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Update manual to reflect removal of global huge object tree.

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This resolves #323.
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Jason Evans 2016-02-24 14:36:58 -08:00
parent aa63d5d377
commit f591d2611a
1 changed files with 11 additions and 16 deletions
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doc/jemalloc.xml.in
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@ -518,23 +518,18 @@ for (i = 0; i < nbins; i++) {
common case, but it increases memory usage and fragmentation, since a common case, but it increases memory usage and fragmentation, since a
bounded number of objects can remain allocated in each thread cache.</para> bounded number of objects can remain allocated in each thread cache.</para>
<para>Memory is conceptually broken into equal-sized chunks, where the <para>Memory is conceptually broken into equal-sized chunks, where the chunk
chunk size is a power of two that is greater than the page size. Chunks size is a power of two that is greater than the page size. Chunks are
are always aligned to multiples of the chunk size. This alignment makes it always aligned to multiples of the chunk size. This alignment makes it
possible to find metadata for user objects very quickly.</para> possible to find metadata for user objects very quickly. User objects are
broken into three categories according to size: small, large, and huge.
<para>User objects are broken into three categories according to size: Multiple small and large objects can reside within a single chunk, whereas
small, large, and huge. Small and large objects are managed entirely by huge objects each have one or more chunks backing them. Each chunk that
arenas; huge objects are additionally aggregated in a single data structure contains small and/or large objects tracks its contents as runs of
that is shared by all threads. Huge objects are typically used by
applications infrequently enough that this single data structure is not a
scalability issue.</para>
<para>Each chunk that is managed by an arena tracks its contents as runs of
contiguous pages (unused, backing a set of small objects, or backing one contiguous pages (unused, backing a set of small objects, or backing one
large object). The combination of chunk alignment and chunk page maps large object). The combination of chunk alignment and chunk page maps makes
makes it possible to determine all metadata regarding small and large it possible to determine all metadata regarding small and large allocations
allocations in constant time.</para> in constant time.</para>
<para>Small objects are managed in groups by page runs. Each run maintains <para>Small objects are managed in groups by page runs. Each run maintains
a bitmap to track which regions are in use. Allocation requests that are no a bitmap to track which regions are in use. Allocation requests that are no