Linux Virtualization - Feb 2020 - [PATCH RFC] virtio_balloon: conservative balloon page shrinking

On Thursday, February 6, 2020 5:10 PM, David Hildenbrand
wrote:
> so dropping caches (echo 3 > /proc/sys/vm/drop_caches) will no longer
> deflate the balloon when conservative_shrinker=true?
> 
Should be. Need Tyler's help to test it.

Best,
Wei

On 06.02.20 10:28, Wang, Wei W wrote:
> On Thursday, February 6, 2020 5:10 PM, David Hildenbrand wrote:
>> so dropping caches (echo 3 > /proc/sys/vm/drop_caches) will no
longer
>> deflate the balloon when conservative_shrinker=true?
>>
> 
> Should be. Need Tyler's help to test it.
> 
If the page cache is empty, a drop_slab() will deflate the whole balloon
if I am not wrong.

Especially, a echo 3 > /proc/sys/vm/drop_caches

will first drop the page cache and then drop_slab()

While I like the general idea, it looks more like a hack to me, to try
to teach the shrinker something it was not built for/does not support yet.

-- 
Thanks,

David / dhildenb

On Thursday, February 6, 2020 5:32 PM, David Hildenbrand
wrote:
> 
> If the page cache is empty, a drop_slab() will deflate the whole balloon if
I
> am not wrong.
> 
> Especially, a echo 3 > /proc/sys/vm/drop_caches
> 
> will first drop the page cache and then drop_slab()
Then that's the problem of "echo 3 > /proc/sys/vm/drop_cache"
itself. It invokes other shrinkers as well (if considered an issue), need to be
tweaked in the mm.

Best,
Wei