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SubjectRe: [PATCH v2] mm/balloon_compaction: Informative allocation warnings
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> On Aug 21, 2019, at 12:12 PM, David Hildenbrand <david@redhat.com> wrote:
>
> On 21.08.19 21:10, Nadav Amit wrote:
>>> On Aug 21, 2019, at 12:06 PM, David Hildenbrand <david@redhat.com> wrote:
>>>
>>> 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.
>>
>> Actually, there is already a warning that is printed by the virtue_balloon
>> in fill_balloon():
>>
>> struct page *page = balloon_page_alloc();
>>
>> if (!page) {
>> dev_info_ratelimited(&vb->vdev->dev,
>> "Out of puff! Can't get %u pages\n",
>> VIRTIO_BALLOON_PAGES_PER_PAGE);
>> /* Sleep for at least 1/5 of a second before retry. */
>> msleep(200);
>> break;
>> }
>>
>> So are you ok with going back to v1?
>
> Whoops, I missed that - sorry - usually the warnings scream louder at me :D
>
> Yes, v1 is fine with me!

Thanks, I missed this one too. This change should prevent making users
concerned for no good reason.

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