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[79.176.6.42]) by smtp.gmail.com with ESMTPSA id 200sm1025334wme.32.2019.11.18.14.52.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Nov 2019 14:52:59 -0800 (PST) Date: Mon, 18 Nov 2019 17:52:56 -0500 From: "Michael S. Tsirkin" To: Khazhismel Kumykov Cc: jasowang@redhat.com, wei.w.wang@intel.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH 1/2] virtio_balloon: fix pages_to_free calculation Message-ID: <20191118175114-mutt-send-email-mst@kernel.org> References: <20191118213811.22017-1-khazhy@google.com> MIME-Version: 1.0 In-Reply-To: <20191118213811.22017-1-khazhy@google.com> X-MC-Unique: -9ChDMr9PF27kXAqmClMKA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 18, 2019 at 01:38:10PM -0800, Khazhismel Kumykov wrote: > freed_pages was accumulating total freed pages, but was also subtracted > on each iteration from pages_to_free, which could potentially result in > attempting to free fewer pages than asked for. This change also makes > both freed_pages and pages_to_free in terms of "balloon pages", where > they were mismatched before. And then patch 2/2 changes it back to both be regular pages. Which is good, but why do we have to go back and forth breaking then fixing it back? >=20 > Fixes: 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"= ) > Cc: Wei Wang > Signed-off-by: Khazhismel Kumykov > --- > drivers/virtio/virtio_balloon.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) >=20 > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_ball= oon.c > index 226fbb995fb0..7cf9540a40b8 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -782,11 +782,8 @@ static unsigned long shrink_balloon_pages(struct vir= tio_balloon *vb, > =09 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it > =09 * multiple times to deflate pages till reaching pages_to_free. > =09 */ > -=09while (vb->num_pages && pages_to_free) { > -=09=09pages_freed +=3D leak_balloon(vb, pages_to_free) / > -=09=09=09=09=09VIRTIO_BALLOON_PAGES_PER_PAGE; > -=09=09pages_to_free -=3D pages_freed; > -=09} > +=09while (vb->num_pages && pages_to_free > pages_freed) > +=09=09pages_freed +=3D leak_balloon(vb, pages_to_free - pages_freed); > =09update_balloon_size(vb); > =20 > =09return pages_freed; > --=20 > 2.24.0.432.g9d3f5f5b63-goog