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filetop_example.txt
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filetop_example.txt
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Demonstrations of filetop, the Linux eBPF/bcc version.
filetop shows reads and writes by file, with process details. For example:
# ./filetop -C
Tracing... Output every 1 secs. Hit Ctrl-C to end
08:00:23 loadavg: 0.91 0.33 0.23 3/286 26635
PID COMM READS WRITES R_Kb W_Kb T FILE
26628 ld 161 186 643 152 R built-in.o
26634 cc1 1 0 200 0 R autoconf.h
26618 cc1 1 0 200 0 R autoconf.h
26634 cc1 12 0 192 0 R tracepoint.h
26584 cc1 2 0 143 0 R mm.h
26634 cc1 2 0 143 0 R mm.h
26631 make 34 0 136 0 R auto.conf
26634 cc1 1 0 98 0 R fs.h
26584 cc1 1 0 98 0 R fs.h
26634 cc1 1 0 91 0 R sched.h
26634 cc1 1 0 78 0 R printk.c
26634 cc1 3 0 73 0 R mmzone.h
26628 ld 18 0 72 0 R hibernate.o
26628 ld 16 0 64 0 R suspend.o
26628 ld 16 0 64 0 R snapshot.o
26630 cat 1 0 64 0 O null
26628 ld 16 0 64 0 R qos.o
26628 ld 13 0 52 0 R main.o
26628 ld 12 0 52 0 R swap.o
12421 sshd 3 0 48 0 O ptmx
[...]
This shows various files read and written during a Linux kernel build. The
output is sorted by the total read size in Kbytes (R_Kb). This is instrumenting
at the VFS interface, so this is reads and writes that may return entirely
from the file system cache (page cache).
While not printed, the average read and write size can be calculated by
dividing R_Kb by READS, and the same for writes.
The "T" column indicates the type of the file: "R" for regular files, "S" for
sockets, and "O" for other (including pipes).
This script works by tracing the vfs_read() and vfs_write() functions using
kernel dynamic tracing, which instruments explicit read and write calls. If
files are read or written using another means (eg, via mmap()), then they
will not be visible using this tool.
This should be useful for file system workload characterization when analyzing
the performance of applications.
Note that tracing VFS level reads and writes can be a frequent activity, and
this tool can begin to cost measurable overhead at high I/O rates.
A -C option will stop clearing the screen, and -r with a number will restrict
the output to that many rows (20 by default). For example, not clearing
the screen and showing the top 5 only:
# ./filetop -Cr 5
Tracing... Output every 1 secs. Hit Ctrl-C to end
08:05:11 loadavg: 0.75 0.35 0.25 3/285 822
PID COMM READS WRITES R_Kb W_Kb T FILE
32672 cksum 5006 0 320384 0 R data1
12296 sshd 2 0 32 0 O ptmx
809 run 2 0 8 0 R nsswitch.conf
811 run 2 0 8 0 R nsswitch.conf
804 chown 2 0 8 0 R nsswitch.conf
08:05:12 loadavg: 0.75 0.35 0.25 3/285 845
PID COMM READS WRITES R_Kb W_Kb T FILE
32672 cksum 4986 0 319104 0 R data1
845 chown 2 0 8 0 R nsswitch.conf
828 run 2 0 8 0 R nsswitch.conf
835 run 2 0 8 0 R nsswitch.conf
830 run 2 0 8 0 R nsswitch.conf
08:05:13 loadavg: 0.75 0.35 0.25 3/285 868
PID COMM READS WRITES R_Kb W_Kb T FILE
32672 cksum 4985 0 319040 0 R data1
857 run 2 0 8 0 R nsswitch.conf
858 run 2 0 8 0 R nsswitch.conf
859 run 2 0 8 0 R nsswitch.conf
848 run 2 0 8 0 R nsswitch.conf
[...]
This output shows a cksum command reading data1. Note that
An optional interval and optional count can also be added to the end of the
command line. For example, for 1 second interval, and 3 summaries in total:
# ./filetop -Cr 5 1 3
Tracing... Output every 1 secs. Hit Ctrl-C to end
08:08:20 loadavg: 0.30 0.42 0.31 3/282 5187
PID COMM READS WRITES R_Kb W_Kb T FILE
12421 sshd 14101 0 225616 0 O ptmx
12296 sshd 4 0 64 0 O ptmx
12421 sshd 3 14104 48 778 S TCP
5178 run 2 0 8 0 R nsswitch.conf
5165 run 2 0 8 0 R nsswitch.conf
08:08:21 loadavg: 0.30 0.42 0.31 5/282 5210
PID COMM READS WRITES R_Kb W_Kb T FILE
12421 sshd 9159 0 146544 0 O ptmx
12421 sshd 3 9161 48 534 S TCP
12296 sshd 1 0 16 0 S TCP
5188 run 2 0 8 0 R nsswitch.conf
5203 run 2 0 8 0 R nsswitch.conf
08:08:22 loadavg: 0.30 0.42 0.31 2/282 5233
PID COMM READS WRITES R_Kb W_Kb T FILE
12421 sshd 26166 0 418656 0 O ptmx
12421 sshd 4 26171 64 1385 S TCP
12296 sshd 1 0 16 0 O ptmx
5214 run 2 0 8 0 R nsswitch.conf
5227 run 2 0 8 0 R nsswitch.conf
Detaching...
This example has caught heavy socket I/O from an sshd process, showing up as
non-regular file types (the "O" for other, and "S" for socket, in the type
column: "T").
USAGE message:
# ./filetop -h
usage: filetop [-h] [-C] [-r MAXROWS] [-p PID] [interval] [count]
File reads and writes by process
positional arguments:
interval output interval, in seconds
count number of outputs
optional arguments:
-h, --help show this help message and exit
-C, --noclear don't clear the screen
-r MAXROWS, --maxrows MAXROWS
maximum rows to print, default 20
-p PID, --pid PID trace this PID only
examples:
./filetop # file I/O top, 1 second refresh
./filetop -C # don't clear the screen
./filetop -p 181 # PID 181 only
./filetop 5 # 5 second summaries
./filetop 5 10 # 5 second summaries, 10 times only