This repository contains various scripts to extract monitoring data and metrics from LTTng kernel traces.
This README only describes the usage for iotop.py, but the procedure is pretty-much the same for the other scripts.
iotop.py displays the I/O usage in the trace, per-disk, per-network interface,
per-FD and per-process. It tracks the number of bytes and requests performed
and the latency of the I/O syscalls and block devices.
The user can specify a threshold to see the requests that took more than a
certain time to complete, this extracts the timestamp begin and end of the
requests, so it is then easier to dig into the trace and understand why this
latency happened. It is also possible to see all the I/O requests performed by
a list of processes (see --name parameter).
- LTTng 2.5
- Babeltrace 1.2 (with python bindings compiled)
- Python 3.4+
apt-get install -y software-properties-common (or python-software-properties on 12.04)
apt-add-repository -y ppa:lttng/ppa
apt-get update
apt-get -y install lttng-tools babeltrace lttng-modules-dkms python3-babeltrace python3-progressbar
(If your user is part of the tracing group, you can avoid needing to be root next, after a fresh install it requires to logout and login)
lttng create
lttng enable-channel -k bla --subbuf-size=4M
lttng enable-event -k sched_switch,block_rq_complete,block_rq_issue,block_bio_remap,block_bio_backmerge,netif_receive_skb,net_dev_xmit,sched_process_fork,sched_process_exec,lttng_statedump_process_state,lttng_statedump_file_descriptor,lttng_statedump_block_device,writeback_pages_written,mm_vmscan_wakeup_kswapd,mm_page_free,mm_page_alloc,block_dirty_buffer -c bla
lttng enable-event -k --syscall -a -c bla
lttng start
..do stuff...
lttng stop
lttng destroy
You can also create a trace on a server and send it to a remote host. The
remote host only need to run lttng-relayd -d and be reachable by network.
The only difference with the above commands is the trace session creation :
lttng create -U net://<remote-host>
Once you have collected your trace, you can run iotop.py on it. In this example, we want to extract all the I/O requests that took more than 50ms to complete and also display the general statistics. The use-case in this example is concurrent read and writes in a postgresql database. Here is some extracts from the output of the script :
./iotop.py --no-progress --latency 50 /home/julien/lttng-traces/reddit-postgres01/pgread-writes/kernel/
[16:36:02.916132296 - 16:36:02.994389303] postgres (1348) syscall_entry_recvfrom(fd = 9 <socket:[8893]>, count = 5) = 5, 78.257 ms
[16:36:03.007633298 - 16:36:03.091402482] postgres (1348) syscall_entry_recvfrom(fd = 9 <socket:[8893]>, count = 5) = 5, 83.769 ms
[16:36:03.107392794 - 16:36:03.200894697] postgres (1348) syscall_entry_recvfrom(fd = 9 <socket:[8893]>, count = 5) = 5, 93.502 ms
[...]
[16:36:09.580490482 - 16:36:09.897385130] postgres (4219) syscall_entry_recvfrom(fd = 9 <socket>, count = 5) = 5, 316.895 ms
2715 pages allocated during the period
[16:36:09.614727970 - 16:36:09.914140692] postgres (4220) syscall_entry_recvfrom(fd = 9 <socket>, count = 5) = 5, 299.413 ms
2396 pages allocated during the period
[16:36:09.750251458 - 16:36:09.950608296] postgres (4224) syscall_entry_recvfrom(fd = 9 <socket>, count = 5) = 5, 200.357 ms
904 pages allocated during the period
[...]
[16:36:06.783206662 - 16:36:11.748147198] postgres (1348) syscall_entry_recvfrom(fd = 9 <socket:[8893]>, count = 5) = 5, 4964.941 ms
3541 pages allocated during the period
Tue Oct 7 16:36:00 2014 to Tue Oct 7 16:36:18 2014
Syscall I/O Read
################################################################################################################################################
██████████████████████████████████████████████████ 16777220 16.0 MB lttng-consumerd (2619), 0 B disk, 4.0 B net, 0 B block, 16.0 MB unknown
█████ 1804880 1.72 MB lttng-consumerd (2623), 0 B disk, 0 B net, 0 B block, 1.72 MB unknown
█ 407686 398.13 KB postgres (4219), 121.05 KB disk, 277.07 KB net, 0 B block, 8.0 B unknown
262235 256.09 KB postgres (1348), 0 B disk, 255.97 KB net, 0 B block, 117.0 B unknown
209730 204.81 KB postgres (4218), 204.81 KB disk, 0 B net, 0 B block, 0 B unknown
126737 123.77 KB postgres (4220), 117.5 KB disk, 6.26 KB net, 0 B block, 8.0 B unknown
124579 121.66 KB postgres (4226), 117.5 KB disk, 4.15 KB net, 0 B block, 8.0 B unknown
124189 121.28 KB postgres (4221), 117.5 KB disk, 3.77 KB net, 0 B block, 8.0 B unknown
124125 121.22 KB postgres (4222), 117.5 KB disk, 3.71 KB net, 0 B block, 8.0 B unknown
124125 121.22 KB postgres (4224), 117.5 KB disk, 3.71 KB net, 0 B block, 8.0 B unknown
Syscall I/O Write
###################################################################################################################################################
██████████████████████████████████████████████████ 16777336 16.0 MB lttng-consumerd (2619), 0 B disk, 8.0 MB net, 0 B block, 8.0 MB unknown
██████ 2304240 2.2 MB postgres (4219), 2.0 MB disk, 202.23 KB net, 1.76 MB block, 0 B unknown
█████ 1812800 1.73 MB lttng-consumerd (2623), 0 B disk, 887.73 KB net, 0 B block, 882.58 KB unknown
██ 743760 726.33 KB postgres (1165), 8.0 KB disk, 6.33 KB net, 0 B block, 712.0 KB unknown
162500 158.69 KB postgres (1168), 158.69 KB disk, 0 B net, 160.0 KB block, 0 B unknown
82592 80.66 KB postgres (1348), 0 B disk, 80.66 KB net, 0 B block, 0 B unknown
40960 40.0 KB postgres (1166), 0 B disk, 0 B net, 40.0 KB block, 40.0 KB unknown
13156 12.85 KB lttng (4227), 12.85 KB disk, 0 B net, 0 B block, 0 B unknown
12256 11.97 KB postgres (4220), 2.0 B disk, 11.97 KB net, 0 B block, 0 B unknown
10450 10.21 KB postgres (4226), 2.0 B disk, 10.2 KB net, 0 B block, 0 B unknown
Block I/O Read
###############################################################################
0 0 B init (1)
0 0 B kthreadd (2)
0 0 B ksoftirqd/0 (3)
0 0 B kworker/0:0 (4)
0 0 B kworker/0:0H (5)
0 0 B rcu_sched (7)
0 0 B rcuos/0 (8)
0 0 B rcuos/1 (9)
0 0 B rcuos/2 (10)
0 0 B rcuos/3 (11)
Block I/O Write
#########################################################################################
██████████████████████████████████████████████████ 1843200 1.76 MB postgres (4219)
████ 163840 160.0 KB postgres (1168)
██ 102400 100.0 KB kworker/u8:0 (1540)
██ 98304 96.0 KB jbd2/vda1-8 (257)
█ 40960 40.0 KB postgres (1166)
8192 8.0 KB kworker/u9:0 (4197)
4096 4.0 KB kworker/u9:2 (1381)
0 0 B init (1)
0 0 B kthreadd (2)
0 0 B ksoftirqd/0 (3)
Files Read
##########################################################################################################################
██████████████████████████████████████████████████ 9289728 anon_inode:[lttng_stream] (lttng-consumerd) 8.86 MB (31 2619)
█████████████████████████████████████████████ 8388608 pipe:[53306] (lttng-consumerd) 8.0 MB (11 2619)
████ 903760 pipe:[53309] (lttng-consumerd) 882.58 KB (17 2619)
█ 325340 socket (postgres) 317.71 KB (9 4219)
█ 262235 socket:[8893] (postgres) 256.09 KB (9 1348)
76600 socket:[10713] (postgres) 74.8 KB (8 4218)
52 /dev/ptmx 52.0 B (17 1)
48 socket:[54589] (sshd) 48.0 B (3 3329)
32 /root/trace2.sh 32.0 B (255 4211)
1 /dev/pts/1 1.0 B (0 4211)
Files Write
###########################################################################################################################
██████████████████████████████████████████████████ 9289728 anon_inode:[lttng_stream] (lttng-consumerd) 8.86 MB (31 2619)
█████████████████████████████████████████████ 8388608 pipe:[53306] (lttng-consumerd) 8.0 MB (11 2619)
████ 903760 pipe:[53309] (lttng-consumerd) 882.58 KB (17 2619)
█ 325340 socket (postgres) 317.71 KB (9 4219)
█ 262235 socket:[8893] (postgres) 256.09 KB (9 1348)
76600 socket:[10713] (postgres) 74.8 KB (8 4218)
65536 /var/lib/postgresql/9.1/main/base/16384/16611 64.0 KB (9 1165)
52 /dev/ptmx 52.0 B (17 1)
48 socket:[54589] (sshd) 48.0 B (3 3329)
32 /root/trace2.sh 32.0 B (255 4211)
1 /dev/pts/1 1.0 B (0 4211)
Disk nr_sector
###############################################################################
███████████████████████████████████████████████████████████████████ 4416 vda1
Disk nr_requests
###############################################################################
████████████████████████████████████████████████████████████████████ 177 vda1
Disk request time/sector
###############################################################################
███████████████████████████████████████████████████████████████ 0.014 ms vda1
0.0 ms 0
Network recv_bytes
###############################################################################
████████████████████████████████████████████████████████ 757250 739.5 KB eth0
██████ 82200 80.27 KB lo
Network sent_bytes
###############################################################################
████████████████████████████████████████████████████████ 9811620 9.36 MB eth0
85000 83.01 KB lo
trace2.sh requests latency (ms)
####################################################################################
██████████████████████████████████████████████████ 18011.544456 16:36:00.788362068
postgres requests latency (ms)
###################################################################################
78.257007 16:36:02.916132296
83.769184 16:36:03.007633298
93.501903 16:36:03.107392794
[...]
███ 316.894648 16:36:09.580490482
███ 299.412722 16:36:09.614727970
██ 200.356838 16:36:09.750251458
[...]
██████████████████████████████████████████████████ 4964.940536 16:36:06.783206662
Track the page cache and extract the latencies associated with pages flush to disk. In order to do that, we rely on the assumption that the pages are flushed in a FIFO order. It might not be 100% accurate, but it already gives great results :
An example here when saving a file in vim:
[19:57:51.173332284 - 19:57:51.177794657] vim (31517) syscall_entry_fsync(fd = 4 <blabla>) = 0, 4.462 ms
1 dirty page(s) were flushed (assuming FIFO):
vim (31517): 1 pages
- blabla : 1 pages
13 active dirty filesystem page(s) (known):
redis-server (2092): 2 pages
- /var/log/redis/redis-server.log : 2 pages
vim (31517): 2 pages
- .blabla.swp : 2 pages
lttng-consumerd (6750): 9 pages
- unknown (origin not found) : 9 pages
An other example when running the 'sync' command:
[19:57:53.046840755 - 19:57:53.072809609] sync (31554) syscall_entry_sync(fd = <unknown>) = 0, 25.969 ms
23 dirty page(s) were flushed (assuming FIFO):
redis-server (2092): 2 pages
- /var/log/redis/redis-server.log : 2 pages
vim (31517): 9 pages
- /home/julien/.viminfo.tmp : 6 pages
- .blabla.swp : 3 pages
lttng-consumerd (6750): 12 pages
- unknown (origin not found) : 12 pages
Postgresql with 'sys_fdatasync':
[13:49:39.908599447 - 13:49:39.915930730] postgres (1137) sys_fdatasync(fd = 7 </var/lib/postgresql/9.1/main/pg_xlog/000000010000000000000008>) = 0, 7.331 ms
2 pages allocated during the period
88 dirty page(s) were flushed (assuming FIFO):
postgres (1137): 88 pages
- /var/lib/postgresql/9.1/main/pg_xlog/000000010000000000000008 : 88 pages
68 last dirtied filesystem page(s):
postgres (2419): 68 pages
- base/11951/18410 : 46 pages
- base/11951/18407 : 10 pages
- base/11951/18407_fsm : 6 pages
- base/11951/18410_fsm : 6 pages
Detecting a fight for the I/O between a huge write and postgresql:
[13:49:47.242730583 - 13:49:47.442835037] python (2353) sys_write(fd = 3 </root/bla>, count = 102395904) = 102395904, 200.104 ms
34760 pages allocated during the period
woke up kswapd during the period
10046 pages written on disk
freed 33753 pages from the cache during the period
1397 last dirtied filesystem page(s):
python (2353): 1325 pages
- /root/bla : 1325 pages
postgres (2419): 72 pages
- base/11951/18419 : 72 pages
Hope you have fun trying it and please remember it is a work in progress, feedbacks, bug reports and ideas are alway welcome !
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