Pooling of direct ByteBuffer

[Derek]

Sending along to netty-users which might be a wider audience.

On Thu, May 13, 2010 at 2:10 PM, Derek <deminix at gmail.com> wrote:

> I see that DirectChannelBufferFactory.java is reducing the number of direct
> ByteBuffer allocations and deallocations and I could see how that would be
> helpful but I don't see how it handles all shortcomings of JVM direct
> memory.  Given the number of references to a part of these large direct
> buffers (all the small slices), it seems likely that the large buffer will
> survive young generation collection simply because one of the small slices
> does, and be kept around until an old generation collection.
>
> If old generation collections are infrequent there may be quite a few of
> these around, so it doesn't seem to guard against hitting the max direct
> memory limit and/or limiting c heap use.  Are there reasons that normalizing
> allocation request sizes and direct bytebuffer pooling isn't done?  Was it
> previously done but abandoned in favor of this?  I'm asking because we are
> moving from an internal i/o library to Netty and this is how we currently
> handle direct buffers.  Netty is in many ways superior, but I want to make
> sure we don't regress on what was previously a hard learned lesson.
>
> Thanks.
>
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