On 2016-01-04 Hartmut W Sager wrote:
I am surprised. Doesn't a current high-grade OS like Linux (maybe not Windows) routinely close the gaps in RAM by relocating running code and data? This is quite efficiently do-able in CPU architectures
I just read an article about this. Supposedly modern linux (not sure about RHEL6) does mem "defrag" only on oom condition (going from vague memory). Discussions always crop up about having a kthread that can do periodic defrag outside of oom condition but I don't think this is being done at present.
Defrag on oom does sound like what I just saw today, because when the oom happened there was almost no contig ram left, but when I checked the server a while later there were lots of bigger contigs, but still not enough for a 4G alloc.