Ok,
Here is a quick introduction to DTrace, with one line scripts. This can be
used as basic troubleshooting to point out problems in max 3 commands :-)
1. Find process asking for system calls (it generates system time):
# *dtrace -n 'syscall:::entry { @[probefunc]=count(); }'*
dtrace: description 'syscall:::entry ' matched 237 probes
^C [wait 10 secs]
[...]
semsys 1140
read 1826
pollsys 3340
ioctl 5398
yield 23179
2. Once you find the system call heavily used, let's see which is the
process is asking for it. As Gerald is interested in the IOs, let's check
the ioctl.
# *dtrace -n 'syscall::ioctl:entry { @[execname,pid]=count();}'
*dtrace: description 'syscall::ioctl:entry ' matched 1 probe
^C [wait 10 secs]
[...]
Xorg 636 404
compiz-bin 715 423
soffice.bin 1057 456
firefox-bin 816 3004
3. OK, it's my firefoy the one doing a lot of IOs. Let's see to which
file/connection.
# *dtrace -n 'syscall::ioctl:entry / pid==816 / { @[arg0]=count();}'
*dtrace: description 'syscall::ioctl:entry ' matched 1 probe
^C
4 2760
4. If you are only interested in the reads/writes, you can monitor them for
a given process:
# *dtrace -n 'syscall::read*:entry,syscall::write*:entry /pid==816/ {
@[probefunc,arg0]=count();} '*
dtrace: description 'syscall::read*:entry,syscall::write*:entry ' matched 5
probes
^C
[...]
write 51 1323
write 4 2832
read 22 3178
write 23 3178
read 54 6483
read 4 6578
# *pfiles 816*
816: /usr/lib/firefox/firefox-bin
Current rlimit: 1024 file descriptors
4: S_IFSOCK mode:0666 dev:324,0 ino:33179 uid:0 gid:0 size:0
O_RDWR|O_NONBLOCK FD_CLOEXEC
SOCK_STREAM
SO_SNDBUF(16384),SO_RCVBUF(5120)
sockname: AF_UNIX
peername: AF_UNIX /tmp/.X11-unix/X0
22: S_IFIFO mode:0000 dev:313,0 ino:606 uid:101 gid:10 size:0
O_RDWR|O_NONBLOCK
23: S_IFIFO mode:0000 dev:313,0 ino:606 uid:101 gid:10 size:0
O_RDWR|O_NONBLOCK
51: S_IFSOCK mode:0666 dev:324,0 ino:50064 uid:0 gid:0 size:0
O_RDWR|O_NONBLOCK
SOCK_STREAM
SO_SNDBUF(49152),SO_RCVBUF(49680)
sockname: AF_INET 192.168.200.167 port: 35980
peername: AF_INET 74.125.39.19 port: 443
54: S_IFSOCK mode:0666 dev:324,0 ino:43204 uid:0 gid:0 size:0
O_RDWR|O_NONBLOCK
SOCK_STREAM
SO_SNDBUF(49152),SO_RCVBUF(49680)
sockname: AF_INET 192.168.200.167 port: 44800
peername: AF_INET 204.152.191.104 port: 80
--> In my case, a part from the usual internal stuff of firefox to draw the
X window, the connection generating the more IOs is a read from
204.152.191.104 (a download from rsync.genunix.org).
Gerald, if you need something more precisely, let me know.
Cheers,
Javi
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