Re: [Metakit] RAM usage

[Tom Krehbiel]

If the heap is being used to store record modification the it is 
possible that MetaKit is fragmenting the heap. It's been a long 
time since I looked at this issue but I'm pretty sure this will 
generate performance issues and I think it will also create RAM 
usage issues because of the minimum block size managed by the 
malloc command.

Tom Krehbiel

I think  the assumption that a commit would follow shortly after
modification is not in general valid.  In the application I am currently
working on, there is a point at which there will be a considerable number
of access/modify actions prior to the next commit.
--------------------------------------
Gary H. Merrill
Director and Principal Scientist, New Applications
Data Exploration Sciences
GlaxoSmithKline Inc.
(919) 483-8456
                                                                                                                        
                      "Jacob Levy"                                                                                      
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                                               Subject: RE: [Metakit] RAM  usage                                        
                                                                                                                        
                      29-Jan-2004 13:56                                                                                 
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I've often wondered if a more sparse representation of modified data that
*only* contains the modifications would save memory and also give
acceptable lookup performance. Presumably after modification its likely
that a commit will follow shortly, so then it might make sense to penalize
lookups that happen between modifications and commits. Just a thought.

--JYL


for clarification:
MK saves modified columns of data on the heap.  when you commit, it
writes them to the file (via normal i/o or memory mapping, as
appropriate), and then frees that heap space.   so if the file is mapped
(as it will be if it is not huge) the total space in use stays about the
same over a commit.  the virtual space will likely grow, for the first
commit, as the memory allocator likely keeps the freed heap in the
virual space.
--- Jacob Levy <[EMAIL PROTECTED]> wrote:

Bernard

Committing does not free the memory. As I said before, Metakit maps
the *entire file* into memory. So if the file grows, so does the
memory mapping requirement. Whether the physical RAM used by the
program grows or not is a factor influenced by the OS, not by Metakit.
--JYL


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