Commit 75d3e9d4 authored by Brendan Gregg's avatar Brendan Gregg

rename fsslower to fileslower

parent 1f1c8f80
......@@ -72,7 +72,7 @@ Tools:
- 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/[execsnoop](tools/execsnoop.py): Trace new processes via exec() syscalls. [Examples](tools/execsnoop_example.txt).
- tools/[fsslower](tools/fsslower.py): Trace slow file system synchronous reads and writes. [Examples](tools/fsslower_example.txt).
- tools/[fileslower](tools/fileslower.py): Trace slow synchronous file reads and writes. [Examples](tools/fileslower_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/[gethostlatency](tools/gethostlatency.py): Show latency for getaddrinfo/gethostbyname[2] calls. [Examples](tools/gethostlatency_example.txt).
......
.TH fsslower 8 "2016-02-07" "USER COMMANDS"
.TH fileslower 8 "2016-02-07" "USER COMMANDS"
.SH NAME
fsslower \- Summarize block device I/O latency as a histogram.
fileslower \- Trace slow synchronous file reads and writes.
.SH SYNOPSIS
.B fsslower [\-h] [\-p PID] [min_ms]
.B fileslower [\-h] [\-p PID] [min_ms]
.SH DESCRIPTION
This script uses kernel dynamic tracing of synchronous reads and writes
at the VFS interface, to identify slow file system I/O for any file system.
at the VFS interface, to identify slow file reads and writes for any file
system.
This version traces __vfs_read() and __vfs_write() and only showing
synchronous I/O (the path to new_sync_read() and new_sync_write()), and
I/O with filenames. This approach provides a view of just two file
system request types: reads and writes. There are typically many others:
system request types: file reads and writes. There are typically many others:
asynchronous I/O, directory operations, file handle operations, file open()s,
fflush(), etc, that this tool does not currently instrument. This
implementation is a work around until we have suitable fs tracepoints.
fflush(), etc.
WARNING: See the OVERHEAD section.
......@@ -34,17 +34,17 @@ min_ms
Minimum I/O latency (duration) to trace, in milliseconds. Default is 10 ms.
.SH EXAMPLES
.TP
Trace synchronous file system reads and writes slower than 10 ms:
Trace synchronous file reads and writes slower than 10 ms:
#
.B fsslower
.B fileslower
.TP
Trace slower than 1 ms:
#
.B fsslower 1
.B fileslower 1
.TP
Trace slower than 1 ms, for PID 181 only:
#
.B fsslower \-p 181 1
.B fileslower \-p 181 1
.SH FIELDS
.TP
TIME(s)
......@@ -86,13 +86,13 @@ instrumented events using the bcc funccount tool, eg:
.PP
# ./funccount.py -i 1 -r '^__vfs_(read|write)$'
.PP
This also costs overhead, but is somewhat less than fsslower.
This also costs overhead, but is somewhat less than fileslower.
.PP
If the overhead is prohibitive for your workload, I'd recommend moving
down-stack a little from VFS into the file system functions (ext4, xfs, etc).
Look for updates to bcc for specific file system tools that do this. The
advantage of a per-file system approach is that we can trace post-cache,
greatly reducing events and overhead. The disadvantage is needing custom
greatly reducing events and overhead. The disadvantage is needing custom
tracing approaches for each different file system (whereas VFS is generic).
.SH SOURCE
This is from bcc.
......
#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# fsslower Trace slow file system synchronous reads and writes.
# For Linux, uses BCC, eBPF.
# fileslower Trace slow synchronous file reads and writes.
# For Linux, uses BCC, eBPF.
#
# USAGE: fsslower [-h] [-p PID] [min_ms]
# USAGE: fileslower [-h] [-p PID] [min_ms]
#
# This script uses kernel dynamic tracing of synchronous reads and writes
# at the VFS interface, to identify slow file system I/O for any file system.
# at the VFS interface, to identify slow file reads and writes for any file
# system.
#
# This works by tracing __vfs_read() and __vfs_write(), and filtering for
# synchronous I/O (the path to new_sync_read() and new_sync_write()), and
# for I/O with filenames. This approach provides a view of just two file
# system request types. There are typically many others: asynchronous I/O,
# directory operations, file handle operations, etc, that this tool does not
# instrument. This implementation is a work around until we have suitable fs
# tracepoints.
# instrument.
#
# WARNING: This traces VFS reads and writes, which can be extremely frequent,
# and so the overhead of this tool can become severe depending on the
......@@ -35,12 +35,12 @@ import signal
# arguments
examples = """examples:
./fsslower # trace sync I/O slower than 10 ms (default)
./fsslower 1 # trace sync I/O slower than 1 ms
./fsslower -p 185 # trace PID 185 only
./fileslower # trace sync file I/O slower than 10 ms (default)
./fileslower 1 # trace sync file I/O slower than 1 ms
./fileslower -p 185 # trace PID 185 only
"""
parser = argparse.ArgumentParser(
description="Trace slow file system sync reads and writes",
description="Trace slow synchronous file reads and writes",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-p", "--pid",
......
Demonstrations of fsslower, the Linux eBPF/bcc version.
Demonstrations of fileslower, the Linux eBPF/bcc version.
fsslower shows file-based synchronous reads and writes slower than a threshold.
For example:
fileslower shows file-based synchronous reads and writes slower than a
threshold. For example:
# ./fsslower
# ./fileslower
Tracing sync read/writes slower than 10 ms
TIME(s) COMM PID D BYTES LAT(ms) FILENAME
0.000 randread.pl 4762 R 8192 12.70 data1
......@@ -20,13 +20,13 @@ I/O), file system CPU cycles, file system locks, run queue latency, etc. This
is a better measure of the latency suffered by applications reading from the
file system than measuring this down at the block device interface.
Note that this only traces reads and writes: other file system operations
(eg, directory operations, open(), fflush()) are not currently traced.
Note that this only traces file reads and writes: other file system operations
(eg, directory operations, open(), fflush()) are not traced.
The threshold can be provided as an argument. Eg, I/O slower than 1 ms:
# ./fsslower 1
# ./fileslower 1
Tracing sync read/writes slower than 1 ms
TIME(s) COMM PID D BYTES LAT(ms) FILENAME
0.000 randread.pl 6925 R 8192 1.06 data1
......@@ -62,10 +62,10 @@ spanned 12 seconds), and the lower threshold is catching more I/O.
In the following example, the file system caches were dropped before running
fsslower, and then in another session a "man ls" was executed. The command
fileslower, and then in another session a "man ls" was executed. The command
and files read from disk can be seen:
# echo 3 > /proc/sys/vm/drop_caches; ./fsslower 1
# echo 3 > /proc/sys/vm/drop_caches; ./fileslower 1
Tracing sync read/writes slower than 1 ms
TIME(s) COMM PID D BYTES LAT(ms) FILENAME
0.000 bash 9647 R 128 5.83 man
......@@ -104,10 +104,10 @@ locks, run queue latency, etc. These can be explored using other commands.
USAGE message:
# ./fsslower -h
usage: fsslower [-h] [-p PID] [min_ms]
# ./fileslower -h
usage: fileslower [-h] [-p PID] [min_ms]
Trace slow file system sync reads and writes
Trace slow synchronous file reads and writes
positional arguments:
min_ms minimum I/O duration to trace, in ms (default 10)
......@@ -117,6 +117,6 @@ optional arguments:
-p PID, --pid PID trace this PID only
examples:
./fsslower # trace sync I/O slower than 10 ms (default)
./fsslower 1 # trace sync I/O slower than 1 ms
./fsslower -p 185 # trace PID 185 only
./fileslower # trace sync file I/O slower than 10 ms (default)
./fileslower 1 # trace sync file I/O slower than 1 ms
./fileslower -p 185 # trace PID 185 only
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