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

[Michal Nazarewicz]

On Thu, Dec 29 2016, Eric Anholt wrote:
> Michal Hocko <mhocko@xxxxxxxxxx> writes:
>
>> This has been already brought up
>> http://lkml.kernel.org/r/20161130092239.GD18437@xxxxxxxxxxxxxx and there
>> was a proposed patch for that which ratelimited the output
>> http://lkml.kernel.org/r/20161130132848.GG18432@xxxxxxxxxxxxxx resp.
>> http://lkml.kernel.org/r/robbat2-20161130T195244-998539995Z@xxxxxxxxxxxxxxxxxx
>>
>> 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.

Sounds like a regression which should be fixed.

This is why I donât think removing the message is a good idea.  If you
suddenly see a lot of those messages, something changed for the worse.
If you remove this message, you will never know.

> However, if this is an expected path during normal operation,

This depends on your definition of âexpectedâ and ânormalâ.

In general, I would argue that the fact those ever happen is a bug
somewhere in the kernel â if memory is allocated as movable, it should
be movable damn it!

> 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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