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I believe this is why you sometimes see recommendations to no to set the JVM heap larger than 32 Gigs. Is this still the case though? Does JVM performance fall
by bogomipz 8y ago
I believe this is why you sometimes see recommendations to no to set the JVM heap larger than 32 Gigs.
Is this still the case though? Does JVM performance fall off a cliff without compressed pointers? Or is the issue more GC beyond 32 Gigs.
- lmm 8y agoThe advice I've heard is that there's no point setting a heap size between 32G and 48G: between those limits the bigger object references will cost you more space than you gain. Long pauses for full GC are a distinct issue that large heaps have. I believe the newer garbage collectors are designed to address this, but don't have much experience with them in practice.
- joemag 8y agoPerformance hit is barely noticeable for most apps. The biggest surprise is usually heap usage increase. You can increase your heap from 28 to 34 GB, and end up with less free memory.
- user5994461 8y agoA common misconception unfortunately. The heap is limited to roughly 30 GB, plus a bit of overhead. You will never run in 32bits mode if you set a 32GB heap, because overhead. From experience, a 30GB heap is similar to a 40GB in usable space. 32 vs 64 bits pointers respectively.
- bogomipz 8y agoSorry what is the common misconception? Exceeding a 32 gig heap size will cause the JVM to stop using compressed pointers? This seems to be widely accepted: https://www.elastic.co/guide/en/elasticsearch/guide/current/heap-sizing.html https://www.elastic.co/guide/en/elasticsearch/guide/current/... I understand there's overhead I wasn't suggesting that all 32 Gigs were useable