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An interesting fact is that the hotspot team went back on their 20-year conviction that load-barriers reduce performance too much. I guess improvements in CPU
by ryanobjc 8y ago
An interesting fact is that the hotspot team went back on their 20-year conviction that load-barriers reduce performance too much. I guess improvements in CPU and VM designs has changed their minds.
This is a big deal, and a major departure.
I'm hoping this will improve things, this new architecture more closely resembles Azul's C4. Java and large heaps with non-conforming object allocation patterns (medium aged objects are the most troublesome) sucks really badly.
- repolfx 8y agoThey do reduce performance a lot. I think what changed is there are now classes of customers who are willing to take a huge performance hit for reliably low pause times or reliably huge heaps. Whereas in the past heaps were smaller and perhaps latency tails were something people cared about less.
- ADefenestrator 8y agoG1 does a lot better here in my (somewhat limited) experience. There's some overhead, and you have to give it some extra space, but the mixed collections are decent at making their way through medium-aged objects that survived to the old generation. Still nowhere close to 5-10ms though, and with a fair bit of memory bandwidth burned copying it through the survivor spaces.