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<== Date ==> <== Thread ==>
Subject: Re: Slow initial connection using Simple Channel Access
From: Alan Biocca <[email protected]>
To: "Dale L. Brewe" <[email protected]>, [email protected]
Cc: [email protected]
Date: Fri, 09 Apr 1999 12:49:26 -0700
Chris Timossi will likely comment further re NT specifics, but just to give a reference point, these functions make 7,000 successful connections in something less than 2 seconds from Unix on an old Sparc 2. It is important to queue all the requests before processing them, do not do them one at a time. (ie queue everything then one do_get). The interfaces in the underlying Channel Access are significantly optimized for batch processing and SCA uses this. In addition, single requests cause a flurry of packets on the network that can cause tinygrams to impact network performance for hosts and network neighbors without getting much work done.

That having been said, 250-300 msec sounds slow even for individual requests. Possibly a configuration problem.

-- Alan K Biocca

At 09:51 AM 4/9/99 -0500, Dale L. Brewe wrote:
I've been using the Simple Channel Access libraries under NT, and have
noticed that the time to make an initial connection is quite long. For
example, using the routine cache_getbyname, it takes about 45sec to get 140
values initially (~0.33sec/value). I've also tried the batch routines
que_get and do_get, with a marginal improvement (to ~0.25sec/value), which
is still pretty difficult to live with. Can anyone tell me if they have a
similar experience? Is this an inherent limitation of these
functions/library, or is it possible to improve the performance? My ioc
uses epics 3.13beta11 and my client (based on LabVIEW) has used sca3.dll
and ca.dll for 3.13.0 and previous versions.
Thanks
Dale Brewe
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Dale L. Brewe     PNC-CAT/U. of Washington
 ph: 630 252 0582         fax: 630 252 0580
 Mail:
 APS/Argonne National Laboratory
 Bldg 435E sector 20
 9700 S. Cass Ave.
 Argonne, IL 60439
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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