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From "Ryan Bloom" <...@covalent.net>
Subject RE: APR pool maintains too much free list
Date Mon, 28 Jan 2002 14:44:35 GMT
> I noticed this while looking at Subversion issue #602.  It
> is about Subversion consuming too much memory when importing
> large tree.
> http://subversion.tigris.org/issues/show_bug.cgi?id=602
> 
> I found that memory consumption doesn't go too high if I
> compiled APR with --enable-pool-debug so I glanced
> memory/unix/apr_pools.c.  There I found that non-DEBUG build
> does not free any memory unless the pool holding the
> allocator is destroyed or cleared.  I think it should free
> memory if it already has enough memory in free list.

This is the point of pools.  The idea is that you should hit a steady
state quickly.  Basically, one request goes through, and it allocates
all of the memory out of pools.  The next time that same request is
sent, it should use the same amount of memory.  For all other requests,
it should either use a little more or a little less memory, but at some
point you will get a request that uses more memory than any other
request, and that is how large your pool will be forever, which means
that you will no longer allocate memory.

If your pools are growing too large, then you most likely need to split
the allocation into multiple sub-pools, so that the memory is returned
and can be used by later operations.

Ryan



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