linux-kernel - Re: [PATCH] mm/balloon_compaction: suppress allocation warnings

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Date:   Wed, 21 Aug 2019 18:29:04 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Nadav Amit <namit@...are.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/balloon_compaction: suppress allocation warnings

On 21.08.19 18:23, Nadav Amit wrote:
>> On Aug 21, 2019, at 9:05 AM, David Hildenbrand <david@...hat.com> wrote:
>>
>> On 20.08.19 11:16, Nadav Amit wrote:
>>> There is no reason to print warnings when balloon page allocation fails,
>>> as they are expected and can be handled gracefully.  Since VMware
>>> balloon now uses balloon-compaction infrastructure, and suppressed these
>>> warnings before, it is also beneficial to suppress these warnings to
>>> keep the same behavior that the balloon had before.
>>
>> I am not sure if that's a good idea. The allocation warnings are usually
>> the only trace of "the user/admin did something bad because he/she tried
>> to inflate the balloon to an unsafe value". Believe me, I processed a
>> couple of such bugreports related to virtio-balloon and the warning were
>> very helpful for that.
> 
> Ok, so a message is needed, but does it have to be a generic frightening
> warning?
> 
> How about using __GFP_NOWARN, and if allocation do something like:
> 
>   pr_warn(“Balloon memory allocation failed”);
> 
> Or even something more informative? This would surely be less intimidating
> for common users.
> 

ratelimit would make sense :)

And yes, this would certainly be nicer.

-- 

Thanks,

David / dhildenb