Have you read what I wrote? The current ctrl-c handler just sets the _ctrlc_pressed flag. It might be that some programs do not correctly interprete the return of cm_yield(), certainly the frontend does it correctly. On the SECOND ctrl-c, the program gets 
(internally) hard aborted, equivalent to calling abort(). Not sure if the code works everywhere, I see now that cm_yield(() should maybe return SS_ABORT like 

if (_ctrlc_pressed)
  return SS_ABORT;

then command_loop will exit gracefully. Have to check mfe.c, mlogger.c etc. if they all check for SS_ABORT returned from cm_yield().

> > Not sure if you realized, but there is a two-stage Ctrl-C handling inside midas.
> 
> Hmm... I am looking at the ctrl-c handler inside odbedit.
> 
> Yes, and the original bug report is against odbedit - press of ctrl-c in odbedit corrupts odb,
> see stack trace in https://bitbucket.org/tmidas/midas/issues/99
> 
> So maybe only the odbedit ctrl-c handler is defective...
> 
> I will take a look at what the other ctrl-c handler does.
> 
> Safest is probably to call exit() without calling cm_disconnect_experiment().
> 
> From the ctrl-c handler, if we call cm_disconnect_experiment() -
> - if we hold odb locked, we deadlock (after I remove the recursive mutex) or corrupt odb (if we run form inside db_create or db_set_data).
> - if we run from inside db_lock/unlock, we abort() (with my newly added protection) or explode (if we run from inside mprotect(), like in the stack strace in the bug report)
> 
> I would say, from a signal handler, only safe things are - set a flag, or abort()/exit().
> 
> exit() is not super safe because the user may have attached some code to it that may access odb. (our
> default atexit() handler just prints an error message).
> 
> K.O.
> 
> 
> > The first time you hit ctrl-c, the handler just sets a flag for the main event loop, so that the program can gracefully exit without trouble. This is 
> > done inside cm_ctrlc_handler(), which sets _ctrlc_pressed true if called. Then cm_yield() tests this flag and returns RPC_SHUTDOWN if so. I agree not very obvious, maybe we should return a more appropriate status. So the 
> > main loop must check the return status of cm_yield() and break if it's RPC_SHUTDOWN. The frontend framework mfe.c does this for example in
> > 
> >  while (status != RPC_SHUTDOWN && status != SS_ABORT);
> > 
> > Any use-written program should do the same (well, probably this is nowhere documented).
> > 
> > Now when the program does not exit (e.g. if it's in an infinite loop), then the second ctrl-c creates a hard abort and terminates the program non-gracefully, which as you noticed can lead to undesired results. All the 
> > semaphores (at least when I implemented it) had a SEM_UNDO flag when obtaining ownership. This means that if the semaphore is locked and the process who owns it terminates (even with a hard kill), then the semaphore 
> > is released by the OS. This way a crashed program cannot keep the ODB locked for example. Not sure that with all your modifications in the semaphore calls this functionality is still guaranteed.
> > 
> > Stefan
> > 
> > > Even with the cm_watchdog signal removed, some trouble from UNIX signals remains.
> > > 
> > > This time, when one presses Ctrl-C at the wrong time, the Ctrl-C signal handler will run at the wrong time
> > > and strange things will happen (including odb corruption).
> > > 
> > > In the captured stack trace, I pressed Ctrl-C right when odbedit was inside db_lock_database(). I had to make special
> > > arrangements to make it happen, but I have seen it happen in normal use when running experiments.
> > > 
> > > K.O.
> > > 
> > > (lldb) bt
> > > * thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
> > >   * frame #0: 0x00007fff6c2ceb66 libsystem_kernel.dylib`__pthread_kill + 10
> > >     frame #1: 0x00007fff6c499080 libsystem_pthread.dylib`pthread_kill + 333
> > >     frame #2: 0x00007fff6c22a1ae libsystem_c.dylib`abort + 127
> > >     frame #3: 0x00000001057ccf95 odbedit`db_lock_database(hDB=<unavailable>) at odb.c:2048 [opt]
> > >     frame #4: 0x00000001057aed9d odbedit`cm_delete_client_info(hDB=1, pid=46856) at midas.c:1702 [opt]
> > >     frame #5: 0x00000001057b08fe odbedit`cm_disconnect_experiment at midas.c:2704 [opt]
> > >     frame #6: 0x00000001057a8231 odbedit`ctrlc_odbedit(i=<unavailable>) at odbedit.cxx:2863 [opt]
> > >     frame #7: 0x00007fff6c48cf5a libsystem_platform.dylib`_sigtramp + 26
> > >     frame #8: 0x00007fff6c2ced83 libsystem_kernel.dylib`__semwait_signal + 11
> > >     frame #9: 0x00007fff6c249724 libsystem_c.dylib`nanosleep + 199
> > >     frame #10: 0x00007fff6c249586 libsystem_c.dylib`sleep + 41
> > >     frame #11: 0x00000001057cce6b odbedit`db_lock_database(hDB=<unavailable>) at odb.c:2057 [opt]
> > >     frame #12: 0x00000001057e129a odbedit`db_get_record_size(hDB=1, hKey=141848, align=8, buf_size=0x00007ffeea44c14c) at odb.c:10232 [opt]
> > >     frame #13: 0x00000001057e1b58 odbedit`db_get_record1(hDB=1, hKey=141848, data=0x00007ffeea44c320, buf_size=0x00007ffeea44c2a8, align=0, rec_str="[.]\nWrite system message = BOOL : 
> > > y\nWrite Elog message = BOOL : n\nSystem message interval = INT : 60\nSystem message last = DWORD : 0\nExecute command = STRING : [256] \nExecute interval = INT : 0\nExecute last = DWORD : 
> > > 0\nStop run = BOOL : n\nDisplay BGColor = STRING : [32] red\nDisplay FGColor = STRING : [32] black\n\n") at odb.c:10390 [opt]
> > >     frame #14: 0x00000001057f1de3 odbedit`al_trigger_class(alarm_class="Warning", alarm_message="This is an example alarm", first=YES) at alarm.c:389 [opt]
> > >     frame #15: 0x00000001057f19e8 odbedit`al_trigger_alarm(alarm_name="Example alarm", alarm_message="This is an example alarm", default_class="Warning", cond_str="", type=<unavailable>) at 
> > > alarm.c:310 [opt]
> > >     frame #16: 0x00000001057f2c4e odbedit`al_check at alarm.c:655 [opt]
> > >     frame #17: 0x00000001057b9f88 odbedit`cm_periodic_tasks at midas.c:5066 [opt]
> > >     frame #18: 0x00000001057ba26d odbedit`cm_yield(millisec=100) at midas.c:5137 [opt]
> > >     frame #19: 0x00000001057a30b8 odbedit`cmd_idle() at odbedit.cxx:1238 [opt]
> > >     frame #20: 0x00000001057a92df odbedit`cmd_edit(prompt="[local:javascript1:S]/>", cmd=<unavailable>, dir=(odbedit`cmd_dir(char*, int*) at odbedit.cxx:705), idle=(odbedit`cmd_idle() at 
> > > odbedit.cxx:1233))(char*, int*), int (*)()) at cmdedit.cxx:235 [opt]
> > >     frame #21: 0x00000001057a3863 odbedit`command_loop(host_name="", exp_name="javascript1", cmd="", start_dir=<unavailable>) at odbedit.cxx:1435 [opt]
> > >     frame #22: 0x00000001057a8664 odbedit`main(argc=1, argv=<unavailable>) at odbedit.cxx:2997 [opt]
> > >     frame #23: 0x00007fff6c17e015 libdyld.dylib`start + 1

> mhttpd and mlogger have been updated with potentially troublesome changes.
> These new features are now available:
> - a "feature complete" implementation of "history in an SQL database".

The mlogger SQL history driver has been updated with improvements that make this new system usable in 
production environment: the silly "create all tables on startup, every time, even if they already exist" is fixed,
mlogger survives restarts of mysqld and checks that existing sql columns have data types compatible with the 
data we are trying to write.

There are still a few trouble spots remaining. For example, in mapping midas names into sql names (sql names 
have more restrictions on permitted characters) and in reverse mapping of sql data types to midas data types. 
To properly solve this, I may have to save the midas names and data types into an additional index table.

Included is the mh2sql utility for importing existing history files into an SQL database (in the same way as if 
they were written into the database by mlogger).

The mhttpd side of this system still needs polishing, but should be already fully functional.

A preliminary version of documentation for this new SQL history system is here. After additional review and 
editing it will be committed to the midas midox documentation. Included are full instructions on enabling 
writing of midas history into a MySQL database.
http://ladd00.triumf.ca/~olchansk/midas/Internal.html#History_sql_internal

svn revision 4452
K.O.

When using "/bin/bash" shell, if I exit odbedit (and other midas programs) using ctrl-C, the terminal 
enters a funny state, "echo" is turned off (I cannot see what I type), "delete" key does not work (echoes 
^H instead).

This problem does not happen if I exit using the "exit" command or if I use the "/bin/tcsh" shell.

When this happens, the terminal can be restored to close to normal state using "stty sane", and "stty 
erase ^H".

The terminal is set into this funny state by system.c::getchar() and normal settings are never restored 
unless the midas program calls getchar(1) at the end. If the program does not finish normally, original 
terminal settings are never restored and the terminal is left in a funny state.

It is not clear why the problem does not happen with /bin/tcsh - perhaps they restore sane terminal 
settings automatically for us.
K.O.

> When using "/bin/bash" shell, if I exit odbedit (and other midas programs) using ctrl-C, the terminal 
> enters a funny state, "echo" is turned off (I cannot see what I type), "delete" key does not work (echoes 
> ^H instead).
> 
> This problem does not happen if I exit using the "exit" command or if I use the "/bin/tcsh" shell.
> 
> When this happens, the terminal can be restored to close to normal state using "stty sane", and "stty 
> erase ^H".
> 
> The terminal is set into this funny state by system.c::getchar() and normal settings are never restored 
> unless the midas program calls getchar(1) at the end. If the program does not finish normally, original 
> terminal settings are never restored and the terminal is left in a funny state.
> 
> It is not clear why the problem does not happen with /bin/tcsh - perhaps they restore sane terminal 
> settings automatically for us.
> K.O.

Who uses bash ??? And who keeps baning on Ctrl-C, when there is a nice "exit" command ;-)

Well, I implemented a simple CTRL-C handler in odbedit (Rev. 4503) which resets the terminal before exiting. 
Give it a try. Of course this cannot catch a hard kill (-9), but CTRL-C works now correctly under bash at 
least.

odbedit uses a fixed size buffer for ODB data. If an array in ODB is bugger than this size, 
db_get_data() correctly returns DB_TRUNCATED and there is no memory overwrite, but the following 
code for printing the data does not know about this truncation and proceeds printing memory 
values contained after the end of the fixed size data buffer - in the current case, this memory 
somehow had the contents of the shell history - this very confused the MIDAS users as they though 
that the funny printout was actually in ODB. This is in the print_key() function. If db_get_data() 
returns DB_TRUNCATED, it should allocate a buffer of bigger size. This (and the previous) bug found 
by the TIGRESS experiment. K.O.

We were debugging a strange problem in the event builder, where out of 14
fragments, two fragments were always getting serial number mismatches and the
serial numbers were not sequentially increasing (the other 12 fragments were
just fine).

Then we noticed in the event builder debug output that these 2 fragments were
getting assigned the same buffer handle number, despite having different names -
BUF09 and BUFTPC.

Then we looked at "ipcs", counted the buffers, and there are only 13 buffers for
14 frontends.

Aha, we went, maybe we have unlucky buffer names, renamed BUFTPC to BUFAAA and
everything started to work just fine.

It turns out that the MIDAS ss_shm_open() function uses "ftok" to convert buffer
names to SystemV shared memory keys. This "ftok" function promises to create
unique keys, but I guess, just not today.

Using a short test program, I confirmed that indeed we have unlucky buffer names
and ftok() returns duplicate keys, see below.

Apparently ftok() uses the low 16 bits of the file inode number, but in our
case, the files are NFS mounted and inode numbers are faked inside NFS. When I
run my test program on a different computer, I get non-duplicate keys. So I
guess we are double unlucky.

Test program:

#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>

int main(int argc, char* argv[])
{
  //key_t ftok(const char *pathname, int proj_id);
  
  int k1 = ftok("/home/t2kdaq/midas/nd280/backend/.BUF09.SHM", 'M');
  int k2 = ftok("/home/t2kdaq/midas/nd280/backend/.BUFTPC.SHM", 'M');
  int k3 = ftok("/home/t2kdaq/midas/nd280/backend/.BUFFGD.SHM", 'M');

  printf("key1: 0x%08x, key2: 0x%08x, key3: 0x%08x\n", k1, k2, k3);
  return 0;
}

[t2kfgd@t2knd280logger ~/xxx]$ g++ -o ftok -Wall ftok.cxx
[t2kfgd@t2knd280logger ~/xxx]$ ./ftok
key1: 0x4d138154, key2: 0x4d138154, key3: 0x4d138152

Also:

[t2kfgd@t2knd280logger ~/xxx]$ ls -li ...
14385492 -rw-r--r-- 1 t2kdaq t2kdaq  8405052 Nov 24 17:42
/home/t2kdaq/midas/nd280/backend/.BUF09.SHM
36077906 -rw-r--r-- 1 t2kdaq t2kdaq 67125308 Nov 26 10:19
/home/t2kdaq/midas/nd280/backend/.BUFFGD.SHM
36077908 -rw-r--r-- 1 t2kdaq t2kdaq  8405052 Nov 25 15:53
/home/t2kdaq/midas/nd280/backend/.BUFTPC.SHM

(hint: print the inode numbers in hex and compare to shm keys printed by the
program)

K.O.

we had a bit of trouble with open network ports recently and I now think security of MIDAS RPC 
ports needs to be tightened.

TL;DR, this is a non-trivial network configuration problem, TL required, DR up to you.

as background, right now we have two settings in ODB, "/expt/security/enable non-localhost 
RPC" set to "no" (the default) and set to "yes". Set to "no" is very secure, all RPC sockets 
listen only on the "localhost" interface (127.0.0.1) and do not accept connections from other 
computers. Set to "yes", RPC sockets accept connections from everywhere in the world, but 
immediately close them without reading any data unless connection origins are listed in ODB 
"/expt/security/RPC hosts" (white-listed).

the problem, one. for security and robustness we place most equipments on a private network 
(192.168.1.x). MIDAS frontends running on these equipments must connect to MIDAS running on 
the main computer. This requires setting "enable non-localhost RPC" to "yes" and white-listing 
all private network equipments. so far so good.

the problem, one, continued. in this configuration, the MIDAS main computer is usually also 
the network gateway (with NAT, IP forwarding, DHCP, DNS, etc). so now MIDAS RPC ports are open 
to all external connections (in the absence of restrictive firewall rules). one would hope for 
security-through-obscurity and expect that "external threat actors" will try to bother them, 
but in reality we eventually see large numbers of rejected unwanted connections logged in 
midas.log (we log the first 10 rejected connections to help with maintaining the RPC 
connections white-list).

the problem, two. central IT do not like open network ports. they run their scanners, discover 
the MIDAS RPC ports, complain about them, require lengthy explanations, etc.

it would be much better if in the typical configuration, MIDAS RPC ports did not listen on 
external interfaces (campus network). only listen on localhost and on private network 
interfaces (192.168.1.x).

I am not yet of the simplest way to implement this. But I think this is the direction we 
should go.

P.S. what about firewall rules? two problems: one: from statistic-of-one, I make mistakes 
writing firewall rules, others also will make mistakes, a literally fool-proof protection of 
MIDAS RPC ports is needed. two: RHEL-derived Linuxes by-default have restrictive firewall 
rules, and this is good for security, except that there is a failure mode where at boot time 
something can go wrong and firewall rules are not loaded at all. we have seen this happen. 
this is a complete disaster on a system that depends on firewall rules for security. better to 
have secure applications (TCP ports protected by design and by app internals) with firewall 
rules providing a secondary layer of protection.

P.P.S. what about MIDAS frontend initial connection to the mserver? this is currently very 
insecure, but the vulnerability window is very small. Ideally we should rework the mserver 
connection to make it simpler, more secure and compatible with SSH tunneling.

P.P.S. Typical network diagram:

internet - campus firewall - campus network - MIDAS host (MIDAS) - 192.168.1.x network - power 
supplies, digitizers, MIDAS frontends.

P.P.S. mserver connection sequence:

1) midas frontend opens 3 tcp sockets, connections permitted from anywhere
2) midas frontend opens tcp socket to main mserver, sends port numbers of the 3 tcp sockets
3) main mserver forks out a secondary (per-client) mserver
4) secondary mserver connects to the 3 tcp sockets of the midas frontend created in (1)
5) from here midas rpc works
6) midas frontend loads the RPC white-list
7) from here MIDAS RPC sockets are secure (protected by the white-list).

(the 3 sockets are: RPC recv_sock, RPC send_sock and event_sock)

P.P.S. MIDAS UDP sockets used for event buffer and odb notifications are secure, they bind to 
localhost interface and do not accept external connections.

K.O.

> I recently upgraded my macbook to MacOS 10.11. 
> [ and midas would not compile ]
> It seems that MacOS has now fully removed openssl ...

My read of tea leaves - the macos version of openssl was so old it was almost useless, did not support any of the modern HTTPS 
features. So to use mhttpd with https you pretty much had to install openssl from macports anyway. For macos 10.11 maybe they 
looked at upgrading to newer version, but since the openssl kerfuffle last year, there is several forks of openssl (the OpenBSD fork 
named libressl is the best, IMO), so rather than picking and choosing, they deleted the whole thing.

Now back to MIDAS.

We use the mongoose web server module and I have expected by now for them to make a move on improving HTTPS support, but no 
move happened.

Right now mongoose support OpenSSL only (I would expect the OpenBSD LibreSSL fork to work to of the box, too). Other then that, 
they have:
a) their own mickey-mouse https library (krypton) which does not support any modern cryptography (RC4 only - when RC4 is known to 
be useless).
b) an adapter library (polar) for interfacing with PolarSSL (mbedtls)

At this point I would rather abandon the implicit dependency on the system-provided openssl and have an explicit dependancy on a 
modern https crypto library.

Option (b) would work for us - 
1) add "git clone mbedtls; cd mbedtls; make" to midas build instructions
2) add polarssl_compat.c to midas git (from cessanta/polar repo)
3) retest mhttpd against ssllabs https scanner, retest against all web browsers.

The downside of this route is loss of automatic nightly updates to the https crypto library (for better or for worse).

K.O.

P.S. Because on MacOS use of openssl from macports is pretty much required, it should be moved from the "tricks" page to the 
standard midas installation instructions ("install required packages").

Here is the list of known problems I am aware of and of fixes not yet committed
to midas svn:

Here is the list of known problems I am aware of and of fixes not yet committed
to midas svn:

1) added variable /equiment/foo/common/PerVariableHistory breaks stuff (mostly
mhttpd). It is not clear how this problem escaped my pre-commit checks. This
per-equipment variable enables the per-variable history for the given equipment.
Local consensus is that this variable should not be in "common" and should not
be in "settings". Probably in "/history"? Or have only one variable to enable
this for all equipments at once (like we do in ALPHA).

2) writing compressed midas files (foo.mid.gz) crashes the mlogger when file
size reaches 2 GBytes. This problem could be new in SL5.1.

3) when a midas client becomes unresponsive, runs cannot be stopped using the
"stop" button in mhttpd. This is because cm_transition() loops over all attached
clients, but never removes clients that are known to be dead. Proposed fix is to
call cm_check_client() for each client before calling their rpc transition handler.

4) the discussed before fix for reading broken history files (skip bad data).

5) mhttpd history "export" button needs to be fixed (by request from ALPHA). At
present it either does not return all exiting data or crashes mhttpd. (no fix)

6) mhttpd ODB editor in "set value" page, the "cancel" button is broken (needs
to be corrected for "relative URL"). (no fix)

7) mhttpd needs AJAX-style methods for reading and writing ODB. (no fix)

K.O.

> Here is the list of known problems I am aware of and of fixes not yet committed
> to midas svn:
> 
> 1) added variable /equiment/foo/common/PerVariableHistory

corrected in svn revision 4203, read
http://savannah.psi.ch/viewcvs/trunk/src/mlogger.c?root=midas&rev=4203&sortby=rev&view=log

> 2) writing compressed midas files (foo.mid.gz) crashes the mlogger when file
> size reaches 2 GBytes. This problem could be new in SL5.1.

(no change)

> 3) when a midas client becomes unresponsive, runs cannot be stopped using the
> "stop" button in mhttpd. This is because cm_transition() loops over all attached
> clients, but never removes clients that are known to be dead. Proposed fix is to
> call cm_check_client() for each client before calling their rpc transition handler.

Fixed in SVN revision 4198, read
http://savannah.psi.ch/viewcvs/trunk/src/midas.c?root=midas&rev=4201&sortby=rev&view=log

> 4) the discussed before fix for reading broken history files (skip bad data).

Fixed in SVN revision 4202, read https://ladd00.triumf.ca/elog/Midas/482

> 5) mhttpd history "export" button needs to be fixed (by request from ALPHA). At
> present it either does not return all exiting data or crashes mhttpd. (no fix)

(no change)

> 6) mhttpd ODB editor in "set value" page, the "cancel" button is broken (needs
> to be corrected for "relative URL").

Apply this patch to src/mhttpd.c

@@ -11156,10 +11190,7 @@
          sprintf(str, "SC/%s/%s", eq_name, group);
          redirect(str);
       } else {
-         strlcpy(str, path, sizeof(str));
-         if (strrchr(str, '/'))
-            strlcpy(str, strrchr(str, '/')+1, sizeof(str));
-         redirect(str);
+         redirect("./");
       }

> 7) mhttpd needs AJAX-style methods for reading and writing ODB. (no fix)

(no change)

K.O.

> > Here is the list of known problems I am aware of and of fixes not yet committed to midas svn:
> > 1) added variable /equiment/foo/common/PerVariableHistory
> 
> corrected in svn revision 4203, read
> http://savannah.psi.ch/viewcvs/trunk/src/mlogger.c?root=midas&rev=4203&sortby=rev&view=log

Was still broken - all should work in revision 4207.

> > 2) writing compressed midas files (foo.mid.gz) crashes the mlogger when file
> > size reaches 2 GBytes. This problem could be new in SL5.1.

It turns out that on SL5 and SL5.1 (and others?) the 32-bit version of ZLIB opens the
compressed output file without the O_LARGEFILE flag, this limits the file size to 2 GB.

Fixed by opening the file ourselves, then attach compression stream using gzdopen().

Revision 4207. (Not tested on Windows - may be broken!)

> > 5) mhttpd history "export" button needs to be fixed (by request from ALPHA). At
> > present it either does not return all exiting data or crashes mhttpd. (no fix)
> 
> (no change)
> 
> > 6) mhttpd ODB editor in "set value" page, the "cancel" button is broken (needs
> > to be corrected for "relative URL").
> 
> Apply this patch to src/mhttpd.c
> 
> @@ -11156,10 +11190,7 @@
>           sprintf(str, "SC/%s/%s", eq_name, group);
>           redirect(str);
>        } else {
> -         strlcpy(str, path, sizeof(str));
> -         if (strrchr(str, '/'))
> -            strlcpy(str, strrchr(str, '/')+1, sizeof(str));
> -         redirect(str);
> +         redirect("./");
>        }
> 
> > 7) mhttpd needs AJAX-style methods for reading and writing ODB. (no fix)
> 
> (no change)
> 
> K.O.

I'm getting segfaults in yb_any_file_rclose (closing a file opened with
yb_any_file_ropen with type MIDAS).

I think there are bugs with freeing from uninitialized pointers my.pmagta,
my.pyh, and my.pylrl (which are only set when opening a YBOS file).  These
should be set to NULL in yb_any_file_ropen (case MIDAS).  Likewise, the MIDAS
format pointers my.pmp and my.pmrd should be NULLed for YBOS opens. 

It might be wise to also initialize the pointers in the "my" structure to null.

--Donald              

> I'm getting segfaults in yb_any_file_rclose (closing a file opened with
> yb_any_file_ropen with type MIDAS).
> 
> I think there are bugs with freeing from uninitialized pointers my.pmagta,
> my.pyh, and my.pylrl (which are only set when opening a YBOS file).  These
> should be set to NULL in yb_any_file_ropen (case MIDAS).  Likewise, the MIDAS
> format pointers my.pmp and my.pmrd should be NULLed for YBOS opens. 
> 
> It might be wise to also initialize the pointers in the "my" structure to null.

Do you see this crash even after my fix to (another?) double free?

K.O.

Hi all,

I'm currently trying to see if I can speed up polling in a frontend I'm testing. 
Currently it seems like I can't get 'lam's to happen faster than 120 times/second. 
There must be a way to make this faster. From what I understand, changing the poll 
time (500ms by default) won't affect the frequency of polling just the 'lam' 
period.

Any suggestions?

Thanks for your help!

Isaac

Hi,

What is the actual readout time, event size?
Do you have multiple equipment and of what type if any?

PAA

> 
> I'm currently trying to see if I can speed up polling in a frontend I'm testing. 
> Currently it seems like I can't get 'lam's to happen faster than 120 times/second. 
> There must be a way to make this faster. From what I understand, changing the poll 
> time (500ms by default) won't affect the frequency of polling just the 'lam' 
> period.
> 
> Any suggestions?
> 

You could switch from the traditional midas mfe.c frontend to the C++ TMFE frontend,
where all this "lam" and "poll" business is removed.

At the moment, there are two example programs using the C++ TMFE frontend,
single threaded (progs/fetest_tmfe.cxx) and multithreaed (progs/fetest_tmfe_thread.cxx).

K.O.

> Hi all,
> 
> I'm currently trying to see if I can speed up polling in a frontend I'm testing. 
> Currently it seems like I can't get 'lam's to happen faster than 120 times/second. 
> There must be a way to make this faster. From what I understand, changing the poll 
> time (500ms by default) won't affect the frequency of polling just the 'lam' 
> period.
> 
> Any suggestions?
> 
> Thanks for your help!
> 
> Isaac

Hi,

How many equipment do you have and of what type?
What is the measured readout time of your equipment?

As you mentioned the polling time define the maximum time you spend in the in polling call before checking other equipment and system activities. But as soon as you get a LAM during the polling loop, the event is readout. The readout time of this equipment is obviously to be considered as well.

In case you have multiple equipment, the readout time of the other equipment is to be taken in account as you wont return to your polling prior the completion of them.

Something must be wrong on your side. If you take the example frontend under

midas/examples/experiment/frontend.cxx

and let it run to produce dummy events, you get about 90 Hz. This is because we have a

  ss_sleep(10);

in the read_trigger_event() routine to throttle things down. If you remove that sleep, 
you get an event rate of about 500'000 Hz. So the framework is really quick.

Probably your routine which looks for a 'lam' takes really long and should be fixed.

Stefan

> Something must be wrong on your side. If you take the example frontend under
> 
> midas/examples/experiment/frontend.cxx
> 
> and let it run to produce dummy events, you get about 90 Hz. This is because we have a
> 
>   ss_sleep(10);
> 
> in the read_trigger_event() routine to throttle things down. If you remove that sleep, 
> you get an event rate of about 500'000 Hz. So the framework is really quick.
> 
> Probably your routine which looks for a 'lam' takes really long and should be fixed.
> 
> Stefan

Sorry if I am going off-topic but, because the ss_sleep function was mentioned here, I 
would like to take the chance and report an issue that I am having.

In all my slow control frontends, the CPU usage for each frontend is close to 100%. This 
means that each frontend is monopolizing a single core. When I did some profiling, I 
noticed that 99% of the time is spent inside the ss_sleep function. Now, I would expect 
that the ss_sleep function should not require any CPU usage at all or very little.

So my two questions are:
Is this a bug or a feature?
Would you able to check/reproduce this behavior or do you need additional info from my 
side?

> Something must be wrong on your side. If you take the example frontend under
> 
> midas/examples/experiment/frontend.cxx
> 
> and let it run to produce dummy events, you get about 90 Hz. This is because we have a
> 
>   ss_sleep(10);
> 
> in the read_trigger_event() routine to throttle things down. If you remove that sleep, 
> you get an event rate of about 500'000 Hz. So the framework is really quick.
> 
> Probably your routine which looks for a 'lam' takes really long and should be fixed.
> 
> Stefan

Hi Stefan,

I should mention that I was using midas/examples/Triumf/c++/fevme.cxx. I was trying to see 
the max speed so I had the 'lam' always = 1 with nothing else to add overhead in the 
poll_event(). I was getting <200 Hz. I am assuming that this is a bug. There is no 
ss_sleep() in that function.

Thanks for your quick response!

Isaac