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Subject: Re: [PATCH v2] mm/balloon_compaction: Informative allocation warnings
To:     Nadav Amit <namit@vmware.com>
Cc:     "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20190821094159.40795-1-namit@vmware.com>
 <75ff92c2-7ae2-c4a6-cd1f-44741e29d20e@redhat.com>
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From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <497b1189-8e1d-2926-ee5e-9077fcceb04b@redhat.com>
Date:   Wed, 21 Aug 2019 21:06:07 +0200
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On 21.08.19 20:59, Nadav Amit wrote:
>> On Aug 21, 2019, at 11:57 AM, David Hildenbrand <david@redhat.com> wrote:
>>
>> On 21.08.19 11:41, Nadav Amit wrote:
>>> There is no reason to print generic warnings when balloon memory
>>> allocation fails, as failures 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.
>>>
>>> Since such warnings can still be useful to indicate that the balloon is
>>> over-inflated, print more informative and less frightening warning if
>>> allocation fails instead.
>>>
>>> Cc: David Hildenbrand <david@redhat.com>
>>> Cc: Jason Wang <jasowang@redhat.com>
>>> Signed-off-by: Nadav Amit <namit@vmware.com>
>>>
>>> ---
>>>
>>> v1->v2:
>>>  * Print informative warnings instead suppressing [David]
>>> ---
>>> mm/balloon_compaction.c | 7 ++++++-
>>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
>>> index 798275a51887..0c1d1f7689f0 100644
>>> --- a/mm/balloon_compaction.c
>>> +++ b/mm/balloon_compaction.c
>>> @@ -124,7 +124,12 @@ EXPORT_SYMBOL_GPL(balloon_page_list_dequeue);
>>> struct page *balloon_page_alloc(void)
>>> {
>>> 	struct page *page = alloc_page(balloon_mapping_gfp_mask() |
>>> -				       __GFP_NOMEMALLOC | __GFP_NORETRY);
>>> +				       __GFP_NOMEMALLOC | __GFP_NORETRY |
>>> +				       __GFP_NOWARN);
>>> +
>>> +	if (!page)
>>> +		pr_warn_ratelimited("memory balloon: memory allocation failed");
>>> +
>>> 	return page;
>>> }
>>> EXPORT_SYMBOL_GPL(balloon_page_alloc);
>>
>> Not sure if "memory balloon" is the right wording. hmmm.
>>
>> Acked-by: David Hildenbrand <david@redhat.com>
> 
> Do you have a better suggestion?
> 

Not really - that's why I ack'ed :)

However, thinking about it - what about moving the check + print to the
caller and then using dev_warn... or sth. like simple "virtio_balloon:
..." ? You can then drop the warning for vmware balloon if you feel like
not needing it.

-- 

Thanks,

David / dhildenb