Experimental Physics and
Industrial Control System

"Mark Rivers" <[email protected]> · Tue, 31 May 2011 06:45:16 -0500

I am posting some messages from a thread Jay Steele, Jeff Hill and I had earlier this month.  Jay is seeing 5 second delays when running caget, and he says he has tracked it down to ca_context_destroy().  He sees it with both the Cygwin and WIN32 builds, but not to all IOCs.

Mark

----- Original Message -----
From: "Mark Rivers" <[email protected]>
To: "Jay Steele" <[email protected]>, "Christian Roehrig" <[email protected]>
Sent: Wednesday, May 4, 2011 3:48:08 PM
Subject: RE: cygwin and DOS caget, caput running slow at end due toca_context_destroy(), option to speed up execution?

Jay,

The plot thickens.  I just tried the same comparison as you.  I am
running caget on my XP machine.

Here is what I get when I access a PV on a vxWorks IOC.  This is also
5.4.2, and is almost certainly the same BSP as Chris.

C:\Temp>echo 15:42:31.61
15:42:31.61

C:\Temp>.\caget_win32-x86.exe 13IDA:m1
13IDA:m1                       -0.25

C:\Temp>echo 15:42:31.75
15:42:31.75

So it only took 0.14 seconds, very fast.

Now I access a PV on a remote Windows 7 machine.

C:\Temp>echo 15:43:52.80
15:43:52.80

C:\Temp>.\caget_win32-x86.exe 13IDDPS1:cam1:Acquire
13IDDPS1:cam1:Acquire          Done

C:\Temp>echo 15:43:57.55
15:43:57.55

So it took 4.75 seconds.  So my results are almost exactly the opposite
of yours, I am getting fast access to vxWorks and very slow access to a
remote Windows machine.

Mark

Hi Chris,
     I see excessive delays (~5 seconds) when I use caget from a Windows XP computer to access EPICS PVs on the VxWorks IOC. I get much better results (~0.05 second) using caget from the Windows XP computer to access EPICS PVs on the soft IOC running on another Windows XP computer. Running caget from a LINUX computer to access EPICS PVs on VxWorks IOC also has minimal delay (~0.05 second).

     We are using the BSP (VxWorks version 5.5.2) for the VxWorks IOC that you provided to us some months ago. Have you ever run caget from a Windows computer to one of your VxWorks systems? If so, did you see the same ~5 second delay?

Thanks,
Jay Steele
Xradia Corporation

Hi Mark,
     I'm running Windows XP version 2002 service pack 3. When I run the test_caget.bat file on a Windows command shell to access a PV on a VxWorks IOC on the same subnet, I get the following:

C:\Program Files\EPICS WIN32 Extensions>echo 10:25:32.22
10:25:32.22
C:\Program Files\EPICS WIN32 Extensions>caget "21:D3:SM:mx:ActPos"
21:D3:SM:mx:ActPos             5001.46
C:\Program Files\EPICS WIN32 Extensions>echo 10:25:36.79
10:25:36.79

So, caget ran for 4.57 seconds on Windows with the caget executable provided with EPICS WIN32 Extensions Version 1.40 (Build 40).

     When I run the same test_caget.bat file on a cygwin command shell to access a PV on a VxWorks IOC on the same subnet, I get the following:

C:\Software\Software\UltraSPX_EPICS\test>echo 10:29:10.57
10:29:10.57
C:\Software\Software\UltraSPX_EPICS\test>caget "21:D3:SM:mx:ActPos"
21:D3:SM:mx:ActPos             5001.46
C:\Software\Software\UltraSPX_EPICS\test>echo 10:29:15.22
10:29:15.22

So, caget ran for 4.25 seconds on cygwin-x86 using the epics/base-3-14-11/bin/cygwin-x85/caget executable. It is clear that the data is obtained right away, but then there is a delay returning from the caget function. I went through the code some weeks ago, and observed that the delay is due to the ca_context_destroy function.

The equivalent of caget that runs on the same Windows computer as part of the MEDM client to get PV data from the same VxWorks IOC does not have these delays.

Cheers,
Jay Steele
Xradia Corporation

________________________________

From: [email protected] on behalf of Ralph Lange
Sent: Tue 5/31/2011 5:07 AM
To: tech-talk
Subject: Re: caget command holds for more than 10 seconds

10 seconds is the default timeout for channels that are not found.

Can you please show the command line you are using and its output? It would also be useful to know which system you are running caget on, and which version of EPICS you are using.

Thanks,
~Ralph

On 31.05.2011 04:17 lailongwei wrote: 

	hi,
	  when I use caget A, though the data has been gotten, it holds for about ten sends untill the command exit.
	This cause problem when I need to caget four PVs, whose sampling at the same time is very important. How can I solve it.
	Thanks!

	2011-05-31 

________________________________

	lailongwei 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System