[systemd-devel] systemd-cgtop memory utilization display not useful
lennart at poettering.net
Tue Dec 2 15:27:50 PST 2014
On Fri, 14.11.14 20:36, Lutz Vieweg (lvml at 5t9.de) wrote:
> 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.
We use the "memory.usage_in_bytes" value as exposed by the memory
cgroup controller. I think the kernel cgroup maintainers are aware
that it is currently not ideal, and are revisiting what they export
> 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.
Last time I talked about this with Tejun he suggested sticking with
the current attribute, but that the kernel folks would change would it
would actually report to a more useful value.
Lennart Poettering, Red Hat
More information about the systemd-devel