[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.

And this is using low level API (this also optimizes the queue by removing CAS):


Benchmark                          (size)  Mode  Cnt   Score   Error  Units
StrLenTest.panama_strlen_pool_low       5  avgt   30  42.199 ? 0.475  ns/op
StrLenTest.panama_strlen_pool_low      20  avgt   30  44.181 ? 0.248  ns/op
StrLenTest.panama_strlen_pool_low     100  avgt   30  60.410 ? 1.280  ns/op

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