RE: Does EPICS Base support multi-thread on vxWorks 6.3?

[lorna.zhang@ni.com]

The delay passed to ca_pend_event is
0.5s.

I changed to call ca_context_create
with ca_enable_preemptive_callback (without any other change... and still
calling ca_pend_event afterwards), and found out the CPU 100% usage issue
was gone. Weird!

Lorna Zhang
National Instruments Shanghai
Tel: 86-21-50509810-3230

From:	"Jeff Hill" <johill@lanl.gov>
To:	<lorna.zhang@ni.com>, "'Andrew Johnson'" <anj@aps.anl.gov>
Cc:	<tech-talk@aps.anl.gov>
Date:	04/19/2011 06:37 AM
Subject:	RE: Does EPICS Base support multi-thread on vxWorks 6.3?

---

Ø  Is
there any other reason that could cause similar issues?

 

What delay is being passed to ca_pend_event?

 

Otherwise, set a breakpoint in the function that uses CPU, to see who calls it, and how often.

 

Jeff

______________________________________________________
Jeffrey O. Hill           Email        johill@lanl.gov
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Los Alamos NM 87545 USA   FAX          505 665 5107

 

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From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of lorna.zhang@ni.com
Sent: Monday, April 18, 2011 2:59 AM
To: Andrew Johnson
Cc: tech-talk@aps.anl.gov
Subject: Re: Does EPICS Base support multi-thread on vxWorks 6.3?

 

I'm not sharing a single CA client context between threads, I did make a call to ca_context_create() with ca_disable_preemptive_callback when a new thread is initiated.

Is there any other reason that could cause similar issues?

Andrew, thanks for your recommendation of using ca_enable_preemptive_callback, but that might not be my first choice.

Lorna

From:	Andrew Johnson <anj@aps.anl.gov>
To:	tech-talk@aps.anl.gov
Cc:	lorna.zhang@ni.com
Date:	04/15/2011 11:07 PM
Subject:	Re: Does EPICS Base support multi-thread on vxWorks 6.3?

 

---

Hi Lorna,

On Friday 15 April 2011 02:34:53 lorna.zhang@ni.com wrote:
>
> We developed a client based on libca (EPICS Base 3.14.9), which will
> create it's own worker thread on construction. But we found it working
> strangely on vxWorks (ppc-603). Whenever a second EPICS client is created
> (meaning there are now 2 EPICS worker threads on vxWorks), the CPU usage
> became 100%.
>
> From the profile, we found the ca_pend_event is consuming lots of the CPU.
>
> Meanwhile, it seems epicsMutex is failing to do the lock for the second
> EPICS client??

EPICS should work fine on your hardware and OS combination, this is probably
an application programming issue.

Are these two threads sharing a single CA client context?  Hopefully Jeff Hill
will respond here too, but you might want to read this and the following
sections of the CA Reference Manual for some ideas:
http://www.aps.anl.gov/epics/base/R3-14/12-docs/CAref.html#Thread
In particular if you're experienced in writing multi-threaded code you might
want to use ca_enable_preemptive_callback mode and completely avoid having to
call ca_pend_event() in your code.

- Andrew
--
An error is only a mistake if you don't learn from it.
When you learn something from it, it becomes a lesson.