From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: Re: [PATCH] virtio-balloon: Disable free page hinting/reporting if page poison is disabled Date: Fri, 17 Apr 2020 07:02:13 -0400 Message-ID: <20200417070129-mutt-send-email-mst@kernel.org> References: <20200417044641-mutt-send-email-mst@kernel.org> <0f867029-aef4-72b9-356f-ec25c265db1b@redhat.com> <20200417051223-mutt-send-email-mst@kernel.org> <3447361c-4d07-1785-c59b-8c98ddaebd92@redhat.com> <20200417055217-mutt-send-email-mst@kernel.org> <1823d9be-d175-6cb5-0c7d-8a68d959a0d5@redhat.com> <20200417061815-mutt-send-email-mst@kernel.org> <34f46dfc-be16-d057-0760-3cb7c1d1288a@redhat.com> <20200417062804-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Return-path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: In-Reply-To: Content-Disposition: inline To: David Hildenbrand Cc: Alexander Duyck , Jason Wang , virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On Fri, Apr 17, 2020 at 12:31:14PM +0200, David Hildenbrand wrote: > On 17.04.20 12:29, Michael S. Tsirkin wrote: > > On Fri, Apr 17, 2020 at 12:26:24PM +0200, David Hildenbrand wrote: > >> On 17.04.20 12:19, Michael S. Tsirkin wrote: > >>> On Fri, Apr 17, 2020 at 12:09:38PM +0200, David Hildenbrand wrote: > >>>> > What do you call "hinting ends" though? The fact we put > >>>>> a page in the VQ is not a guarantee that it's been consumed > >>>>> by the hypervisor. > >>>>> > >>>> > >>>> I'd say hinting ends once the hypervisor sets FREE_PAGE_REPORT_S_DON= E. > >>> > >>> Can't find that one anywhere. what did I miss? > >> > >> Sorry, the QEMU implementation is confusing. FREE_PAGE_REPORT_S_DONE i= s > >> translated to VIRTIO_BALLOON_CMD_ID_DONE > >=20 > > Well VIRTIO_BALLOON_CMD_ID_DONE just means "don't give me any > > more hints, I finished migration". > > Guest will stop hinting even without that once it scans all > > free memory. >=20 > Yeah, that's the end of the whole process where you can be sure the host > processed all requests definetly. It's not guaranteed to happen :) Sending an interrupt at the end of each scan doubles the overhead ... > --=20 > Thanks, >=20 > David / dhildenb