linux-kernel - Re: [PATCH] mm: Drop "PFNs busy" printk in an expected path.

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Date:   Thu, 29 Dec 2016 09:27:42 -0800
From:   Eric Anholt <eric@...olt.net>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-stable <stable@...r.kernel.org>,
        "Robin H. Johnson" <robbat2@...is-terrarum.net>,
        Michal Nazarewicz <mina86@...a86.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH] mm: Drop "PFNs busy" printk in an expected path.

Michal Hocko <mhocko@...nel.org> writes:

> This has been already brought up
> http://lkml.kernel.org/r/20161130092239.GD18437@dhcp22.suse.cz and there
> was a proposed patch for that which ratelimited the output
> http://lkml.kernel.org/r/20161130132848.GG18432@dhcp22.suse.cz resp.
> http://lkml.kernel.org/r/robbat2-20161130T195244-998539995Z@orbis-terrarum.net
>
> then the email thread just died out because the issue turned out to be a
> configuration issue. Michal indicated that the message might be useful
> so dropping it completely seems like a bad idea. I do agree that
> something has to be done about that though. Can we reconsider the
> ratelimit thing?

I agree that the rate of the message has gone up during 4.9 -- it used
to be a few per second.  However, if this is an expected path during
normal operation, we shouldn't be clogging dmesg with it at all.  So,
I'd rather we go with this patch, that is unless the KERN_DEBUG in your
ratelimit patch would keep it out of journald as well (un-ratelimited,
journald was eating 10% of a CPU processing the message, and I'd rather
it not be getting logged at all).

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