Very high memory usage, but not claimed by any process?

Solution 1:

Since you seem to be running I/O related tests (you didn't explain with details what you did with the LVM volumes), is there any chance that the behavior you noticed is related to the natural OS page cache?

I'm thinking about the Linux standard behavior of using (sometimes almost all) available memory (that is, memory that is not reserved by applications) to cache disk regions that were recently accessed, in order to speed up IOs.

Of course, active applications have priority over this cache, so in case a process needs more ram, the cache is dynamically shrinked.

There is a lot of documentation about Linux page cache on the web, here is one.

Solution 2:

I have the same problem, but I checked the kernel parameters located under /proc/sys/vm/ : overcommit_memory = Default 0 overcommit_ratio = Default 50 max_map_count = Default 65530

And in my case the parameter, root of my problems nr_hugepages, i haved the custom value, but change it for default

nr_hugepages = 0

For more information see https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/performance_tuning_guide/s-memory-captun

Sorry for my english :(