G1 feedback: adaptive size problems ?
sbordet at intalio.com
Mon Apr 30 06:15:50 PDT 2012
using JDK 1.7.0_04, Ubuntu Linux 12.04 64 bit, attached you can find
the GC log of my Java IDE.
I noticed that sometimes G1 performs a "to-space overflow" collections
that last way more than the target pause (in my case, up to 3+
seconds), and that after these kind of pauses the survivor spaces get
a big size reduction (e.g from 64 MiB to 6 MiB), which causes more
"to-space overflow" collections until a Full GC seems to restore
At one point I see in the log this entry:
[Eden: 0B(512M)->0B(512M) Survivors: 0B->0B Heap: 1002M(1024M)->1002M(1024M)]
which seems quite odd to me (no young generation ?) and after that a
Full GC that restores everything (at the cost of 1-2 seconds pause).
I'm going to add -XX:-UseAdaptiveSizePolicy which in the past seemed
to solve these issues.
I just wanted to report my findings, and if someone can shed a light
on what's going on, will be great.
Finally, no matter how good the architecture and design are,
to deliver bug-free software with optimal performance and reliability,
the implementation technique must be flawless. Victoria Livschitz
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