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

[Demi Marie Obenour]

On Tue, Nov 28, 2023 at 08:35:29AM +0200, Mantas Mikulėnas wrote:
> 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.)

Generally heavy analytical queries should be on a replica.  The reason
is that analytical queries are less likely to need the very latest
data, whereas transactions probably do.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/systemd-devel/attachments/20231128/0e9ff764/attachment.sig>