[systemd-devel] systemd-cgtop memory utilization display not useful

[Lutz Vieweg]

Hi,

I noticed that systemd-cgtop in the "memory" column
displays (and uses for sorting) a value that does include
the cache memory somehow attributed to the slice.

This makes little sense, as

a) cache memory is freed when a task requires that
    memory for more important purposes, so cache memory
    utilization never causes OOM-kills to happen

b) it causes usage numbers to be displayed that are
    way beyond the memory.limit_in_bytes, because the
    kernel (for good reason) does utilize more memory
    for caching than what is limited by memory.limit_in_bytes

c) the sorting by "biggest memory user" is weird if
    a slice is sorted first that might contain not a single
    task, but which was associated with a recently running
    task that read some 8 GB file, while another slice
    containing a permanently running task that allocates
    7 GB of RAM is sorted thereafter.

Please reconsider what values systemd-cgtop uses,
"rss" and "rss-huge" from "memory.stat" might be better
candidates than the currently used.

Regards,

Lutz Vieweg