Re: TMapFile opened in update mode ...

From: Otto Schaile (Otto.Schaile@Physik.uni-muenchen.de)
Date: Mon Nov 02 1998 - 13:46:50 MET


On Mon, 2 Nov 1998, Piergiorgio Cerello wrote:

> I would also like to add a question to all rooters concerning shared
> memories.
> I'm filling shared memories in a standalone producer, and I would like to
> reset them from the consumer, when the operator requires it.
> I tried to open the sahred memory  from the consumer in "update" mode, but
> then I couldn't reset the objects (histograms) it contained. 
> I wonder wether it is possible or not...

As I understand things this will not (never) be possible because of the
virtual pointers which are only valid in the producers address space.
We solve this by sending a message to the producer which in turn 
clears the histograms as required.

What we however are more concerned is the fact that one needs two copies
of the histograms in memory, therefore Update() is required. With say
15 Mbyte of histograms this is important with respect to memory and
CPU resources even for 128 MB machine with 300 MHz CPUs. 
So we hope that eventually the producer can directly put the hists
into the shared memory obsoleting the Update().

Cheers
Otto
----------------------------------------------------------------------------
Otto Schaile                    Sektion Physik der LMU Muenchen
Phone: (+49 89)289 14070        Am Coulombwall 1, D-85748 Garching, Germany
FAX:   (+49 89)289 14072        EMail: Otto.Schaile@Physik.Uni-Muenchen.DE



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