Vertx pooled allocator should be the same as Netty

[franz1981]

Currently, in vertx

vert.x/src/main/java/io/vertx/core/buffer/impl/VertxByteBufAllocator.java

Line 25 in adbe976

public static final ByteBufAllocator POOLED_ALLOCATOR = new PooledByteBufAllocator(true);

is NOT reusing the Netty's PooledByteBufAllocator.DEFAULT, causing creation of more thread-local direct buffers and arenas, enlarging the RSS footprint of vertx application, for no reason.

What's the reason behind this choice @vietj?

The reason why it should be changed, is to "ease" the life of users and libraries which allocate Netty direct buffers using the Netty one and can end up allocating new arenas because of this.

If the aforementioned pool re-use the Netty one, clearly is getting some additional contention, but will save memory, which seems a reasonable trade-off.