From: "Michael S. Tsirkin" <mst@redhat.com>
To: "Li, Liang Z" <liang.z.li@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"virtio-dev@lists.oasis-open.org"
<virtio-dev@lists.oasis-open.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"dgilbert@redhat.com" <dgilbert@redhat.com>,
"quintela@redhat.com" <quintela@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Mel Gorman <mgorman@techsingularity.net>,
Paolo Bonzini <pbonzini@redhat.com>,
Cornelia Huck <cornelia.huck@de.ibm.com>,
Amit Shah <amit.shah@redhat.com>
Subject: Re: [PATCH v2 repost 7/7] virtio-balloon: tell host vm's free page info
Date: Fri, 29 Jul 2016 00:37:24 +0300 [thread overview]
Message-ID: <20160729003622-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <F2CBF3009FA73547804AE4C663CAB28E042141EE@shsmsx102.ccr.corp.intel.com>
On Thu, Jul 28, 2016 at 07:50:52AM +0000, Li, Liang Z wrote:
> > > }
> > >
> > > +static void update_free_pages_stats(struct virtio_balloon *vb,
> >
> > why _stats?
>
> Will change.
>
> > > + max_pfn = get_max_pfn();
> > > + mutex_lock(&vb->balloon_lock);
> > > + while (pfn < max_pfn) {
> > > + memset(vb->page_bitmap, 0, vb->bmap_len);
> > > + ret = get_free_pages(pfn, pfn + vb->pfn_limit,
> > > + vb->page_bitmap, vb->bmap_len * BITS_PER_BYTE);
> > > + hdr->cmd = cpu_to_virtio16(vb->vdev,
> > BALLOON_GET_FREE_PAGES);
> > > + hdr->page_shift = cpu_to_virtio16(vb->vdev, PAGE_SHIFT);
> > > + hdr->req_id = cpu_to_virtio64(vb->vdev, req_id);
> > > + hdr->start_pfn = cpu_to_virtio64(vb->vdev, pfn);
> > > + bmap_len = vb->pfn_limit / BITS_PER_BYTE;
> > > + if (!ret) {
> > > + hdr->flag = cpu_to_virtio16(vb->vdev,
> > > +
> > BALLOON_FLAG_DONE);
> > > + if (pfn + vb->pfn_limit > max_pfn)
> > > + bmap_len = (max_pfn - pfn) /
> > BITS_PER_BYTE;
> > > + } else
> > > + hdr->flag = cpu_to_virtio16(vb->vdev,
> > > +
> > BALLOON_FLAG_CONT);
> > > + hdr->bmap_len = cpu_to_virtio64(vb->vdev, bmap_len);
> > > + sg_init_one(&sg_out, hdr,
> > > + sizeof(struct balloon_bmap_hdr) + bmap_len);
> >
> > Wait a second. This adds the same buffer multiple times in a loop.
> > We will overwrite the buffer without waiting for hypervisor to process it.
> > What did I miss?
>
> I am no quite sure about this part, I though the virtqueue_kick(vq) will prevent
> the buffer from overwrite, I realized it's wrong.
>
> > > +
> > > + virtqueue_add_outbuf(vq, &sg_out, 1, vb, GFP_KERNEL);
> >
> > this can fail. you want to maybe make sure vq has enough space before you
> > use it or check error and wait.
> >
> > > + virtqueue_kick(vq);
> >
> > why kick here within loop? wait until done. in fact kick outside lock is better
> > for smp.
>
> I will change this part in v3.
>
> >
> > > + pfn += vb->pfn_limit;
> > > + static const char * const names[] = { "inflate", "deflate", "stats",
> > > + "misc" };
> > > int err, nvqs;
> > >
> > > /*
> > > * We expect two virtqueues: inflate and deflate, and
> > > * optionally stat.
> > > */
> > > - nvqs = virtio_has_feature(vb->vdev,
> > VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
> > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_MISC_VQ))
> > > + nvqs = 4;
> >
> > Does misc vq depend on stats vq feature then? if yes please validate that.
>
> Yes, what's you mean by 'validate' that?
Either handle misc vq without a stats vq, or
clear VIRTIO_BALLOON_F_MISC_VQ if stats vq is off.
> >
> >
> > > + else
> > > + nvqs = virtio_has_feature(vb->vdev,
> > > + VIRTIO_BALLOON_F_STATS_VQ) ? 3 :
> > 2;
> >
> > Replace that ? with else too pls.
>
> Will change.
>
> Thanks!
> Liang
prev parent reply other threads:[~2016-07-28 21:37 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-27 1:23 [PATCH v2 repost 0/7] Extend virtio-balloon for fast (de)inflating & fast live migration Liang Li
2016-07-27 1:23 ` [PATCH v2 repost 1/7] virtio-balloon: rework deflate to add page to a list Liang Li
2016-07-27 1:23 ` [PATCH v2 repost 2/7] virtio-balloon: define new feature bit and page bitmap head Liang Li
2016-07-27 1:23 ` [PATCH v2 repost 3/7] mm: add a function to get the max pfn Liang Li
2016-07-27 22:08 ` Michael S. Tsirkin
2016-07-27 22:52 ` Dave Hansen
2016-07-27 1:23 ` [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate process Liang Li
2016-07-27 16:03 ` Dave Hansen
2016-07-27 21:39 ` Michael S. Tsirkin
2016-07-28 3:30 ` Li, Liang Z
2016-07-28 22:15 ` Michael S. Tsirkin
2016-07-29 1:08 ` [virtio-dev] " Li, Liang Z
2016-07-28 1:13 ` Li, Liang Z
2016-07-28 1:45 ` Michael S. Tsirkin
2016-07-28 6:36 ` [virtio-dev] " Li, Liang Z
2016-07-28 21:51 ` Michael S. Tsirkin
2016-07-29 0:46 ` Li, Liang Z
2016-07-29 19:48 ` Dave Hansen
2016-08-02 0:28 ` Li, Liang Z
2016-07-27 21:36 ` Michael S. Tsirkin
2016-07-28 3:06 ` Li, Liang Z
2016-07-28 22:17 ` Michael S. Tsirkin
2016-07-29 0:38 ` Li, Liang Z
2016-07-27 22:07 ` Michael S. Tsirkin
2016-07-28 3:48 ` Li, Liang Z
2016-07-27 1:23 ` [PATCH v2 repost 5/7] virtio-balloon: define feature bit and head for misc virt queue Liang Li
2016-07-27 1:23 ` [PATCH v2 repost 6/7] mm: add the related functions to get free page info Liang Li
2016-07-27 16:40 ` Dave Hansen
2016-07-27 22:05 ` Michael S. Tsirkin
2016-07-27 22:16 ` Dave Hansen
2016-07-27 23:05 ` Michael S. Tsirkin
2016-07-28 4:36 ` Li, Liang Z
2016-07-28 0:10 ` Li, Liang Z
2016-07-28 0:17 ` Michael S. Tsirkin
2016-07-27 22:13 ` Michael S. Tsirkin
2016-07-28 5:30 ` [virtio-dev] " Li, Liang Z
2016-07-27 1:23 ` [PATCH v2 repost 7/7] virtio-balloon: tell host vm's " Liang Li
2016-07-27 22:00 ` Michael S. Tsirkin
2016-07-28 7:50 ` Li, Liang Z
2016-07-28 21:37 ` Michael S. Tsirkin [this message]
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