IE> As I recall, when allocating space in the heap for new objects, SBCL
will periodically
IE> ask the OS for more heap memory. Even if the objects are garbage
collected later,
IE> the allocated memory will remain (SBCL never releases heap memory back
to the
IE> OS even if it isn't using most of it). It also asks for new heap space
in increasingly
IE> large chunks much like a hash table.
SBCL allocates a memory chunk of a fixed size, but it is only reserved at
the beginning -- it is a normal behaviour on Linux that memory is actually
allocated only on the first write to a page. So, yes, memory usage (RSS --
Resident Set Size) grows after use, but it does not grow indefinitely. There
is --dynamic-space-size option in SBCL to control heap size.
It makes sense to set --dynamic-space-size to some reasonable value, and
then watch if application dies of memory starvation.
If it does not die, then it is not a leak. Maybe SBCL just does not feel a
need to clean up weak hash table or some memory generations, and if it is
within allocated heap, it has a right to keep them.
IE> It's possible that some of this memory is the shared memory allocated
by BDB - but that can is upper-bounded in the my-config.sexp file and should
be static.
It is also possible that there is a bug in Elephant, somewhere in FFI code
or in functions which do foreign calls.
Technically it is also possible that leak is caused by SBCL itself -- SBCL
has a conservative GC, but it only is a problem in some rare situations,
when you build very long lists, for example, and probably it's not a case
here.
---------------------
(dotimes (i 1000000)
(elephant:get-instances-by-value 'd::TopicIdentificationC 'd::uri
"goethe"))
;--> memory that is not released after operation 29.0 MB
(dotimes (i 1000000)
(elephant:get-instance-by-value 'd::TopicIdentificationC 'd::uri
"goethe"))
;--> memory that is not released after operation 0.1 MB
---------------------
This is pretty interesting, if indeed get-instances-by-value leak and
get-instance-by-value does not, it should be easy to pinpoint the problem.
How many instances does get-instances-by-value return? Is it a long list?
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