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

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Message-ID: <5BBC6CB3-2DCD-4A95-90C9-7C23482F9B32@vmware.com>
Date:   Wed, 21 Aug 2019 16:23:22 +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 9:05 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.