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I am getting sum of all reserved memory in KBs by using following command:-

ps aux --sort -rss | awk '{sum +=$6} END {print sum}'
OUTPUT: 14746220 i.e. 14.74GB

However free -g returns 27GB as used. Why there is a difference between the two outputs? Doesn't ps shows all the memory allocation?

Mangat Rai Modi
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I had the exact same situation. htop and top both reported about 95% usage (excluding buffers/caches) as did free -m. When summing up the processes from ps, I only was using about 10% of the memory. I found these sites to be invaluable:

In my case it was the dentries/inode cache that was filling the memory. I don't know why free didn't count these as buffers/cache. You can flush this information with the following command, which does not hurt the system:

echo 3 > /proc/sys/vm/drop_caches

Information about this is detailed here: https://linux-mm.org/Drop_Caches

fidian
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