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SubjectRe: scheduler starvation running irman with 2.5.64bk2
From
> OK, can you do the following to determine whether we're both seeing the
> _same_ problem?

> 1.) build the attached rtnice utility (don't remember who wrote/posted this)
> 2.) login on vt1 and set the shell SCHED_RR via rtnice -n 1 -p <pid_of_sh>
> -d RR
> 3.) login on vt2 and renice that shell to -10
> 4.) login on another vt as a normal user, and start irman
> 5.) try login/out on another vt, or ps or _whatever_ (doesn't matter)
> until box is starving
> 6.) on vt2, try to do ps (it should hang despite -10 priority)
> 7.) on vt1, try to do ps (it should work just fine)

Here is the test as I understand it, splitted by tty. Quick summary,
only new process seems starved. RR and nice -10 process behave okay.

BTW, this is now with 2.5.64bk5.

Below shows irman started, and it gets into the PROCESS
load. Only thing odd here is the PROCESS load never completes.
(or I am not patient enough)

root@mountain:/usr/src/sources/i/irman# tty
/dev/pts/0
root@mountain:/usr/src/sources/i/irman# ./irman
Response time measurements (milliseconds) for: 2.5.64bk5
Load Max Min Avg Std. Dev.
NULL 0.177 0.022 0.026 0.003
MEMORY 1074.825 0.020 0.044 1.424
FILE_IO 408.013 0.016 0.039 2.469


This is the RR shell. It functions okay throughout the
irman run.

root@mountain:~# tty
/dev/pts/1
root@mountain:~# rtnice -n 1 -p $$ -d RR
root@mountain:~# uptime
18:46:33 up 8 min, 3 users, load average: 3.21, 2.06, 0.89


This is the nice -10 shell. It does okay too.

root@mountain:~# tty
/dev/pts/2
root@mountain:~# renice -10 $$
787: old priority 0, new priority -10
root@mountain:~# uptime
18:45:18 up 7 min, 3 users, load average: 3.39, 1.76, 0.70
root@mountain:~# uptime
18:50:19 up 12 min, 3 users, load average: 3.88, 2.98, 1.50
root@mountain:~# ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.5 0.0 1312 100 ? S 18:37 0:04 init [3]
root 2 0.0 0.0 0 0 ? SWN 18:37 0:00 [ksoftirqd/0]
root 3 0.0 0.0 0 0 ? SW< 18:37 0:00 [events/0]
root 4 0.0 0.0 0 0 ? SW 18:37 0:00 [pdflush]
root 5 0.0 0.0 0 0 ? SW 18:37 0:00 [pdflush]
root 6 0.2 0.0 0 0 ? SW 18:37 0:02 [kswapd0]
root 7 0.0 0.0 0 0 ? SW< 18:37 0:00 [aio/0]
root 326 0.0 0.0 0 0 ? SW 18:37 0:00 [eth0]
root 396 0.0 0.0 1368 92 ? S 18:37 0:00 syslogd -m 0
root 401 0.0 0.0 1300 48 ? S 18:37 0:00 klogd -x
rpc 421 0.0 0.0 1444 40 ? S 18:37 0:00 portmap
root 534 0.0 0.0 2568 224 ? S 18:37 0:00 /usr/sbin/sshd
root 544 0.0 0.0 1284 44 tty1 S 18:37 0:00 /sbin/mingetty tty1
root 545 0.0 0.0 1300 44 ttyS1 S 18:37 0:00 /sbin/agetty -h ttyS1 38400 linux
root 548 0.0 0.0 3352 256 ? S 18:38 0:00 /usr/sbin/sshd
rwhron 549 0.0 0.0 2404 32 pts/0 S 18:38 0:00 -bash
root 593 0.0 0.0 2268 48 pts/0 S 18:38 0:00 su -
root 594 0.0 0.0 2400 32 pts/0 S 18:38 0:00 -bash
root 645 0.0 0.0 3352 300 ? S 18:38 0:00 /usr/sbin/sshd
rwhron 646 0.0 0.0 2404 32 pts/1 S 18:38 0:00 -bash
root 690 0.0 0.0 2268 48 pts/1 S 18:38 0:00 su -
root 691 0.0 0.1 2400 512 pts/1 S 18:38 0:00 -bash
root 741 0.0 0.0 3352 300 ? S 18:38 0:00 /usr/sbin/sshd
rwhron 742 0.0 0.0 2404 32 pts/2 S 18:38 0:00 -bash
root 786 0.0 0.0 2268 48 pts/2 S 18:38 0:00 su -
root 787 0.0 0.1 2400 520 pts/2 S< 18:38 0:00 -bash
root 844 23.0 0.0 1460 224 pts/0 R 18:41 2:10 ./irman
root 845 0.0 0.0 0 0 pts/0 Z 18:41 0:00 [irman <defunct>]
root 846 2.1 0.0 0 0 pts/0 Z 18:41 0:12 [irman <defunct>]
root 848 5.9 0.0 0 0 pts/0 Z 18:41 0:32 [mem_load <defunct>]
root 849 2.3 0.0 0 0 pts/0 Z 18:41 0:12 [irman <defunct>]
root 850 0.0 0.0 0 0 pts/0 Z 18:43 0:00 [io_load <defunct>]
root 851 1.7 0.0 0 0 pts/0 Z 18:43 0:07 [irman <defunct>]
root 855 8.9 0.0 1300 324 pts/0 S 18:44 0:32 process_load --processes 10 --recordsize 10000 --injections 2
root 857 7.4 0.0 1288 276 pts/0 S 18:44 0:27 child_process 10000 0 10
root 858 7.9 0.0 1288 276 pts/0 S 18:44 0:28 child_process 10000 3 12
root 859 13.0 0.0 1288 276 pts/0 R 18:44 0:47 child_process 10000 11 14
root 860 13.4 0.0 1288 276 pts/0 S 18:44 0:49 child_process 10000 13 16
root 861 8.0 0.0 1288 276 pts/0 R 18:44 0:29 child_process 10000 15 18
root 862 10.5 0.0 1288 276 pts/0 S 18:44 0:38 child_process 10000 17 20
root 863 11.2 0.0 1288 276 pts/0 S 18:44 0:41 child_process 10000 19 22
root 864 8.7 0.0 1288 276 pts/0 S 18:44 0:31 child_process 10000 21 24
root 865 7.9 0.0 1288 276 pts/0 S 18:44 0:28 child_process 10000 23 26
root 868 0.0 0.0 2568 108 ? R 18:47 0:00 /usr/sbin/sshd
root 874 0.0 0.1 2544 668 pts/2 R< 18:50 0:00 ps aux


However if I start a new connection, it never gives a prompt.


rwhron@rushmore:~$ ssh mt
.. wait several minutes ... still no prompt.


From the RR shell, one can see the new PID 876 for the sshd above.

root@mountain:~# ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.4 0.0 1312 100 ? S 18:37 0:04 init [3]
root 2 0.0 0.0 0 0 ? SWN 18:37 0:00 [ksoftirqd/0]
root 3 0.0 0.0 0 0 ? SW< 18:37 0:00 [events/0]
root 4 0.0 0.0 0 0 ? SW 18:37 0:00 [pdflush]
root 5 0.0 0.0 0 0 ? SW 18:37 0:00 [pdflush]
root 6 0.2 0.0 0 0 ? SW 18:37 0:02 [kswapd0]
root 7 0.0 0.0 0 0 ? SW< 18:37 0:00 [aio/0]
root 326 0.0 0.0 0 0 ? SW 18:37 0:00 [eth0]
root 396 0.0 0.0 1368 92 ? S 18:37 0:00 syslogd -m 0
root 401 0.0 0.0 1300 52 ? S 18:37 0:00 klogd -x
rpc 421 0.0 0.0 1444 44 ? S 18:37 0:00 portmap
root 534 0.0 0.0 2568 224 ? S 18:37 0:00 /usr/sbin/sshd
root 544 0.0 0.0 1284 48 tty1 S 18:37 0:00 /sbin/mingetty tty1
root 545 0.0 0.0 1300 48 ttyS1 S 18:37 0:00 /sbin/agetty -h ttyS1 38400 linux
root 548 0.0 0.0 3352 256 ? S 18:38 0:00 /usr/sbin/sshd
rwhron 549 0.0 0.0 2404 36 pts/0 S 18:38 0:00 -bash
root 593 0.0 0.0 2268 52 pts/0 S 18:38 0:00 su -
root 594 0.0 0.0 2400 36 pts/0 S 18:38 0:00 -bash
root 645 0.0 0.0 3352 304 ? R 18:38 0:00 /usr/sbin/sshd
rwhron 646 0.0 0.0 2404 36 pts/1 S 18:38 0:00 -bash
root 690 0.0 0.0 2268 52 pts/1 S 18:38 0:00 su -
root 691 0.0 0.1 2400 520 pts/1 S 18:38 0:00 -bash
root 741 0.0 0.0 3352 304 ? S 18:38 0:00 /usr/sbin/sshd
rwhron 742 0.0 0.0 2404 36 pts/2 S 18:38 0:00 -bash
root 786 0.0 0.0 2268 52 pts/2 S 18:38 0:00 su -
root 787 0.0 0.1 2400 520 pts/2 S< 18:38 0:00 -bash
root 844 18.6 0.0 1460 224 pts/0 R 18:41 2:10 ./irman
root 845 0.0 0.0 0 0 pts/0 Z 18:41 0:00 [irman <defunct>]
root 846 1.7 0.0 0 0 pts/0 Z 18:41 0:12 [irman <defunct>]
root 848 4.8 0.0 0 0 pts/0 Z 18:41 0:32 [mem_load <defunct>]
root 849 1.8 0.0 0 0 pts/0 Z 18:41 0:12 [irman <defunct>]
root 850 0.0 0.0 0 0 pts/0 Z 18:43 0:00 [io_load <defunct>]
root 851 1.3 0.0 0 0 pts/0 Z 18:43 0:07 [irman <defunct>]
root 855 9.0 0.0 1300 324 pts/0 S 18:44 0:45 process_load --processes 10 --recordsize 10000 --injections 2
root 857 7.5 0.0 1288 276 pts/0 S 18:44 0:37 child_process 10000 0 10
root 858 7.9 0.0 1288 276 pts/0 S 18:44 0:39 child_process 10000 3 12
root 859 13.1 0.0 1288 276 pts/0 S 18:44 1:05 child_process 10000 11 14
root 860 13.5 0.0 1288 276 pts/0 R 18:44 1:07 child_process 10000 13 16
root 861 8.0 0.0 1288 276 pts/0 R 18:44 0:40 child_process 10000 15 18
root 862 10.6 0.0 1288 276 pts/0 S 18:44 0:53 child_process 10000 17 20
root 863 11.3 0.0 1288 276 pts/0 S 18:44 0:56 child_process 10000 19 22
root 864 8.8 0.0 1288 276 pts/0 S 18:44 0:43 child_process 10000 21 24
root 865 7.9 0.0 1288 276 pts/0 S 18:44 0:39 child_process 10000 23 26
root 868 0.0 0.0 2568 108 ? R 18:47 0:00 /usr/sbin/sshd
root 876 0.0 0.0 2568 252 ? R 18:52 0:00 /usr/sbin/sshd
root 877 0.0 0.1 2544 668 pts/1 R 18:53 0:00 ps aux


This is some info on PID 876 (sshd child):

root@mountain:/proc/876# cat cmdline
/usr/sbin/sshd
root@mountain:/proc/876# cat status
Name: sshd
State: R (running)
Tgid: 876
Pid: 876
PPid: 534
TracerPid: 0
Uid: 0 0 0 0
Gid: 0 0 0 0
FDSize: 32
Groups:
VmSize: 2568 kB
VmLck: 0 kB
VmRSS: 252 kB
VmData: 100 kB
VmStk: 12 kB
VmExe: 248 kB
VmLib: 2108 kB
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 8000000000001000
SigCgt: 0000000000000000
CapInh: 0000000000000000
CapPrm: 00000000fffffeff
CapEff: 00000000fffffeff
root@mountain:/proc/876# cat wchan
0
--
Randy Hron
http://home.earthlink.net/~rwhron/kernel/bigbox.html

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