linux-kernel - Re: [PATCH v6 2/2] Unify how inflated memory is accounted in virtio balloon driver

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Message-ID: <8ee986d7-0e3e-6b66-8c13-61fc70fa538e@redhat.com>
Date:   Mon, 1 Aug 2022 17:13:17 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Alexander Atanasov <alexander.atanasov@...tuozzo.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>
Cc:     kernel@...nvz.org, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/2] Unify how inflated memory is accounted in virtio
 balloon driver

On 26.07.22 16:10, Alexander Atanasov wrote:
> Always account inflated memory as used for both cases - with and
> without deflate on oom. Do not change total ram which can confuse
> userspace and users.

Sorry, but NAK.

This would affect existing users / user space / balloon stats. For example
HV just recently switch to properly using adjust_managed_page_count()


commit d1df458cbfdb0c3384c03c7fbcb1689bc02a746c
Author: Vitaly Kuznetsov <vkuznets@...hat.com>
Date:   Wed Dec 2 17:12:45 2020 +0100

    hv_balloon: do adjust_managed_page_count() when ballooning/un-ballooning
    
    Unlike virtio_balloon/virtio_mem/xen balloon drivers, Hyper-V balloon driver
    does not adjust managed pages count when ballooning/un-ballooning and this leads
    to incorrect stats being reported, e.g. unexpected 'free' output.
    
    Note, the calculation in post_status() seems to remain correct: ballooned out
    pages are never 'available' and we manually add dm->num_pages_ballooned to
    'commited'.


-- 
Thanks,

David / dhildenb