Services memory percentage counts page cache, so database services always sit at 99%

[imc67]

The memory percentage on the Services page counts page cache, so a database service settles at 99% whatever limit you give it. Raise the limit and a few days later it reads 99% again, which makes the number hard to act on.

Here is the postgresql service on a 4 GB limit, straight from its cgroup:

anon              112 MB
file             3915 MB   (inactive_file 2974 MB, reclaimable)
oom_kill            0

docker stats reports 27% for that same container at that same moment, because it subtracts inactive page cache.

The tricky part is that 99% looks identical whether the cache is comfortably full or the container is thrashing. Here it happened to be the latter: the cgroup hit its ceiling 154 times per minute and the container read 117 MB/min from disk. After raising the limit those dropped to 0 and 44 kB/min. Nothing in the percentage told us which of the two situations we were in.

Would it make sense to base the figure on memory.current minus inactive_file, or to show the reclaim and oom counters from memory.events next to it?

[girish]

I think it would make sense not to count the cache. Checking the code...

edit: ok, i see now. We actually explicitly do not count cache for system memory but this check is not done for the containers.

[girish]

Fixed - https://git.cloudron.io/platform/box/-/commit/a3ee1c354cbf6789724d3fda0ad64c87e3c72ba0 . Thanks for reporting.