Hey there, What does the metric about server mappe...
# general
Hey there, What does the metric about server mapped memory usage refers to? The servers are using 20Gb total (according to k9s and grafana) but that metric states that more than 30gb has been mapped. I’m confused. (I don't have too much exp with ops)
Some will certainly provide a better explanation than I do but the idea is that pinot servers heavily leverages off heap with paging caching. This feature of Java allows to access files on the FS as if they where in memory. The metrics basically tells you how much of your indexed data is being served by this mechanism.
So it’s decoupled from the heap.
What Daniel said is spot on. It's a metric telling you how much data is `mmap`'d. One of the best explanations I've seen so far is https://xunnanxu.github.io/2016/09/10/It-s-all-about-buffers-zero-copy-mmap-and-Java-NIO/
So it is telling me how much storage from the file system it consumed? Because the numbers don't add up to be the amount of ram being used
AFAIK, yes. I just checked, one of our OFFLINE servers has 2.85T mmap’ed. Certainly this would come from the FS.
mmaped files is not related to ram usage
It tells you how much data sitting on disk is served by memory mapped files
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Nice, thanks!!!