Jason Sachs wrote:
From what I understand about Boost shared memory segments, they are not infinitely growable, so I think I have to organize my data into chunks of a more reasonable size, and allocate a series of separate shared memory segments with a few chunks in each. (there are other application-specific reasons for me to do this anyway) So I am trying to figure out what is a reasonable size is of shared memory to allocate. (probably in the 64K - 1MB range but I'm not sure)
Does anyone have any information about the overhead of a shared memory segment? Just an order of magnitude estimate, e.g. M bytes fixed + N bytes per object allocated + total size of names. Are M,N on the order of 10 bytes or 10Kbytes or what?
If you mean the overhead added by a named allocation and indexes, use managed_shared_memory.get_free_memory() function to know how many bytes you have after creating the managed segment and after creating an empty vector. Take in care that if you fill those vectors alternatively, the reallocations needed by the vector might not take advantage of all the needed memory (one vector can end just in the middle of the segment and the other vector just can't take the memory before and after that vector). If you need to minimize needed shared memory, pre-calculate all the data and then dump it in shared memory. Regards, Ion