Hi Tom,
On 07/24/2013 09:45 AM, [email protected] wrote:
When running an IOC with just devIocStats in it, all of the scan
tasks seem to pause for up to 300 seconds (about half of the pauses
are between 299 and 301 seconds), then resume. During this time an
existing ssh connection to the server will continue to work, but
channel access monitors may time out. R3.14.8.2, R3.14.11 and
R3.14.12.3 IOCs are all affected. dmesg and /var/log/messages show
nothing suspicious, and cat /proc/sys/kernel/random/entropy_avail
returns 3968.
Interesting problem...
Does this have anything to do with devIocStats and the fact that you're
presumably running the IOC as a real-time process? I don't know the
internals of that module running on Linux, but the old VxStats module on
vxWorks has a lowest-priority idle thread that every so often busy-waits
for a specific period of time to measure how much work the CPU does in
the higher priority threads. I could see a problem if devIocStats is
trying to use the same technique on Linux because IIRC all real-time
(SCHED_FIFO) threads still have a higher priority than regular threads,
and this could cause the effect you're seeing. Why it only seems to
affect diskless systems is still a bit of a question, but I could think
up some reasons for that.
Take a look at the internals of devIocStats, and if it has such an idle
task try disabling it (it should be asking the OS instead of trying to
measure it anyway). Alternatively, see if not running the IOC as a
real-time process stops the problem.
HTH,
- Andrew
--
Advertising may be described as the science of arresting the human
intelligence long enough to get money from it. -- Stephen Leacock
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