From: "Michael S. Tsirkin" <mst@redhat.com>
To: Khazhismel Kumykov <khazhy@google.com>
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
Date: Mon, 18 Nov 2019 17:52:56 -0500 [thread overview]
Message-ID: <20191118175114-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20191118213811.22017-1-khazhy@google.com>
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?
>
> Fixes: 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker")
> Cc: Wei Wang <wei.w.wang@intel.com>
> Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
> ---
> drivers/virtio/virtio_balloon.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.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 virtio_balloon *vb,
> * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
> * multiple times to deflate pages till reaching pages_to_free.
> */
> - while (vb->num_pages && pages_to_free) {
> - pages_freed += leak_balloon(vb, pages_to_free) /
> - VIRTIO_BALLOON_PAGES_PER_PAGE;
> - pages_to_free -= pages_freed;
> - }
> + while (vb->num_pages && pages_to_free > pages_freed)
> + pages_freed += leak_balloon(vb, pages_to_free - pages_freed);
> update_balloon_size(vb);
>
> return pages_freed;
> --
> 2.24.0.432.g9d3f5f5b63-goog
next prev parent reply other threads:[~2019-11-18 22:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-15 22:55 [PATCH] virtio_balloon: fix shrinker pages_to_free calculation Khazhismel Kumykov
2019-11-18 4:01 ` Wei Wang
2019-11-18 5:30 ` Michael S. Tsirkin
2019-11-18 7:42 ` Wei Wang
2019-11-18 8:26 ` Michael S. Tsirkin
2019-11-18 10:31 ` Wei Wang
2019-11-18 5:26 ` Michael S. Tsirkin
2019-11-18 21:30 ` Khazhismel Kumykov
2019-11-18 21:38 ` [PATCH 1/2] virtio_balloon: fix " Khazhismel Kumykov
2019-11-18 21:38 ` [PATCH 2/2] virtio_balloon: fix shrinker_scan return units Khazhismel Kumykov
2019-11-18 22:56 ` Michael S. Tsirkin
2019-11-18 22:52 ` Michael S. Tsirkin [this message]
2019-11-18 23:08 ` [PATCH 1/2] virtio_balloon: fix pages_to_free calculation Michael S. Tsirkin
2019-11-18 23:20 ` Khazhismel Kumykov
2019-11-19 5:38 ` Wei Wang
2019-11-19 9:37 ` Michael S. Tsirkin
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