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

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Date:   Wed, 21 Aug 2019 16:34:47 +0000
From:   Nadav Amit <namit@...are.com>
To:     David Hildenbrand <david@...hat.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 Aug 21, 2019, at 9:29 AM, David Hildenbrand <david@...hat.com> wrote:
> 
> 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. I will post v2 of the patch.