Remove shared from system.memory.state values?

[trask]

Should shared be removed from system.memory.state values?

I'm reviewing the usage naming convention:

Where appropriate, the sum of usage over all attribute values SHOULD be equal to the limit.

and at least on my system, the shared dimensions appears to be double counted:

root@972900a4c455:/# free
               total        used        free      shared  buff/cache   available
Mem:        32847132     2214804    30020716       80216      611612    30172244

doing the math:

32847132 = 2214804 + 30020716 + 611612

cc @open-telemetry/semconv-system-approvers

[mx-psi]

Discussed on January 18th System Semantic Conventions WG meeting, similar to #531 this blocks stability

[ChrsMark]

Yeap, it seems that the shared column of the free command does not contribute to the total. I'm not sure if the implementations follow the same approach though. @braydonk do you have handy how the Collector is doing that?

In general, maybe that metric is also useful for a system but in order to honor the usage naming convention we can make it a separate metric like system.memory.shared or sth?

[braydonk]

@braydonk do you have handy how the Collector is doing that?

Here's the current definition of the state attribute in the hostmetrics receiver: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/receiver/hostmetricsreceiver/internal/scraper/memoryscraper/metadata.yaml#L12

The memory scraper in the hostmetrics receiver right now uses gopsutil, which on Linux uses /proc/meminfo and on Windows uses GlobalMemoryStatusEx.

shared in the free command is the same as Shmem in meminfo. It indeed does not count toward the total, and using it in a sum will double count memory.

GlobalMemoryStatusEx does not report shared memory.

I am in favour of removing it from the list of suggested attributes given the attribute description mentioned above. Moving it to a separate metric sounds fine.

[ChrsMark]

Thank's @braydonk!

@open-telemetry/semconv-system-approvers any thoughts about this?