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0 pointsRoark662y ago0 comments

I quite like containers to limit/reserve the ram/cpu use for certain processes. For example imagine a tiny service used by Few concurrent users that needs a SQL db, a app server, and a reverse proxy (For ssl/caching) in front. I'm quite happy to put stuff like this on a tiny VM with 1vCPU and 1GB RAM. Mnthly cost ~$5 for compute. I typically reserve/limit 64MB/128MB for nginx, 384mb/512mb for mariadb, and 256mb/384mb for the app server (PHP etc).Also I have cpu share reservation/limits too. Of course it requires tuning the configs, but it runs great(verified with load testing and actual use). If you put the same software on the same host with no reservations/limits there are situations where latencies grow a lot or the whole thing freezes because one component consumes too much resources. If anyone knows any non-container lie overhead ways to partition a single vcpu and a gig of ram like this I'd be interested to hear about it.

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predakanga2y ago

Systemd has a mechanism[0] for configuring those limits.

I believe you can limit a unit to 1 vCPU and 256MB of memory by using something like the following:

[Service]

CPUQuota=100% # 100% of a core

MemoryLimit=256MB

Red Hat has some documentation[1] as well if the systemd stuff is too oblique.

[0]: https://www.freedesktop.org/software/systemd/man/systemd.res...

[1]: https://access.redhat.com/documentation/en-us/red_hat_enterp...

topspin2y ago

> If anyone knows any non-container lie overhead ways to partition a single vcpu and a gig of ram like this I'd be interested to hear about it.

You can use cgroups[1] to do this, because that's what your container runtime is doing. People don't know this because they think these features have something to do with their container runtime and that's what they use, so no one discovers it.

Plus, the user facing tools for cgroups are slightly hideous. And that won't ever get fixed for the reasons previously stated. Sigh.

Also, I'm sure a lot of people would appreciate learning about your tuning techniques, containers or otherwise. Consider writing it up.

[1] circa 2007...

ilyt2y ago

You can set up same limits via systemd units as they are using same interfaces as containers. They can be set up via systemd overrides to existing services so they are pretty straightforward

Just be beware of same problems like swap trap (limiting only memory and not memory and swap will just make apps hitting the memory limit start to swap like hell)

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