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Thu, 3 Dec 2020 17:49:41 +0000 (UTC) Received: from [10.36.113.250] (ovpn-113-250.ams2.redhat.com [10.36.113.250]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0B85960861; Thu, 3 Dec 2020 17:49:39 +0000 (UTC) Subject: Re: [PATCH 2/2] hv_balloon: do adjust_managed_page_count() when ballooning/un-ballooning To: Vitaly Kuznetsov , linux-hyperv@vger.kernel.org Cc: Wei Liu , Stephen Hemminger , Haiyang Zhang , Michael Kelley , Dexuan Cui , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20201202161245.2406143-1-vkuznets@redhat.com> <20201202161245.2406143-3-vkuznets@redhat.com> <9202aafa-f30e-4d96-72a9-3ccd083cc58c@redhat.com> <871rg6ok4v.fsf@vitty.brq.redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <13524c28-dfec-dd21-8a45-216b161deb72@redhat.com> Date: Thu, 3 Dec 2020 18:49:39 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <871rg6ok4v.fsf@vitty.brq.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 03.12.20 18:49, Vitaly Kuznetsov wrote: > David Hildenbrand writes: > >> On 02.12.20 17:12, Vitaly Kuznetsov wrote: >>> 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'. >>> >>> Suggested-by: David Hildenbrand >>> Signed-off-by: Vitaly Kuznetsov >>> --- >>> drivers/hv/hv_balloon.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c >>> index da3b6bd2367c..8c471823a5af 100644 >>> --- a/drivers/hv/hv_balloon.c >>> +++ b/drivers/hv/hv_balloon.c >>> @@ -1198,6 +1198,7 @@ static void free_balloon_pages(struct hv_dynmem_device *dm, >>> __ClearPageOffline(pg); >>> __free_page(pg); >>> dm->num_pages_ballooned--; >>> + adjust_managed_page_count(pg, 1); >>> } >>> } >>> >>> @@ -1238,8 +1239,10 @@ static unsigned int alloc_balloon_pages(struct hv_dynmem_device *dm, >>> split_page(pg, get_order(alloc_unit << PAGE_SHIFT)); >>> >>> /* mark all pages offline */ >>> - for (j = 0; j < alloc_unit; j++) >>> + for (j = 0; j < alloc_unit; j++) { >>> __SetPageOffline(pg + j); >>> + adjust_managed_page_count(pg + j, -1); >>> + } >>> >>> bl_resp->range_count++; >>> bl_resp->range_array[i].finfo.start_page = >>> >> >> I assume this has been properly tested such that it does not change the >> system behavior regarding when/how HyperV decides to add/remove memory. >> > > I'm always reluctant to confirm 'proper testing' as no matter how small > and 'obvious' the change is, regressions keep happening :-) But yes, > this was tested on a Hyper-V host and 'stress' and I observed 'free' > when the balloon was both inflated and deflated, values looked sane. That;s what I wanted to hear ;) -- Thanks, David / dhildenb