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Date:   Wed, 17 Jul 2019 07:20:33 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Alexander Duyck <alexander.duyck@gmail.com>
Cc:     wei.w.wang@intel.com, Nitesh Narayan Lal <nitesh@redhat.com>,
        kvm list <kvm@vger.kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Dave Hansen <dave.hansen@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Yang Zhang <yang.zhang.wz@gmail.com>, pagupta@redhat.com,
        Rik van Riel <riel@surriel.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        lcapitulino@redhat.com, Andrea Arcangeli <aarcange@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>, dan.j.williams@intel.com,
        Alexander Duyck <alexander.h.duyck@linux.intel.com>
Subject: use of shrinker in virtio balloon free page hinting
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Wei, others,

ATM virtio_balloon_shrinker_scan will only get registered
when deflate on oom feature bit is set.

Not sure whether that's intentional.  Assuming it is:

virtio_balloon_shrinker_scan will try to locate and free
pages that are processed by host.
The above seems broken in several ways:
- count ignores the free page list completely
- if free pages are being reported, pages freed
  by shrinker will just get re-allocated again

I was unable to make this part of code behave in any reasonable
way - was shrinker usage tested? What's a good way to test that?

Thanks!

-- 
MST