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Message ID: 283     Entry time: 01 Aug 2006
Author: Konstantin Olchanski 
Topic: Bug Fix 
Subject: User-tunable buffer sizes 
By default, MIDAS creates shared memory event data buffers of default size
EVENT_BUFFER_SIZE defined in midas.h and until now making of large data buffers
for high data rate or large event size experiments was complicated.

Now, bm_open_buffer() will try to read the event buffer size from ODB. If
"/Experiment/Buffer Sizes/BUFFER_NAME" of type DWORD exists, it's value is used
as the buffer size, overriding the default value.

For example, to increase the size of the default MIDAS event buffer ("SYSTEM")
to 2000000 bytes, shutdown all MIDAS programs, delete the old .SYSTEM.SHM file
(and the shared memory segment, using ipcrm). Then run odbedit, cd /Experiment,
mkdir "Buffer Sizes", cd "Buffer Sizes", create DWORD SYSTEM, set SYSTEM
2000000. Then start the rest of the MIDAS programs. Check that the buffer has
the correct size by looking at the size of .SYSTEM.SHM and of the shared memory
segment (ipcs).

This method work for all MIDAS buffers, except for ODB, where the size has to be
specified at creation time using the odbedit command "-s" argument.

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