[systemd-devel] How to scale journald correctly?
Lennart Poettering
lennart at poettering.net
Tue Jul 17 09:03:50 UTC 2018
On Di, 17.07.18 09:25, Martin Häcker (mh at sntl-publishing.com) wrote:
> On 13.07.18 17:07, Lennart Poettering wrote:
> > journald is designed to just write out what is being thrown at it,
> > with the speed the underlying device permits. It is using relatively
> > large reception buffers for this, so that clients don't have to stall
> > on journald. If you flood journald heavily it will eventually cause
> > clients to block though.
>
> Is there a known bug about this in version 219? Because what we see is
> that even with a moderate write load of about 100-500 kb / s at some
> point journald seems to snap and starts reading and writing at full disk
> throughput speed (which is about 50mb/s on our servers).
>
> That smells like a bug to me.
>
> As we're using the long term support version fo SystemD in CentOS 7.5, I
> guess that this behavior should be fixed / discussed / workarounds
> documented - but I'm not entirely sure what the right way to proceed
> would be here. Please advise.
>
> For reference, I'm referring to the behavior documented in this bug
> report: https://bugzilla.redhat.com/show_bug.cgi?id=1599658
219 is really old, we don't really focus on that upstream here. I know
that RHEL has backported a number of fixes, but you'd have to enquire
the RHEL/CentOS people about this...
Lennart
--
Lennart Poettering, Red Hat
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