RE: [PATCH RFC] virtio_balloon: conservative balloon page shrinking

[Wang, Wei W]

On Thursday, February 6, 2020 5:04 PM, Michael S. Tsirkin wrote:
> virtio_balloon_shrinker_count(struct shrinker *shrinker,
> >  					struct virtio_balloon, shrinker);
> >  	unsigned long count;
> >
> > -	count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
> > +	if (conservative_shrinker && global_node_page_state(NR_FILE_PAGES))
> 
> I'd rather have an API for that in mm/. In particular, do we want other
> shrinkers to run, not just pagecache? To pick an example I'm familiar
> with, kvm mmu cache for nested virt?

We could make it extendable:

#define BALLOON_SHRINKER_AFTER_PAGE_CACHE	(1 << 0)
#define BALLOON_SHRINKER_AFTER_KVM_MMU_CACHE	(1 << 1)
...

uint64_t conservative_shrinker;
if ((conservative_shrinker | BALLOON_SHRINKER_AFTER_PAGE_CACHE) && global_node_page_state(NR_FILE_PAGES))
	return 0;

For now, we probably only need BALLOON_SHRINKER_AFTER_PAGE_CACHE.

Best,
Wei