[foreign-jextract] RFR: MemorySegmentPool + Allocator

[Maurizio Cimadamore]

On Sat, 17 Apr 2021 20:53:41 GMT, Radoslaw Smogura <github.com+7535718+rsmogura at openjdk.org> wrote:

> (Preview)
> 
> The MemorySegmentPool is a pool maintaining memory segments, optionally can expose allocator which can be bound to other scope, and which will return allocated segments back to pool.
> 
> However the best results has been achieved by using getSegmentEntry & putSegmentEntry methods.
> 
> The pool is intended to be used by long running applications (i.e. like global shared pool), where fast allocation and de-allocation of segments is critical (was designed during implementation of I/O subsystem with Panama, as a pool for temporary buffers between system I/O methods and Java byte arrays from InputStreams).
> 
> The pool uses hand-made SpinLockQueue as the Deque from JDK offers too much functionality and overhead.

if I remove CAS from the queue (e.g. provide an optimized queue implementation for confined code), results are


Benchmark                      (size)  Mode  Cnt   Score   Error  Units
StrLenTest.panama_strlen_pool       5  avgt   30  52.930 ? 0.643  ns/op
StrLenTest.panama_strlen_pool      20  avgt   30  57.778 ? 0.789  ns/op
StrLenTest.panama_strlen_pool     100  avgt   30  74.229 ? 0.948  ns/op

Which are still not where I'd expected them to be.

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PR: https://git.openjdk.java.net/panama-foreign/pull/509