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From Peter Schuller <>
Subject Re: better anti OOM
Date Mon, 26 Dec 2011 23:09:26 GMT
> If node is low on memory 0.95+ heap used it can do:
> 1. stop repair
> 2. stop largest compaction
> 3. reduce number of compaction slots
> 4. switch compaction to single threaded
> flushing largest memtable/ cache reduce is not enough

Note that the "emergency" flushing is just a stop-gap. You should run
with appropriately sized heaps under normal conditions; the emergency
flushing stuff is intended to mitigate the effects of having a too
small heap size; it is not expected to avoid completely the
detrimental effects.

Also note that things like compaction does not normally contribute
significantly to the live size on your heap, but it typically does
contribute to allocation rate which can cause promotion failures or
concurrent mode failures if your heap size is too small and/or
concurrent mark/sweep settings not aggressive enough. Aborting
compaction wouldn't really help anything other than short-term
avoiding a fallback to full GC.

I suggest you describe exactly what the problem is you have and why
you think stopping compaction/repair is the appropriate solution.

/ Peter Schuller (@scode,

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