[systemd-devel] setting cpulimit/iolimit on mysql thread not entire process

[Mantas Mikulėnas]

On Tue, Nov 28, 2023 at 8:27 AM jai <jaimin at webuzo.com> wrote:

> I am able to set cpulimit, iolimit, etc for a process using its pid
> through cgroups v2. But for some threads of a single mysql process, how can
> I achieve that?
>

You cannot; 1) the limits are per-cgroup and the entire service is a single
cgroup; 2) the threads are created by mysqld, not by systemd, and systemd
does not monitor and move service processes across cgroups once the service
is already running; 3) afaik, in cgroups v2 it isn't even allowed for
threads of a single process to straddle multiple cgroups anymore.

I'm not a DBA but I've heard that one common way to handle this would be to
create a separate MySQL instance (probably on a separate machine, even)
that would replicate all the data, for the heavy users to query. (Or the
other way around, main instance for the heavy updates ⇒ replica for regular
queries.)

-- 
Mantas Mikulėnas
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