Re: Gateway and EPICS_CA_MAX_ARRAY_BYTES

[Dirk Zimoch <dirk.zimoch@psi.ch>]

Hi Pete,

at SLS, we are using the gateway and have several problems.

Leicester, PJ (Pete) wrote:
> No responses to my last email regarding large transfers through the
> Gateway. I'd still like to get an idea of any potential problems in this
> area so two questions:-
>
> 1) Is anyone doing large transfers through the gateway?
> 2) Has anyone tried large transfers and had problems?

Once, someone tried to read camera pictures through the gateway. The 
result was that the gateway hung. It used up all cpu time but the 
thoughput was zero. All clients disconencted.

On the gateway machine, EPICS_CA_MAX_ARRAY_BYTES was not set.

Setting EPICS_CA_MAX_ARRAY_BYTES big enough seemed to help, but you 
can't know in advance how big "big enough" is. At least not on a generic 
system like a gateway. Thus, the EPICS_CA_MAX_ARRAY_BYTES mechanism is 
not really usable.

Since I already have so many other problems with the gateway, I disabled 
access to the camera pictures. I did not try to run performance tests.

I am using the same versions of gateway and base as you do on the 
gateway machine.

Best regards,
Dirk

> Pete Leicester
> Diamond Light Source Ltd.
> Tel: 44 1235 778478
>
>
> -----Original Message-----
> From: Leicester, PJ (Pete) [mailto:peter.leicester@diamond.ac.uk] 
> Sent: 01 August 2005 10:57
> To: tech-talk@aps.anl.gov
> Subject: Gateway and EPICS_CA_MAX_ARRAY_BYTES
>
>
> I have been trying to get a gateway running doing large transfers
> (EPICS_CA_MAX_ARRAY_BYTES=3000000) but I am seeing performance problems.
>
> I can get everything to work but only by restarting the gateway AFTER I
> have booted the IOC and started the EDM client. In the working state the
> Gateway clientEventRate/clientPostRate/serverEventRate/serverPostRate
> are all at around 60Hz. If I then close the EDM client and restart it
> the Gateway runs very slow, the event rate drops down to about 6 Hz
> occasionally rising to 16Hz but it never recovers. If I reboot the
> gateway without touching the IOC or EDM client I get back to the 60Hz
> rate. At all times the event to post rates are much the same (i.e.
> clientEventRate=clientPostRate and  serverEventRate=serverPostRate). I
> only have 40 PV's in total, the gateway appears lightly loaded even when
> running slow (loopRate=260,cpuFraction=0.06,load=0.05).
>
> My test setup is as follows:
> Client EDM screen running on linux/epics 3.14.6
> Gateway version 2.0.0.0Beta18 running on linux/EPICS 3.14.7 cvs snapshot
> taken on 14th April 05. IOC running Vxworks/EPICS 3.14.6 All have
> EPICS_CA_MAX_ARRAY_BYTES=3000000 and the Client and Gateway both have
> EPICS_CA_AUTO_ADDRESS_LIST=NO.
>
> My questions are:-
> 1) Has anyone got large transfers to work reliably? 
> 2) Should I be able to do large transfers with this setup? 
> 3) Has anyone seen this problem before and what is going on when the
> gateway is running slow?
>
> Pete Leicester
> Diamond Light Source Ltd.
> Tel: 44 1235 778478

--
Dr. Dirk Zimoch
Swiss Light Source
Paul Scherrer Institut
Computing and Controls
phone +41 56 310 5182
fax   +41 56 310 4413