Re: [Qemu-devel] [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process
>
>
> > +static void free_extended_page_bitmap(struct virtio_balloon *vb) {
> > + int i, bmap_count = vb->nr_page_bmap;
> > +
> > + for (i = 1; i < bmap_count; i++) {
> > + kfree(vb->page_bitmap[i]);
> > + vb->page_bitmap[i] = NULL;
> > + vb->nr_page_bmap--;
> > + }
> > +}
> > +
> > +static void kfree_page_bitmap(struct virtio_balloon *vb) {
> > + int i;
> > +
> > + for (i = 0; i < vb->nr_page_bmap; i++)
> > + kfree(vb->page_bitmap[i]);
> > +}
>
> It might be worth commenting that pair of functions to make it clear why
> they are so different; I guess the kfree_page_bitmap is used just before you
> free the structure above it so you don't need to keep the count/pointers
> updated?
>
Yes. I will add some comments for that. Thanks!
Liang
> Dave
> --
> Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
Re: [Qemu-devel] [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process
On Thu, Jan 19, 2017 at 01:44:36AM +, Li, Liang Z wrote:
> > > > > + *range = cpu_to_le64((base_pfn <<
> > > > > + VIRTIO_BALLOON_NR_PFN_BITS) | 0);
> > > > > + *(range + 1) = cpu_to_le64(pages);
> > > > > + vb->resp_pos += 2;
> > > >
> > > > Pls use structs for this kind of stuff.
> > >
> > > I am not sure if you mean to use
> > >
> > > struct range {
> > > __le64 pfn: 52;
> > > __le64 nr_page: 12
> > > }
> > > Instead of the shift operation?
> >
> > Not just that. You want to add a pages field as well.
> >
>
> pages field? Could you give more hints?
Well look how you are formatting it manually above.
There is clearly a structure with two 64 bit fields.
First one includes pfn and 0 (no idea why does | 0 make
sense but that's a separate issue).
Second one includes the pages value.
> > Generally describe the format in the header in some way so host and guest
> > can easily stay in sync.
>
> 'VIRTIO_BALLOON_NR_PFN_BITS' is for this purpose and it will be passed to the
> related function in page_alloc.c as a parameter.
>
> Thanks!
> Liang
> > All the pointer math and void * means we get zero type safety and I'm not
> > happy about it.
> >
> > It's not good that virtio format seeps out to page_alloc anyway.
> > If unavoidable it is not a good idea to try to hide this fact, people will
> > assume
> > they can change the format at will.
> >
> > --
> > MST
Re: [Qemu-devel] [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process
* Liang Li (liang.z...@intel.com) wrote:
> +static void free_extended_page_bitmap(struct virtio_balloon *vb)
> +{
> + int i, bmap_count = vb->nr_page_bmap;
> +
> + for (i = 1; i < bmap_count; i++) {
> + kfree(vb->page_bitmap[i]);
> + vb->page_bitmap[i] = NULL;
> + vb->nr_page_bmap--;
> + }
> +}
> +
> +static void kfree_page_bitmap(struct virtio_balloon *vb)
> +{
> + int i;
> +
> + for (i = 0; i < vb->nr_page_bmap; i++)
> + kfree(vb->page_bitmap[i]);
> +}
It might be worth commenting that pair of functions to make it clear
why they are so different; I guess the kfree_page_bitmap
is used just before you free the structure above it so you
don't need to keep the count/pointers updated?
Dave
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
Re: [Qemu-devel] [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process
> On Wed, Jan 18, 2017 at 04:56:58AM +, Li, Liang Z wrote:
> > > > - virtqueue_add_outbuf(vq, , 1, vb, GFP_KERNEL);
> > > > - virtqueue_kick(vq);
> > > > +static void do_set_resp_bitmap(struct virtio_balloon *vb,
> > > > + unsigned long base_pfn, int pages)
> > > >
> > > > - /* When host has read buffer, this completes via balloon_ack */
> > > > - wait_event(vb->acked, virtqueue_get_buf(vq, ));
> > > > +{
> > > > + __le64 *range = vb->resp_data + vb->resp_pos;
> > > >
> > > > + if (pages > (1 << VIRTIO_BALLOON_NR_PFN_BITS)) {
> > > > + /* when the length field can't contain pages, set it to
> > > > 0 to
> > >
> > > /*
> > > * Multi-line
> > > * comments
> > > * should look like this.
> > > */
> > >
> > > Also, pls start sentences with an upper-case letter.
> > >
> >
> > Sorry for that.
> >
> > > > +* indicate the actual length is in the next __le64;
> > > > +*/
> > >
> > > This is part of the interface so should be documented as such.
> > >
> > > > + *range = cpu_to_le64((base_pfn <<
> > > > + VIRTIO_BALLOON_NR_PFN_BITS) | 0);
> > > > + *(range + 1) = cpu_to_le64(pages);
> > > > + vb->resp_pos += 2;
> > >
> > > Pls use structs for this kind of stuff.
> >
> > I am not sure if you mean to use
> >
> > struct range {
> > __le64 pfn: 52;
> > __le64 nr_page: 12
> > }
> > Instead of the shift operation?
>
> Not just that. You want to add a pages field as well.
>
pages field? Could you give more hints?
> Generally describe the format in the header in some way so host and guest
> can easily stay in sync.
'VIRTIO_BALLOON_NR_PFN_BITS' is for this purpose and it will be passed to the
related function in page_alloc.c as a parameter.
Thanks!
Liang
> All the pointer math and void * means we get zero type safety and I'm not
> happy about it.
>
> It's not good that virtio format seeps out to page_alloc anyway.
> If unavoidable it is not a good idea to try to hide this fact, people will
> assume
> they can change the format at will.
>
> --
> MST
Re: [Qemu-devel] [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process
On Wed, Jan 18, 2017 at 04:56:58AM +, Li, Liang Z wrote:
> > > - virtqueue_add_outbuf(vq, , 1, vb, GFP_KERNEL);
> > > - virtqueue_kick(vq);
> > > +static void do_set_resp_bitmap(struct virtio_balloon *vb,
> > > + unsigned long base_pfn, int pages)
> > >
> > > - /* When host has read buffer, this completes via balloon_ack */
> > > - wait_event(vb->acked, virtqueue_get_buf(vq, ));
> > > +{
> > > + __le64 *range = vb->resp_data + vb->resp_pos;
> > >
> > > + if (pages > (1 << VIRTIO_BALLOON_NR_PFN_BITS)) {
> > > + /* when the length field can't contain pages, set it to 0 to
> >
> > /*
> > * Multi-line
> > * comments
> > * should look like this.
> > */
> >
> > Also, pls start sentences with an upper-case letter.
> >
>
> Sorry for that.
>
> > > + * indicate the actual length is in the next __le64;
> > > + */
> >
> > This is part of the interface so should be documented as such.
> >
> > > + *range = cpu_to_le64((base_pfn <<
> > > + VIRTIO_BALLOON_NR_PFN_BITS) | 0);
> > > + *(range + 1) = cpu_to_le64(pages);
> > > + vb->resp_pos += 2;
> >
> > Pls use structs for this kind of stuff.
>
> I am not sure if you mean to use
>
> struct range {
> __le64 pfn: 52;
> __le64 nr_page: 12
> }
> Instead of the shift operation?
Not just that. You want to add a pages field as well.
Generally describe the format in the header in some way
so host and guest can easily stay in sync.
All the pointer math and void * means we get zero type
safety and I'm not happy about it.
> I didn't use this way because I don't want to include 'virtio-balloon.h' in
> page_alloc.c,
> or copy the define of this struct in page_alloc.c
>
> Thanks!
> Liang
It's not good that virtio format seeps out to page_alloc anyway.
If unavoidable it is not a good idea to try to hide this fact,
people will assume they can change the format at will.
--
MST
Re: [Qemu-devel] [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process
> > - virtqueue_add_outbuf(vq, , 1, vb, GFP_KERNEL);
> > - virtqueue_kick(vq);
> > +static void do_set_resp_bitmap(struct virtio_balloon *vb,
> > + unsigned long base_pfn, int pages)
> >
> > - /* When host has read buffer, this completes via balloon_ack */
> > - wait_event(vb->acked, virtqueue_get_buf(vq, ));
> > +{
> > + __le64 *range = vb->resp_data + vb->resp_pos;
> >
> > + if (pages > (1 << VIRTIO_BALLOON_NR_PFN_BITS)) {
> > + /* when the length field can't contain pages, set it to 0 to
>
> /*
> * Multi-line
> * comments
> * should look like this.
> */
>
> Also, pls start sentences with an upper-case letter.
>
Sorry for that.
> > +* indicate the actual length is in the next __le64;
> > +*/
>
> This is part of the interface so should be documented as such.
>
> > + *range = cpu_to_le64((base_pfn <<
> > + VIRTIO_BALLOON_NR_PFN_BITS) | 0);
> > + *(range + 1) = cpu_to_le64(pages);
> > + vb->resp_pos += 2;
>
> Pls use structs for this kind of stuff.
I am not sure if you mean to use
struct range {
__le64 pfn: 52;
__le64 nr_page: 12
}
Instead of the shift operation?
I didn't use this way because I don't want to include 'virtio-balloon.h' in
page_alloc.c,
or copy the define of this struct in page_alloc.c
Thanks!
Liang
Re: [Qemu-devel] [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process
On Wed, Dec 21, 2016 at 02:52:26PM +0800, Liang Li wrote:
>
> - /* We should always be able to add one buffer to an empty queue. */
> - virtqueue_add_outbuf(vq, , 1, vb, GFP_KERNEL);
> - virtqueue_kick(vq);
> +static void do_set_resp_bitmap(struct virtio_balloon *vb,
> + unsigned long base_pfn, int pages)
>
> - /* When host has read buffer, this completes via balloon_ack */
> - wait_event(vb->acked, virtqueue_get_buf(vq, ));
> +{
> + __le64 *range = vb->resp_data + vb->resp_pos;
>
> + if (pages > (1 << VIRTIO_BALLOON_NR_PFN_BITS)) {
> + /* when the length field can't contain pages, set it to 0 to
/*
* Multi-line
* comments
* should look like this.
*/
Also, pls start sentences with an upper-case letter.
> + * indicate the actual length is in the next __le64;
> + */
This is part of the interface so should be documented as such.
> + *range = cpu_to_le64((base_pfn <<
> + VIRTIO_BALLOON_NR_PFN_BITS) | 0);
> + *(range + 1) = cpu_to_le64(pages);
> + vb->resp_pos += 2;
Pls use structs for this kind of stuff.
> + } else {
> + *range = (base_pfn << VIRTIO_BALLOON_NR_PFN_BITS) | pages;
> + vb->resp_pos++;
> + }
> +}
[Qemu-devel] [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process
The implementation of the current virtio-balloon is not very
efficient, the time spends on different stages of inflating
the balloon to 7GB of a 8GB idle guest:
a. allocating pages (6.5%)
b. sending PFNs to host (68.3%)
c. address translation (6.1%)
d. madvise (19%)
It takes about 4126ms for the inflating process to complete.
Debugging shows that the bottle neck are the stage b and stage d.
If using {pfn|length} array to send the page info instead of the
PFNs, we can reduce the overhead in stage b quite a lot.
Furthermore, we can do the address translation and call madvise()
with a range of memory, instead of the current page per page way,
the overhead of stage c and stage d can also be reduced a lot.
This patch is the kernel side implementation which is intended to
speed up the inflating & deflating process by adding a new feature
to the virtio-balloon device. With this new feature, inflating the
balloon to 7GB of a 8GB idle guest only takes 590ms, the
performance improvement is about 85%.
TODO: optimize stage a by allocating/freeing a chunk of pages
instead of a single page at a time.
Signed-off-by: Liang Li
Suggested-by: Michael S. Tsirkin
Cc: Michael S. Tsirkin
Cc: Paolo Bonzini
Cc: Cornelia Huck
Cc: Amit Shah
Cc: Dave Hansen
Cc: Andrea Arcangeli
Cc: David Hildenbrand
---
drivers/virtio/virtio_balloon.c | 348
1 file changed, 320 insertions(+), 28 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index f59cb4f..03383b3 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -42,6 +42,10 @@
#define OOM_VBALLOON_DEFAULT_PAGES 256
#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
+#define BALLOON_BMAP_SIZE (8 * PAGE_SIZE)
+#define PFNS_PER_BMAP (BALLOON_BMAP_SIZE * BITS_PER_BYTE)
+#define BALLOON_BMAP_COUNT 32
+
static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
module_param(oom_pages, int, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
@@ -67,6 +71,20 @@ struct virtio_balloon {
/* Number of balloon pages we've told the Host we're not using. */
unsigned int num_pages;
+ /* Pointer to the response header. */
+ void *resp_hdr;
+ /* Pointer to the start address of response data. */
+ __le64 *resp_data;
+ /* Size of response data buffer. */
+ unsigned int resp_buf_size;
+ /* Pointer offset of the response data. */
+ unsigned int resp_pos;
+ /* Bitmap used to save the pfns info */
+ unsigned long *page_bitmap[BALLOON_BMAP_COUNT];
+ /* Number of split page bitmaps */
+ unsigned int nr_page_bmap;
+ /* Used to record the processed pfn range */
+ unsigned long min_pfn, max_pfn, start_pfn, end_pfn;
/*
* The pages we've told the Host we're not using are enqueued
* at vb_dev_info->pages list.
@@ -110,20 +128,180 @@ static void balloon_ack(struct virtqueue *vq)
wake_up(>acked);
}
-static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
+static inline void init_bmap_pfn_range(struct virtio_balloon *vb)
{
- struct scatterlist sg;
+ vb->min_pfn = ULONG_MAX;
+ vb->max_pfn = 0;
+}
+
+static inline void update_bmap_pfn_range(struct virtio_balloon *vb,
+struct page *page)
+{
+ unsigned long balloon_pfn = page_to_balloon_pfn(page);
+
+ vb->min_pfn = min(balloon_pfn, vb->min_pfn);
+ vb->max_pfn = max(balloon_pfn, vb->max_pfn);
+}
+
+static void extend_page_bitmap(struct virtio_balloon *vb,
+ unsigned long nr_pfn)
+{
+ int i, bmap_count;
+ unsigned long bmap_len;
+
+ bmap_len = ALIGN(nr_pfn, BITS_PER_LONG) / BITS_PER_BYTE;
+ bmap_len = ALIGN(bmap_len, BALLOON_BMAP_SIZE);
+ bmap_count = min((int)(bmap_len / BALLOON_BMAP_SIZE),
+BALLOON_BMAP_COUNT);
+
+ for (i = 1; i < bmap_count; i++) {
+ vb->page_bitmap[i] = kmalloc(BALLOON_BMAP_SIZE, GFP_KERNEL);
+ if (vb->page_bitmap[i])
+ vb->nr_page_bmap++;
+ else
+ break;
+ }
+}
+
+static void free_extended_page_bitmap(struct virtio_balloon *vb)
+{
+ int i, bmap_count = vb->nr_page_bmap;
+
+ for (i = 1; i < bmap_count; i++) {
+ kfree(vb->page_bitmap[i]);
+ vb->page_bitmap[i] = NULL;
+ vb->nr_page_bmap--;
+ }
+}
+
+static void kfree_page_bitmap(struct virtio_balloon *vb)
+{
+ int i;
+
+ for (i = 0; i < vb->nr_page_bmap; i++)
+ kfree(vb->page_bitmap[i]);
+}
+
+static void clear_page_bitmap(struct virtio_balloon *vb)
+{
+ int i;
+
+ for
