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From "Uwe L. Korn (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ARROW-464) C++: More intelligent array growing
Date Sat, 07 Jan 2017 17:13:58 GMT
Uwe L. Korn created ARROW-464:
---------------------------------

             Summary: C++: More intelligent array growing
                 Key: ARROW-464
                 URL: https://issues.apache.org/jira/browse/ARROW-464
             Project: Apache Arrow
          Issue Type: Improvement
          Components: C++
            Reporter: Uwe L. Korn
            Assignee: Uwe L. Korn


Two things to consider:

 * Instead of always growing the memory to twice the size in the Builders, we should consider
1.5 as a growth factor as this still leads to less memory wastage. As the allocation costly
is mostly linear in the number of newly requested pages, this shouldn't be a noticeable impact.
Due to memory below the size of a single page (i.e. 4KiB) not being able to be expanded in
place, we should keep the factor of there.
 * In the case of jemalloc, we can ask the allocator with the function {{nallocx}} for the
size it would actually allocate for the requested size and then allocate this as the new capacity
for the Builder/Buffer/... and not trigger an reallocation as long as the output of {{nallocx}} doesn't
change.



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