I am analysing all the vsftpd processes using top | grep ‘vsftpd’ but the res value is not changing?
one of the possibilities can be that the file being transferred is relatively small size. You can try going through then below query if the problem persists.
Not all versions will show much fluctuations in the memory usage.
Try to save the memory value of each version’s upload/download and see if any of the version is showing a disproportionate variation in memory usage WHEN FILES ARE TRANSFERRED.
And to be able to see this(unless you are logging the resource usage into some file - still hard as small files in order of MB get transferred mostly less than a sec) as @Sakshat-Crio.Do suggested monitor the resource usage when transferring larger files.
set the refresh rate of the top command to 1
see this for references
and then monitor the res value
make sure you are monitoring the correct process