> > P.S. Observe the ever present unexplained event rate fluctuations between 130-140 event/sec.
> 
> An important aspect of optimizing your system is to keep the network traffic under control. I use GBit Ethernet between FE and BE, and make sure the switch 
> can accomodate all accumulated network traffic through its backplane. This way I do not have any TCP retransmits which kill you. Like if a single low-level 
> ethernet packet is lost due to collision, the TCP stack retransmits it. Depending on the local settings, this can be after a timeout of one (!) second, which 
> punches already a hole in your data rate. On the MSCB system actually I use UDP packets, where I schedule the retransmit myself. For a LAN, 10-100ms timeout 
> is there enough. The one second is optimized for a WAN (like between two continents) where this is fine, but it is not what you want on a LAN system. Also 
> make sure that the outgoing traffic (lazylogger) uses a different network card than the incoming traffic. I found that this also helps a lot.
> 

In typical applications at TRIUMF we do not setup a private network for the data traffic - data from VME to backend computer
and data from backend computer to DCACHE all go through the TRIUMF network.

This is justified by the required data rates - the highest data rate experiment running right now is PIENU - running
at about 10 M/s sustained, nominally April through December. (This is 20% of the data rate of the present benchmark).

The next highest data rate experiment is T2K/ND280 in Japan running at about 20 M/s (neutrino beam, data rate
is dominated by calibration events).

All other experiments at TRIUMF run at lower data rates (low intensity light ion beams), but we are planning for an experiment
that will run at 300 M/s sustained over 1 week of scheduled beam time.

But we do have the technical capability to separate data traffic from the TRIUMF network - the VME processors and
the backend computers all have dual GigE NICs.

(I did not say so, but obviously the present benchmark at 50 M/s VME to backend and 20-30 M/s from backend to HDFS is a GigE network).

(I am not monitoring the TCP loss and retransmit rates at present time)

(The network switch between VME and backend is a "the cheapest available" rackmountable 8-port GigE switch. The network between
the backend and the HDFS nodes is mostly Nortel 48-port GigE edge switches with single-GigE uplinks to the core router).

K.O.

> > > I am recording here the results from a test VME system using four VF48 waveform digitizers

Now we look at the detail of the event readout, or if you want, the real-time properties of the MIDAS 
multithreaded VME frontend program.

The benchmark system includes a TRIUMF-made VME-NIMIO32 VME trigger module which records the 
time of the trigger and provides a 20 MHz timestamp register. The frontend program is instrumented to 
save the trigger time and readout timing data into a special "trigger" bank ("VTR0"). The ROOTANA-based 
MIDAS analyzer is used to analyze this data and to make these plots.

Timing data is recorded like this:

NIM trigger signal ---> latched into the IO32 trigger time register (VTR0 "trigger time")
...
int read_event(pevent, etc) {
VTR0 "trigger time" = io32->latched_trigger_time();
VTR0 "readout start time" = io32->timestamp();
read the VF48 data
io32->release_busy();
VTR0 "readout end time" = io32->timestamp();
}

From the VTR0 time data, we compute these values:

1) "trigger latency" = "readout start time" - "trigger time" --- the time it takes us to "see" the trigger
2) "readout time" = "readout end time" - "readout start time" --- the time it takes to read the VF48 data
3) "busy time" = "readout end time" - "trigger time" --- time during which the "DAQ busy" trigger veto is 
active.
also computed is
4) "time between events" = "trigger time" - "time of previous trigger"

And plot them on the attached graphs:

1) "trigger latency" - we see average trigger latency is 5 usec with hardly any events taking more than 10 
usec (notice the log Y scale!). Also notice that there are 35 events that took longer that 100 usec (0.7% out 
of 5000 events).

So how "real time" is this? For "hard real time" the trigger latency should never exceed some maximum, 
which is determined by formal analysis or experimentally (in which case it will carry an experimental error 
bar - "response time is always less than X usec with probability 99.9...%" - the better system will have 
smaller X and more nines). Since I did not record the maximum latency, I can only claim that the 
"response time is always less than 1 sec, I am pretty sure of it".

For "soft real time" systems, such as subatomic particle physics DAQ systems, one is permitted to exceed 
that maximum response time, but "not too often". Such systems are characterized by the quantities 
derived from the present plot (mean response time, frequency of exceeding some deadlines, etc). The 
quality of a soft real time system is usually judged by non-DAQ criteria (i.e. if the DAQ for the T2K/ND280 
experiment does not respond within 20 msec, a neutrino beam spill an be lost and the experiment is 
required to report the number of lost spills to the weekly facility management meeting).

Can the trigger latency be improved by using interrupts instead of polling? Remember that on most 
hardware, the VME and PCI bus access time is around 1 usec and trigger latency of 5-10 usec corresponds 
to roughly 5-10 reads of a PCI or VME register. So there is not much room for speed up. Consider that an 
interrupt handler has to perform at least 2-3 PCI register reads (to determine the source of the interrupt 
and to clear the interrupt condition), it has to wake up the right process and do a rather slow CPU context 
switch, maybe do a cross-CPU interrupt (if VME interrupts are routed to the wrong CPU core). All this 
takes time. Then the Linux kernel interrupt latency comes into play. All this is overhead absent in pure-
polling implementations. (Yes, burning a CPU core to poll for data is wasteful, but is there any other use 
for this CPU core? With a dual-core CPU, the 1st core polls for data, the 2nd core runs mfe.c, the TCP/IP 
stack and the ethernet transmitter.)

2) "readout time" - between 7 and 8 msec, corresponding to the 50 Mbytes/sec VME block transfer rate. 
No events taking more than 10 msec. (Could claim hard real time performance here).

3) "busy time" - for the simple benchmark system it is a boring sum of plots (1) and (2). The mean busy 
time ("dead time") goes straight into the formula for computing cross-sections (if that is what you do).

4) "time between events" - provides an independent measurement of dead time - one can see that no 
event takes less than 7 msec to process and 27 events took longer than 10 msec (0.65% out of 4154 
events). If the trigger were cosmic rays instead of a pulser, this plot would also measure the cosmic ray 
event rate - one would see the exponential shape of the Poisson distribution (linear on Log scale, with the 
slope being the cosmic event rate).


K.O.

> > > > I am recording here the results from a test VME system using four VF48 
waveform digitizers

Last message from this series. After all the tuning, I reduce the trigger rate 
from 120 Hz to 100 Hz to see
what happens when the backend computer is not overloaded and has some spare 
capacity.

event rate: 100 Hz (down from 120 Hz)
data rate: 37 Mbytes/sec (down from 50 M/s)
mlogger cpu use: 65% (down from 99%)

Attached:

1) trigger rate event plot: now the rate is solid 100 Hz without dropouts
2) CPU and Network plots frog ganglia: the spikes is lazylogger saving mid.gz 
files to HDFS storage
3) time structure plots:
a) trigger latency: mean 5 us, most below 10 us, 59 events (0.046%) longer than 
100 us, (bottom left graph) 7000 us is longest latency observed.
b) readout time is 7000-8000 us (same as before - VME data rate is independant 
from the trigger rate)
c) busy time: mean 7.2 us, 12 events (0.0094%) longer than 10 ms, longest busy 
time ever observed is 17 ms (bottom middle graph)
d) time between events is 10 ms (100 Hz pulser trigger), 1 event was missed 
about 10 times (spike at 20 ms) (0.0085%), more than 1 event missed never (no 
spike at 30 ms, 40 ms, etc).


CPU use on the backend computer:

top - 16:30:59 up 75 days, 35 min,  6 users,  load average: 0.98, 0.99, 1.01
Tasks: 206 total,   3 running, 203 sleeping,   0 stopped,   0 zombie
Cpu(s): 39.3%us,  8.2%sy,  0.0%ni, 39.4%id,  5.7%wa,  0.3%hi,  7.2%si,  0.0%st
Mem:   3925556k total,  3404192k used,   521364k free,     8792k buffers
Swap: 32766900k total,   296304k used, 32470596k free,  2477268k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND            
 5826 trinat    20   0  441m 292m 287m R 65.8  7.6   2215:16 mlogger            
26756 trinat    20   0  310m 288m 288m S 16.8  7.5  34:32.03 mserver            
29005 olchansk  20   0  206m  39m  17m R 14.7  1.0  26:19.42 ana_vf48.exe       
 7878 olchansk  20   0   99m 3988  740 S  7.7  0.1  27:06.34 sshd               
29012 trinat    20   0  314m 288m 288m S  2.8  7.5   4:22.14 mserver            
23317 root      20   0     0    0    0 S  1.4  0.0  24:21.52 flush-9:3     


K.O.

I started to get web browser popups about "midas wants to show notifications, 
block/allow/x". is this a glitch or a new unannounced/undocumented feature? 
google chrome on macos. K.O.

> I started to get web browser popups about "midas wants to show notifications, 
> block/allow/x". is this a glitch or a new unannounced/undocumented feature? 
> google chrome on macos. K.O.

https://bitbucket.org/tmidas/midas/commits/e101dea764c647211c560a68db7ecda1834198db

I did not consider this a significant feature to be announced here. Just a few lines 
of code. You can turn it on/off via the "Config" web page.

Stefan

> > I started to get web browser popups about "midas wants to show notifications, 
> > block/allow/x". is this a glitch or a new unannounced/undocumented feature? 
> > google chrome on macos. K.O.
> 
> https://bitbucket.org/tmidas/midas/commits/e101dea764c647211c560a68db7ecda1834198db
> 
> I did not consider this a significant feature to be announced here. Just a few lines 
> of code. You can turn it on/off via the "Config" web page.
> 
> Stefan

Now as I look at it again I realized that the config check boxes had a bug. I fixed that 
and now the disable should work correctly.

This feature was asked by some people who monitor an experiment and have the browser window 
in the background, also have sound off (large office). So desktop notifications are a good 
thing for them.

Stefan

> This feature was asked by some people ...

"show notifications" popups are strongly associated with disreputable web sites (presumably to 
push spam), it was surprising to see it from midas.

K.O.

> > This feature was asked by some people ...
> 
> "show notifications" popups are strongly associated with disreputable web sites (presumably to 
> push spam), it was surprising to see it from midas.
> 
> K.O.

I agree. But unlike emails (where you get lots of spam as well), you can nicely blacklist/whitelist 
desktop notifications. I suppress all of them except the one for MIDAS. This allows me to watch our 
experiment without staring on the web page all the time.

The main question here is maybe if the desktop notification should be on or off by default (for a 
fresh browser). While you always can change that via the mhttpd "Config" page, the default value is 
chosen by the system. I thought I put it to "on" so people can experience it, and then turn it off if 
they don't like. Having them off by default, most people never would notice this possibility. But I'm 
open to a discussion here.

Stefan

I updated the links on the midas wiki to the doxygen-generated documentation for MIDAS that you 
get after running "git clone midas; cd midas; make dox; firefox html/index.html".

Correct link is:
https://daq.triumf.ca/~daqweb/doc/midas-devel/html/

This takes you to a daily/nightly generated snapshot of the midas develop branch and the 
generated documentation with full call graphs.

Previous links were deficient is different ways:
- referred to http://ladd00 instead of https://daq
- referred to wrong path ~daqweb/doc/midas instead of ~daqweb/doc/midas-devel
- referred to the obsolete doxygen generator in midas/doc/html instead of midas/html.

If wrong links are still present on the midas wiki, please let us know and we will fix them.
K.O.

The midas wiki at https://midas.triumf.ca was updated to mediawiki 1.22.4 - the latest production version. 
If you see any problems, please report them to this elog. K.O.

midas wiki at https://midas.triumf.ca/MidasWiki/index.php/Main_Page
was updated to MediaWiki version 1.27.1, the current MediaWiki LTS release.
Everything should work as before, but if you see any problems or anomalies, please report
them on this forum here.
K.O.

the midas wiki was updated to the latest LTS point release 1.27.5.

Also, an installation error was fixed that prevented confirmation of new accounts (git checkout 
REL1_28 instead of REL1_27, resulting in a version mismatch).

Support for MediaWiki LTS release 1.27 ends this Summer.

Next LTS release series is 1.31, see https://en.wikipedia.org/wiki/MediaWiki_version_history

This version requires php version 7 or newer which comes standard with ubuntu LTS 18.04 
and el8 (RHEL8), but not with el6 (SL6) and el7 (CentOS-7).

I guess we shall start planning this upgrade and the move of the wiki to a new host machine.

K.O.

the midas wiki was updated to the latest LTS point release 1.27.7, the latest (last?) security update.

mediawiki series 1.27 is now officially EOL, see
https://lists.wikimedia.org/pipermail/mediawiki-announce/2019-June/000231.html

they recommend that all users upgrade to the current LTS series 1.31.

for us it means moving the wiki from the present el6 (SL6) computer to
a more up-to-date platform (el8 or ubuntu LTS 18.04).

K.O.

The midas wiki at https://midas.triumf.ca has been upgraded to mediawiki version 1.25.2 (current 
production version). If you see any problems, please report them on this forum. K.O.

the midas release 2019-03 is ready for general use.

main changes from previous releases (midas-2017-10, midas-2018-12 and midas-2019-02):

- change to the midas URL scheme
- removal of cm_watchdog()
- rewrite of event buffer code (and fix of hard to trigger event buffer corruption bug)
- fully thread safe odb and event buffer code (except for rpc_send_event())
- corrected compatibility problems wrt older versions of midas when serving custom web pages via odb /custom/path

To obtain this release, either checkout the top of branch feature/midas-2019-03 (recommended)
or checkout the tag midas-2019-03-f.

K.O.

> the midas release 2019-03 is ready for general use.

first ever bug fix release on a git release branch.

fixed a crash if frontend built against this midas is connected to mserver from old (pre-db_watch) midas (size mismatch of MSG_ODB 
message).

to use this update:

# recommended:
git pull
git checkout feature/midas-2019-03
git pull
make ...

# or checkout "detached HEAD"
git pull
git checkout midas-2019-03-g
make ...

odbedit "ver" should report:

GIT revision:       Wed May 22 07:35:11 2019 -0700 - midas-2019-03-g on branch feature/midas-2019-03

K.O.

P.S. Thanks for finding this bug go to Greg Hackman on TIGRESS and EMMA experiments at TRIUMF.

K.O.

> > the midas release 2019-03 is ready for general use.

A bug fix update for midas-2019-03:

- fix broken expand_env() in mhttpd
- fix "Invalid name passed to db_create_key: should not be an empty string" in midas.log when loading the MIDAS status page if one of the alarms has empty 
class name.

odbedit "ver" should report: Thu Jun 6 18:02:14 2019 -0700 - midas-2019-03-h on branch feature/midas-2019-03

K.O.

We are happy to the midas release "midas-2019-06" with the build system implemented in cmake and the midas, mxml and mscb 
projects switched to C++.

Changes since midas-2019-03:

minor bug fixes
switch of midas build to c++ with c++ linkage (no "extern C")
switch of midas build to cmake
removal of $(OS_DIR) from the midas library and bin paths (use $MIDASSYS/lib instead of $MIDASSYS/linux/lib)
mxml and mscb are implemented as git submodules

Please review the following guide to update midas from previous release midas-2019-03 or older.

Update the code:

git checkout develop
git pull
git checkout feature/midas-2019-06
git pull
git submodule update --init # this will checkout correct versions of mxml and mscb
make clean
make cclean
rm -rf linux/bin
rm -rf linux/lib
rmdir linux
make cmake3 # or "make cmake" on ubuntu and macos
ls -l bin/odbedit bin/mlogger

Update experiment environment:

- change PATH from $MIDASSYS/linux/bin to $MIDASSYS/bin

Cleanup unneeded stuff:

- remove $HOME/packages/mxml (new location $MIDASSYS/mxml)
- remove $HOME/packages/mscb (new location $MIDASSYS/mscb)

Update experiment frontend build:

- change Makefile to remove $(OS_DIR) from library search path ($MIDASSYS/linux/lib becomes $MIDASSYS/lib)
- change Makefile to set mxml include path from $MIDASSYS/../mxml to $MIDASSYS/mxml (to avoid including the wrong 
version of mxml/strlcpy.h)
- update frontend code to use mfe.h and build as C++, see https://midas.triumf.ca/elog/Midas/1526

K.O.

Please note that 

"make cmake" / "make cmake3"

is an abbreviation for the "normal" cmake command chain. Users familiar with cmake can also do the standard command chain:

mkdir build
cd build
cmake ..
make
make install


- Stefan

> We are happy to the midas release "midas-2019-06" with the build system implemented in cmake and the midas, mxml and mscb 
> projects switched to C++.
> 
> Changes since midas-2019-03:
> 
> minor bug fixes
> switch of midas build to c++ with c++ linkage (no "extern C")
> switch of midas build to cmake
> removal of $(OS_DIR) from the midas library and bin paths (use $MIDASSYS/lib instead of $MIDASSYS/linux/lib)
> mxml and mscb are implemented as git submodules
> 
> Please review the following guide to update midas from previous release midas-2019-03 or older.
> 
> Update the code:
> 
> git checkout develop
> git pull
> git checkout feature/midas-2019-06
> git pull
> git submodule update --init # this will checkout correct versions of mxml and mscb
> make clean
> make cclean
> rm -rf linux/bin
> rm -rf linux/lib
> rmdir linux
> make cmake3 # or "make cmake" on ubuntu and macos
> ls -l bin/odbedit bin/mlogger
> 
> Update experiment environment:
> 
> - change PATH from $MIDASSYS/linux/bin to $MIDASSYS/bin
> 
> Cleanup unneeded stuff:
> 
> - remove $HOME/packages/mxml (new location $MIDASSYS/mxml)
> - remove $HOME/packages/mscb (new location $MIDASSYS/mscb)
> 
> Update experiment frontend build:
> 
> - change Makefile to remove $(OS_DIR) from library search path ($MIDASSYS/linux/lib becomes $MIDASSYS/lib)
> - change Makefile to set mxml include path from $MIDASSYS/../mxml to $MIDASSYS/mxml (to avoid including the wrong 
> version of mxml/strlcpy.h)
> - update frontend code to use mfe.h and build as C++, see https://midas.triumf.ca/elog/Midas/1526
> 
> K.O.

I created the release branch for midas-2019-09 and tag midas-2019-09-a.

Since the previous release midas-2019-06, some news:

- new history graphics (Stefan)
- c++ frontend framework mvodb.h and tmfe.h merged from ALPHA-g (K.O.)
- we think we have all the fallout from switching to cmake and to c++11 sorted out

There is a number of known problems with the current code, see the bitbucket bug tracker:
https://bitbucket.org/tmidas/midas/issues?status=new&status=open

Hopefully we can use this release as a baseline for more testing and with luck we will
fix all the pending bugs and add all the pending missing code (the new sequencer web pages,
the "m" analyzer, etc) quickly and our next release midas-2019-10 will be the best midas ever.

To obtain this release, either checkout the top of branch feature/midas-2019-09 (recommended)
or checkout the tag midas-2019-09-a.

If you are using the last pre-cmake/c++ release midas-2019-03, I recommend that you stay with it
until our next release midas-2019-10.

K.O.