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Miscellaneous Parameters

rmem_max
echo 268435456 > /proc/sys/net/core/rmem_max
vm.max_map_count

For the pgp driver this parameter needs to be increased in /etc/sysctl.conf


# grep vm /etc/sysctl.conf 
vm.max_map_count=1000000
#


DAQ Setup of DSS/FFB Nodes (LCLS-I)

Link here

CPU Frequency Governor

All daq nodes should run the cpu frequency governor in "performance mode."

As of this writing (May 2, 2022) the daq node daq-xpp-cam02 is not running the cpu frequency governor in "performance" mode.
It appears to be running in "ondemand" mode, which  "tries to use the slowest speed as much as possible, but quickly switches up or down when needed."

example of WRONG scaling_governor setting
$ hostname
daq-xpp-cam02
$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
ondemand
$

The "ondemand" setting is intended to reduce battery usage for portable devices.

Hyperthreading

The case for enabling hyperthreading

In Progress

The case for disabling hyperthreading
March 2015 email 
From: Ford, Christopher <caf@slac.stanford.edu>
Sent: Thursday, March 26, 2015 4:45 PM
To: pcds-daq-l
Subject: SXR: hyperthreading enabled on daq-sxr-cam02 and '03?

Folks,

While testing the Andor camera  I learned that some DAQ nodes were known to work better than others for this USB-based device.
Tomy writes, "One example I remember is that daq-sxr-cam01 was okay to run for hours, but daq-sxr-cam{02,03} would hang after some minutes."
Today I took a closer look, and I noticed that hyperthreading seems to be enabled on daq-sxr-cam02 and '03, where Andor fails.
Hyperthreading seems to be *disabled* on daq-sxr-cam01, where Andor runs well.

Even if hyperthreading is not proven to cause Andor failures on daq-sxr-cam02 and '03, it should not be enabled there.
Hyperthreading is not a feature useful for real-time systems, and it's not worth our time debugging this extra unknown.

Thanks,
 -caf

[caf@psdev02 03]$ ssh daq-sxr-cam01 cat /sys/devices/system/cpu/cpu0/topology/thread_siblings_list
0
[caf@psdev02 03]$ ssh daq-sxr-cam02 cat /sys/devices/system/cpu/cpu0/topology/thread_siblings_list
0,8
[caf@psdev02 03]$ ssh daq-sxr-cam03 cat /sys/devices/system/cpu/cpu0/topology/thread_siblings_list
0,8
[caf@psdev02 03]$
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