linux-kernel - Re: [PATCH 0/2] vhost: improve livepatch switching for heavily loaded vhost worker kthreads

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Message-ID: <Y9KyVKQk3eH+RRse@alley>
Date:   Thu, 26 Jan 2023 18:03:16 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     "Seth Forshee (DigitalOcean)" <sforshee@...italocean.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        "Seth Forshee (DigitalOcean)" <sforshee@...nel.org>,
        netdev@...r.kernel.org, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] vhost: improve livepatch switching for heavily
 loaded vhost worker kthreads

On Fri 2023-01-20 16:12:20, Seth Forshee (DigitalOcean) wrote:
> We've fairly regularaly seen liveptches which cannot transition within kpatch's
> timeout period due to busy vhost worker kthreads.

I have missed this detail. Miroslav told me that we have solved
something similar some time ago, see
https://lore.kernel.org/all/20220507174628.2086373-1-song@kernel.org/

Honestly, kpatch's timeout 1 minute looks incredible low to me. Note
that the transition is tried only once per minute. It means that there
are "only" 60 attempts.

Just by chance, does it help you to increase the timeout, please?

This low timeout might be useful for testing. But in practice, it does
not matter when the transition is lasting one hour or even longer.
It takes much longer time to prepare the livepatch.

Best Regards,
Petr