Re:GC Tuning Confessions of a Performance Engineer
by TheLoneWolfling on Friday May 29, 2015 @04:44PM
(#9627254)
Except that a TLAB is worse for cache than a stack.
Look at what happens when you call a bunch of small methods that each allocate a couple things. With a stack, everything stays in nice proximity automaticially. With a TLAB, you quickly fill the TLAB, get another one, get another one, and so on.
Effectively: the stack does any garbage collection that can be statically determined for free, keeping data in cache that actually matters, whereas with TLABs you need to wait for it to pass through GC before any of it is reused.
Look at what happens when you call a bunch of small methods that each allocate a couple things. With a stack, everything stays in nice proximity automaticially. With a TLAB, you quickly fill the TLAB, get another one, get another one, and so on.
Effectively: the stack does any garbage collection that can be statically determined for free, keeping data in cache that actually matters, whereas with TLABs you need to wait for it to pass through GC before any of it is reused.