for alias, subst in Specifier.aliases.items():
expr = expr.replace(alias, subst)
return expr
def __init__(self, type, specifier, pid):
self.raw_spec = specifier
......@@ -66,6 +74,8 @@ int PROBENAME(struct pt_regs *ctx SIGNATURE)
if self.filter is not None:
self.filter = self.filter.replace("$retval",
"(%s)ctx->ax" % self.expr_type)
self.expr = self._substitute_aliases(self.expr)
self.filter = self._substitute_aliases(self.filter)
self.pid = pid
self.probe_func_name = "%s_probe%d" % \
(self.function, Specifier.next_probe_index)
......
tools/argdist_example.txt → tools/argdist_examples.txt
View file @ 5e4e1f46
Demonstrations of gentrace.
Demonstrations of argdist.
gentrace probes functions you specify and collects parameter values into a
histogram or a counting table. This can be used to understand the distribution
argdist probes functions you specify and collects parameter values into a
histogram or a frequency count. This can be used to understand the distribution
of values a certain parameter takes, filter and print interesting parameters
without attaching a debugger, and getting general execution statistics on
without attaching a debugger, and obtain general execution statistics on
various functions.
For example, suppose you want to find what allocation sizes are common in
your application:
# ./gentrace.py -p 2420 "raw:c:malloc(size_t size):size_t:size"
# ./argdist.py -p 2420 -C 'p:c:malloc(size_t size):size_t:size'
[01:42:29]
raw:c:malloc(size_t size):size_t:size
p:c:malloc(size_t size):size_t:size
COUNT EVENT
[01:42:30]
raw:c:malloc(size_t size):size_t:size
p:c:malloc(size_t size):size_t:size
COUNT EVENT
[01:42:31]
raw:c:malloc(size_t size):size_t:size
p:c:malloc(size_t size):size_t:size
COUNT EVENT
1 size = 16
[01:42:32]
raw:c:malloc(size_t size):size_t:size
p:c:malloc(size_t size):size_t:size
COUNT EVENT
2 size = 16
[01:42:33]
raw:c:malloc(size_t size):size_t:size
p:c:malloc(size_t size):size_t:size
COUNT EVENT
3 size = 16
[01:42:34]
raw:c:malloc(size_t size):size_t:size
p:c:malloc(size_t size):size_t:size
COUNT EVENT
4 size = 16
^C
......@@ -43,9 +43,9 @@ probed and its value was 16, repeatedly.
Now, suppose you wanted a histogram of buffer sizes passed to the write()
function across the system:
# ./gentrace.py "hist:c:write(int fd, void *buf, size_t len):size_t:len"
# ./argdist.py -H 'p:c:write(int fd, void *buf, size_t len):size_t:len'
[01:45:22]
hist:c:write(int fd, void *buf, size_t len):size_t:len
p:c:write(int fd, void *buf, size_t len):size_t:len
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 2 |************* |
......@@ -54,7 +54,7 @@ hist:c:write(int fd, void *buf, size_t len):size_t:len
16 -> 31 : 0 | |
32 -> 63 : 6 |****************************************|
[01:45:23]
hist:c:write(int fd, void *buf, size_t len):size_t:len
p:c:write(int fd, void *buf, size_t len):size_t:len
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 11 |*************** |
......@@ -64,7 +64,7 @@ hist:c:write(int fd, void *buf, size_t len):size_t:len
32 -> 63 : 28 |****************************************|
64 -> 127 : 12 |***************** |
[01:45:24]
hist:c:write(int fd, void *buf, size_t len):size_t:len
p:c:write(int fd, void *buf, size_t len):size_t:len
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 21 |**************** |
......@@ -81,9 +81,9 @@ bytes, medium writes of 32-63 bytes, and larger writes of 64-127 bytes.
But these are writes across the board -- what if you wanted to focus on writes
to STDOUT?
# ./gentrace.py "hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1"
# ./argdist.py -H 'p:c:write(int fd, void *buf, size_t len):size_t:len:fd==1'
[01:47:17]
hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
p:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
......@@ -92,7 +92,7 @@ hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
16 -> 31 : 0 | |
32 -> 63 : 1 |****************************************|
[01:47:18]
hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
p:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
......@@ -102,7 +102,7 @@ hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
32 -> 63 : 3 |******************** |
64 -> 127 : 6 |****************************************|
[01:47:19]
hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
p:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
......@@ -116,20 +116,20 @@ hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
The "fd==1" part is a filter that is applied to every invocation of write().
Only if the filter condition is true, the value is recorded.
You can also use gentrace to trace kernel functions. For example, suppose you
You can also use argdist to trace kernel functions. For example, suppose you
wanted a histogram of kernel allocation (kmalloc) sizes across the system,
printed twice with 3 second intervals:
# ./gentrace.py -i 3 -c 2 "hist::__kmalloc(size_t size):size_t:size"
# ./argdist.py -i 3 -n 2 -H 'p::__kmalloc(size_t size):size_t:size'
[01:50:00]
hist::__kmalloc(size_t size):size_t:size
p::__kmalloc(size_t size):size_t:size
size : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 6 |****************************************|
[01:50:03]
hist::__kmalloc(size_t size):size_t:size
p::__kmalloc(size_t size):size_t:size
size : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
......@@ -143,9 +143,9 @@ hist::__kmalloc(size_t size):size_t:size
Occasionally, numeric information isn't enough and you want to capture strings.
What are the strings printed by puts() across the system?
# ./gentrace.py -i 10 -c 1 "raw:c:puts(char *str):char*:str"
# ./argdist.py -i 10 -n 1 -C 'p:c:puts(char *str):char*:str'
[01:53:54]
raw:c:puts(char *str):char*:str
p:c:puts(char *str):char*:str
COUNT EVENT
2 str = Press ENTER to start.
......@@ -153,22 +153,23 @@ It looks like the message "Press ENTER to start." was printed twice during the
10 seconds we were tracing.
What about reads? You could trace gets() across the system and print the
strings input by the user:
strings input by the user (note how "r" is used instead of "p" to attach a
probe to the function's return):
# ./gentrace.py -i 10 -c 1 "raw-ret:c:gets():char*:@retval"
# ./argdist.py -i 10 -n 1 -C 'r:c:gets():char*:$retval:$retval!=0'
[02:12:23]
raw-ret:c:gets():char*:@retval
r:c:gets():char*:$retval:$retval!=0
COUNT EVENT
1 (char*)ctx->ax = hi there
1 (char*)ctx->ax = sasha
1 (char*)ctx->ax = hello
3 (char*)ctx->ax = sasha
8 (char*)ctx->ax = hello
Similarly, we could get a histogram of the error codes returned by read():
# ./gentrace.py -i 10 -c 1 "hist-ret:c:read()"
# ./argdist.py -i 10 -c 1 -H 'r:c:read()'
[02:15:36]
hist-ret:c:read()
(int)ctx->ax : count distribution
r:c:read()
retval : count distribution
0 -> 1 : 29 |****************************************|
2 -> 3 : 11 |*************** |
4 -> 7 : 0 | |
......@@ -182,18 +183,35 @@ hist-ret:c:read()
1024 -> 2047 : 0 | |
2048 -> 4095 : 2 |** |
Here's a final example that finds how many write() system calls are performed
by each process on the system:
# argdist.py -C 'p:c:write():int:$PID;write per process' -n 2
[06:47:18]
write by process
COUNT EVENT
3 bpf_get_current_pid_tgid() = 8889
7 bpf_get_current_pid_tgid() = 7615
7 bpf_get_current_pid_tgid() = 2480
[06:47:19]
write by process
COUNT EVENT
9 bpf_get_current_pid_tgid() = 8889
23 bpf_get_current_pid_tgid() = 7615
23 bpf_get_current_pid_tgid() = 2480
As you see, the $PID alias is expanded to the BPF function bpf_get_current_pid_tgid(),
which returns the current process' pid.
USAGE message:
# ./gentrace.py -h
usage: gentrace.py [-h] [-p PID] [-z STRING_SIZE] [-i INTERVAL] [-c COUNT]
specifier [specifier ...]
usage: argdist.py [-h] [-p PID] [-z STRING_SIZE] [-i INTERVAL] [-n COUNT]
[-H [HISTSPECIFIER [HISTSPECIFIER ...]]]
[-C [COUNTSPECIFIER [COUNTSPECIFIER ...]]] [-v]
Trace a function and display a summary of its parameter values.
positional arguments:
specifier the probe specifiers (see examples below)
optional arguments:
-h, --help show this help message and exit
-p PID, --pid PID id of the process to trace (optional)
......@@ -201,55 +219,65 @@ optional arguments:
maximum string size to read from char* arguments
-i INTERVAL, --interval INTERVAL
output interval, in seconds
-c COUNT, --count COUNT
-n COUNT, --number COUNT
number of outputs
-H [HISTSPECIFIER [HISTSPECIFIER ...]], --histogram [HISTSPECIFIER [HISTSPECIFIER ...]]
probe specifier to capture histogram of (see examples
below)
-C [COUNTSPECIFIER [COUNTSPECIFIER ...]], --count [COUNTSPECIFIER [COUNTSPECIFIER ...]]
probe specifier to capture count of (see examples
below)
-v, --verbose print resulting BPF program code before executing
Probe specifier syntax:
<raw|hist>[-ret]:[library]:function(signature)[:type:expr[:filter]]
{p,r}:[library]:function(signature)[:type:expr[:filter]][;label]
Where:
<raw|hist> -- collect raw data or a histogram of values
ret -- probe at function exit, only @retval is accessible
p,r -- probe at function entry or at function exit
in exit probes, only $retval is accessible
library -- the library that contains the function
(leave empty for kernel functions)
function -- the function name to trace
signature -- the function's parameters, as in the C header
type -- the type of the expression to collect
expr -- the expression to collect
filter -- a filter that is applied to collected values
filter -- the filter that is applied to collected values
label -- the label for this probe in the resulting output
EXAMPLES:
gentrace.py "hist::__kmalloc(u64 size):u64:size"
argdist.py -H 'p::__kmalloc(u64 size):u64:size'
Print a histogram of allocation sizes passed to kmalloc
gentrace.py -p 1005 "raw:c:malloc(size_t size):size_t:size:size==16"
Print a raw count of how many times process 1005 called malloc with
an allocation size of 16 bytes
argdist.py -p 1005 -C 'p:c:malloc(size_t size):size_t:size:size==16'
Print a frequency count of how many times process 1005 called malloc
with an allocation size of 16 bytes
gentrace.py "raw-ret:c:gets():char*:@retval"
argdist.py -C 'r:c:gets():char*:$retval;snooped strings'
Snoop on all strings returned by gets()
gentrace.py -p 1005 "raw:c:write(int fd):int:fd"
Print raw counts of how many times writes were issued to a particular
file descriptor number, in process 1005
argdist.py -p 1005 -C 'p:c:write(int fd):int:fd'
Print frequency counts of how many times writes were issued to a
particular file descriptor number, in process 1005
gentrace.py -p 1005 "hist-ret:c:read()"
argdist.py -p 1005 -H 'r:c:read()'
Print a histogram of error codes returned by read() in process 1005
gentrace.py "hist:c:write(int fd, const void *buf, size_t count):size_t:count:fd==1"
argdist.py -H \
'p:c:write(int fd, const void *buf, size_t count):size_t:count:fd==1'
Print a histogram of buffer sizes passed to write() across all
processes, where the file descriptor was 1 (STDOUT)
gentrace.py "raw:c:fork"
argdist.py -C 'p:c:fork();fork calls'
Count fork() calls in libc across all processes
Can also use funccount.py, which is easier and more flexible
gentrace.py \
"hist:c:sleep(u32 seconds):u32:seconds" \
"hist:c:nanosleep(struct timespec { time_t tv_sec; long tv_nsec; } *req):long:req->tv_nsec"
argdist.py \
-H 'p:c:sleep(u32 seconds):u32:seconds' \
-H 'p:c:nanosleep(struct timespec { time_t tv_sec; long tv_nsec; } *req):long:req->tv_nsec'
Print histograms of sleep() and nanosleep() parameter values
gentrace.py -p 2780 -z 120 "raw:c:write(int fd, char* buf, size_t len):char*:buf:fd==1"
argdist.py -p 2780 -z 120 \
-C 'p:c:write(int fd, char* buf, size_t len):char*:buf:fd==1'
Spy on writes to STDOUT performed by process 2780, up to a string size
of 120 characters
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