From the os of the columnstore um node
You can use cpimport to check memory usage as follows:
Why is not cpimport checked in mcsadmin?
Can not you use getSystemMemory to monitor memory trends?

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mcsadmin> getSystemResourceUsage
getsystemresourceusage Fri Jul 6 14:09:37 2018

System Resource Usage per Module

Module 'pm1' Resource Usage

CPU: 27% Usage
Mem: 28744240k total, 4964320k used, 23563784k cache, 17% Usage
Swap: 4194300 k total, 50860k used, 1% Usage
Top CPU Process Users: cpimport.bin 204%, sshd 66%, sftp-server 33%, cpimport 15%, top 3%
Top Memory Process Users: WriteEngineServ 6%, cpimport.bin 4%, mysqld 4%, PrimProc 2%, ExeMgr 1%
Disk Usage: / 29%, /usr/local/mariadb/columnstore/data1 8%

mcsadmin>

[root@EDWPOCDB1 columnstore_tmp_files]# top
top - 14:10:14 up 2 days, 21:45, 8 users, load average: 2.76, 2.50, 2.50
Tasks: 284 total, 1 running, 283 sleeping, 0 stopped, 0 zombie
Cpu(s): 31.2%us, 1.7%sy, 0.0%ni, 64.5%id, 2.6%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 28744240k total, 28523356k used, 220884k free, 75224k buffers
Swap: 4194300k total, 50860k used, 4143440k free, 23581844k cached