Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1742498 > unrolled thread

[PATCH v16 0/5] Virtio-balloon Enhancement

Back to article view | Back to linux.kernel

Contents

  [PATCH v16 0/5] Virtio-balloon Enhancement Wei Wang <wei.w.wang@intel.com> - 2017-09-30 06:20 +0200
    [PATCH v16 4/5] mm: support reporting free page blocks Wei Wang <wei.w.wang@intel.com> - 2017-09-30 06:20 +0200
    [PATCH v16 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG Wei Wang <wei.w.wang@intel.com> - 2017-09-30 06:30 +0200
      Re: [PATCH v16 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG "Michael S. Tsirkin" <mst@redhat.com> - 2017-10-02 06:40 +0200
        RE: [PATCH v16 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG "Wang, Wei W" <wei.w.wang@intel.com> - 2017-10-02 14:40 +0200
    Re: [PATCH v16 0/5] Virtio-balloon Enhancement Damian Tometzki <damian.tometzki@icloud.com> - 2017-10-01 15:30 +0200
    Re: [PATCH v16 0/5] Virtio-balloon Enhancement Damian Tometzki <damian.tometzki@icloud.com> - 2017-10-01 16:20 +0200

#1742498 — [PATCH v16 0/5] Virtio-balloon Enhancement

This patch series enhances the existing virtio-balloon with the following
new features:
1) fast ballooning: transfer ballooned pages between the guest and host in
chunks using sgs, instead of one array each time; and
2) free page block reporting: a new virtqueue to report guest free pages
to the host.

The second feature can be used to accelerate live migration of VMs. Here
are some details:

Live migration needs to transfer the VM's memory from the source machine
to the destination round by round. For the 1st round, all the VM's memory
is transferred. From the 2nd round, only the pieces of memory that were
written by the guest (after the 1st round) are transferred. One method
that is popularly used by the hypervisor to track which part of memory is
written is to write-protect all the guest memory.

The second feature enables the optimization of the 1st round memory
transfer - the hypervisor can skip the transfer of guest free pages in the
1st round. It is not concerned that the memory pages are used after they
are given to the hypervisor as a hint of the free pages, because they will
be tracked by the hypervisor and transferred in the next round if they are
used and written.

Change Log:
v15->v16:
1) mm: stop reporting the free pfn range if the callback returns false;
2) mm: move some implementaion of walk_free_mem_block into a function to
make the code layout looks better;
3) xbitmap: added some optimizations suggested by Matthew, please refer to
the ChangLog in the xbitmap patch for details.
4) xbitmap: added a test suite
5) virtio-balloon: bail out with a warning when virtqueue_add_inbuf returns
an error
6) virtio-balloon: some small code re-arrangement, e.g. detachinf used buf
from the vq before adding a new buf

v14->v15:
1) mm: make the report callback return a bool value - returning 1 to stop
walking through the free page list.
2) virtio-balloon: batching sgs of balloon pages till the vq is full
3) virtio-balloon: create a new workqueue, rather than using the default
system_wq, to queue the free page reporting work item.
4) virtio-balloon: add a ctrl_vq to be a central control plane which will
handle all the future control related commands between the host and guest.
Add free page report as the first feature controlled under ctrl_vq, and
the free_page_vq is a data plane vq dedicated to the transmission of free
page blocks.

v13->v14:
1) xbitmap: move the code from lib/radix-tree.c to lib/xbitmap.c.
2) xbitmap: consolidate the implementation of xb_bit_set/clear/test into
one xb_bit_ops.
3) xbitmap: add documents for the exported APIs.
4) mm: rewrite the function to walk through free page blocks.
5) virtio-balloon: when reporting a free page blcok to the device, if the
vq is full (less likey to happen in practice), just skip reporting this
block, instead of busywaiting till an entry gets released.
6) virtio-balloon: fail the probe function if adding the signal buf in
init_vqs fails.

v12->v13:
1) mm: use a callback function to handle the the free page blocks from the
report function. This avoids exposing the zone internal to a kernel
module.
2) virtio-balloon: send balloon pages or a free page block using a single
sg each time. This has the benefits of simpler implementation with no new
APIs.
3) virtio-balloon: the free_page_vq is used to report free pages only (no
multiple usages interleaving)
4) virtio-balloon: Balloon pages and free page blocks are sent via input
sgs, and the completion signal to the host is sent via an output sg.

v11->v12:
1) xbitmap: use the xbitmap from Matthew Wilcox to record ballooned pages.
2) virtio-ring: enable the driver to build up a desc chain using vring
desc.
3) virtio-ring: Add locking to the existing START_USE() and END_USE()
macro to lock/unlock the vq when a vq operation starts/ends.
4) virtio-ring: add virtqueue_kick_sync() and virtqueue_kick_async()
5) virtio-balloon: describe chunks of ballooned pages and free pages
blocks directly using one or more chains of desc from the vq.

v10->v11:
1) virtio_balloon: use vring_desc to describe a chunk;
2) virtio_ring: support to add an indirect desc table to virtqueue;
3)  virtio_balloon: use cmdq to report guest memory statistics.

v9->v10:
1) mm: put report_unused_page_block() under CONFIG_VIRTIO_BALLOON;
2) virtio-balloon: add virtballoon_validate();
3) virtio-balloon: msg format change;
4) virtio-balloon: move miscq handling to a task on system_freezable_wq;
5) virtio-balloon: code cleanup.

v8->v9:
1) Split the two new features, VIRTIO_BALLOON_F_BALLOON_CHUNKS and
VIRTIO_BALLOON_F_MISC_VQ, which were mixed together in the previous
implementation;
2) Simpler function to get the free page block.

v7->v8:
1) Use only one chunk format, instead of two.
2) re-write the virtio-balloon implementation patch.
3) commit changes
4) patch re-org

Matthew Wilcox (2):
  lib/xbitmap: Introduce xbitmap
  radix tree test suite: add tests for xbitmap

Wei Wang (3):
  virtio-balloon: VIRTIO_BALLOON_F_SG
  mm: support reporting free page blocks
  virtio-balloon: VIRTIO_BALLOON_F_CTRL_VQ

 drivers/virtio/virtio_balloon.c         | 437 +++++++++++++++++++++++++++++---
 include/linux/mm.h                      |   6 +
 include/linux/radix-tree.h              |   2 +
 include/linux/xbitmap.h                 |  66 +++++
 include/uapi/linux/virtio_balloon.h     |  16 ++
 lib/Makefile                            |   2 +-
 lib/radix-tree.c                        |  42 ++-
 lib/xbitmap.c                           | 264 +++++++++++++++++++
 mm/page_alloc.c                         |  91 +++++++
 tools/include/linux/bitmap.h            |  34 +++
 tools/include/linux/kernel.h            |   2 +
 tools/testing/radix-tree/Makefile       |   7 +-
 tools/testing/radix-tree/linux/kernel.h |   2 -
 tools/testing/radix-tree/main.c         |   5 +
 tools/testing/radix-tree/test.h         |   1 +
 tools/testing/radix-tree/xbitmap.c      | 269 ++++++++++++++++++++
 16 files changed, 1203 insertions(+), 43 deletions(-)
 create mode 100644 include/linux/xbitmap.h
 create mode 100644 lib/xbitmap.c
 create mode 100644 tools/testing/radix-tree/xbitmap.c

-- 
2.7.4

[toc] | [next] | [standalone]

#1742499 — [PATCH v16 4/5] mm: support reporting free page blocks

This patch adds support to walk through the free page blocks in the
system and report them via a callback function. Some page blocks may
leave the free list after zone->lock is released, so it is the caller's
responsibility to either detect or prevent the use of such pages.

One use example of this patch is to accelerate live migration by skipping
the transfer of free pages reported from the guest. A popular method used
by the hypervisor to track which part of memory is written during live
migration is to write-protect all the guest memory. So, those pages that
are reported as free pages but are written after the report function
returns will be captured by the hypervisor, and they will be added to the
next round of memory transfer.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Liang Li <liang.z.li@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
---
 include/linux/mm.h |  6 ++++
 mm/page_alloc.c    | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 97 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 46b9ac5..d9652c2 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1835,6 +1835,12 @@ extern void free_area_init_node(int nid, unsigned long * zones_size,
 		unsigned long zone_start_pfn, unsigned long *zholes_size);
 extern void free_initmem(void);
 
+extern void walk_free_mem_block(void *opaque,
+				int min_order,
+				bool (*report_pfn_range)(void *opaque,
+							 unsigned long pfn,
+							 unsigned long num));
+
 /*
  * Free reserved pages within range [PAGE_ALIGN(start), end & PAGE_MASK)
  * into the buddy system. The freed pages will be poisoned with pattern
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6d00f74..c6bb874 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4762,6 +4762,97 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
 	show_swap_cache_info();
 }
 
+/*
+ * Walk through a free page list and report the found pfn range via the
+ * callback.
+ *
+ * Return false if the callback requests to stop reporting. Otherwise,
+ * return true.
+ */
+static bool walk_free_page_list(void *opaque,
+				struct zone *zone,
+				int order,
+				enum migratetype mt,
+				bool (*report_pfn_range)(void *,
+							 unsigned long,
+							 unsigned long))
+{
+	struct page *page;
+	struct list_head *list;
+	unsigned long pfn, flags;
+	bool ret;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	list = &zone->free_area[order].free_list[mt];
+	list_for_each_entry(page, list, lru) {
+		pfn = page_to_pfn(page);
+		ret = report_pfn_range(opaque, pfn, 1 << order);
+		if (!ret)
+			break;
+	}
+	spin_unlock_irqrestore(&zone->lock, flags);
+
+	return ret;
+}
+
+/**
+ * walk_free_mem_block - Walk through the free page blocks in the system
+ * @opaque: the context passed from the caller
+ * @min_order: the minimum order of free lists to check
+ * @report_pfn_range: the callback to report the pfn range of the free pages
+ *
+ * If the callback returns false, stop iterating the list of free page blocks.
+ * Otherwise, continue to report.
+ *
+ * Please note that there are no locking guarantees for the callback and
+ * that the reported pfn range might be freed or disappear after the
+ * callback returns so the caller has to be very careful how it is used.
+ *
+ * The callback itself must not sleep or perform any operations which would
+ * require any memory allocations directly (not even GFP_NOWAIT/GFP_ATOMIC)
+ * or via any lock dependency. It is generally advisable to implement
+ * the callback as simple as possible and defer any heavy lifting to a
+ * different context.
+ *
+ * There is no guarantee that each free range will be reported only once
+ * during one walk_free_mem_block invocation.
+ *
+ * pfn_to_page on the given range is strongly discouraged and if there is
+ * an absolute need for that make sure to contact MM people to discuss
+ * potential problems.
+ *
+ * The function itself might sleep so it cannot be called from atomic
+ * contexts.
+ *
+ * In general low orders tend to be very volatile and so it makes more
+ * sense to query larger ones first for various optimizations which like
+ * ballooning etc... This will reduce the overhead as well.
+ */
+void walk_free_mem_block(void *opaque,
+			 int min_order,
+			 bool (*report_pfn_range)(void *opaque,
+						  unsigned long pfn,
+						  unsigned long num))
+{
+	struct zone *zone;
+	int order;
+	enum migratetype mt;
+	bool ret;
+
+	for_each_populated_zone(zone) {
+		for (order = MAX_ORDER - 1; order >= min_order; order--) {
+			for (mt = 0; mt < MIGRATE_TYPES; mt++) {
+				ret = walk_free_page_list(opaque, zone,
+							  order, mt,
+							  report_pfn_range);
+				if (!ret)
+					return;
+			}
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(walk_free_mem_block);
+
 static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
 {
 	zoneref->zone = zone;
-- 
2.7.4

[toc] | [prev] | [next] | [standalone]

#1742501 — [PATCH v16 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG

Add a new feature, VIRTIO_BALLOON_F_SG, which enables the transfer
of balloon (i.e. inflated/deflated) pages using scatter-gather lists
to the host.

The implementation of the previous virtio-balloon is not very
efficient, because the balloon pages are transferred to the
host one by one. Here is the breakdown of the time in percentage
spent on each step of the balloon inflating process (inflating
7GB of an 8GB idle guest).

1) allocating pages (6.5%)
2) sending PFNs to host (68.3%)
3) address translation (6.1%)
4) madvise (19%)

It takes about 4126ms for the inflating process to complete.
The above profiling shows that the bottlenecks are stage 2)
and stage 4).

This patch optimizes step 2) by transferring pages to the host in
sgs. An sg describes a chunk of guest physically continuous pages.
With this mechanism, step 4) can also be optimized by doing address
translation and madvise() in chunks rather than page by page.

With this new feature, the above ballooning process takes ~492ms
resulting in an improvement of ~88%.

TODO: optimize stage 1) by allocating/freeing a chunk of pages
instead of a single page each time.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Liang Li <liang.z.li@intel.com>
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/virtio/virtio_balloon.c     | 188 ++++++++++++++++++++++++++++++++----
 include/uapi/linux/virtio_balloon.h |   1 +
 2 files changed, 172 insertions(+), 17 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index f0b3a0b..6952e19 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -32,6 +32,8 @@
 #include <linux/mm.h>
 #include <linux/mount.h>
 #include <linux/magic.h>
+#include <linux/xbitmap.h>
+#include <asm/page.h>
 
 /*
  * Balloon device works in 4K page units.  So each page is pointed to by
@@ -79,6 +81,9 @@ struct virtio_balloon {
 	/* Synchronize access/update to this struct virtio_balloon elements */
 	struct mutex balloon_lock;
 
+	/* The xbitmap used to record balloon pages */
+	struct xb page_xb;
+
 	/* The array of pfns we tell the Host about. */
 	unsigned int num_pfns;
 	__virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
@@ -141,13 +146,128 @@ static void set_page_pfns(struct virtio_balloon *vb,
 					  page_to_balloon_pfn(page) + i);
 }
 
+
+static void kick_and_wait(struct virtqueue *vq, wait_queue_head_t wq_head)
+{
+	unsigned int len;
+
+	virtqueue_kick(vq);
+	wait_event(wq_head, virtqueue_get_buf(vq, &len));
+}
+
+static int add_one_sg(struct virtqueue *vq, void *addr, uint32_t size)
+{
+	struct scatterlist sg;
+	unsigned int len;
+
+	sg_init_one(&sg, addr, size);
+
+	/* Detach all the used buffers from the vq */
+	while (virtqueue_get_buf(vq, &len))
+		;
+
+	return virtqueue_add_inbuf(vq, &sg, 1, vq, GFP_KERNEL);
+}
+
+static int send_balloon_page_sg(struct virtio_balloon *vb,
+				 struct virtqueue *vq,
+				 void *addr,
+				 uint32_t size,
+				 bool batch)
+{
+	int err;
+
+	err = add_one_sg(vq, addr, size);
+
+	/* If batchng is requested, we batch till the vq is full */
+	if (!batch || !vq->num_free)
+		kick_and_wait(vq, vb->acked);
+
+	return err;
+}
+
+/*
+ * Send balloon pages in sgs to host. The balloon pages are recorded in the
+ * page xbitmap. Each bit in the bitmap corresponds to a page of PAGE_SIZE.
+ * The page xbitmap is searched for continuous "1" bits, which correspond
+ * to continuous pages, to chunk into sgs.
+ *
+ * @page_xb_start and @page_xb_end form the range of bits in the xbitmap that
+ * need to be searched.
+ */
+static void tell_host_sgs(struct virtio_balloon *vb,
+			  struct virtqueue *vq,
+			  unsigned long page_xb_start,
+			  unsigned long page_xb_end)
+{
+	unsigned long sg_pfn_start, sg_pfn_end;
+	void *sg_addr;
+	uint32_t sg_len, sg_max_len = round_down(UINT_MAX, PAGE_SIZE);
+	int err = 0;
+
+	sg_pfn_start = page_xb_start;
+	while (sg_pfn_start < page_xb_end) {
+		sg_pfn_start = xb_find_next_set_bit(&vb->page_xb, sg_pfn_start,
+						    page_xb_end);
+		if (sg_pfn_start == page_xb_end + 1)
+			break;
+		sg_pfn_end = xb_find_next_zero_bit(&vb->page_xb,
+						   sg_pfn_start + 1,
+						   page_xb_end);
+		sg_addr = (void *)pfn_to_kaddr(sg_pfn_start);
+		sg_len = (sg_pfn_end - sg_pfn_start) << PAGE_SHIFT;
+		while (sg_len > sg_max_len) {
+			err = send_balloon_page_sg(vb, vq, sg_addr, sg_max_len,
+						   true);
+			if (unlikely(err < 0))
+				goto err_out;
+			sg_addr += sg_max_len;
+			sg_len -= sg_max_len;
+		}
+		err = send_balloon_page_sg(vb, vq, sg_addr, sg_len, true);
+		if (unlikely(err < 0))
+			goto err_out;
+		sg_pfn_start = sg_pfn_end + 1;
+	}
+
+	/*
+	 * The last few sgs may not reach the batch size, but need a kick to
+	 * notify the device to handle them.
+	 */
+	if (vq->num_free != virtqueue_get_vring_size(vq))
+		kick_and_wait(vq, vb->acked);
+
+	xb_clear_bit_range(&vb->page_xb, page_xb_start, page_xb_end);
+	return;
+
+err_out:
+	dev_warn(&vb->vdev->dev, "%s failure: %d\n", __func__, err);
+}
+
+static inline void xb_set_page(struct virtio_balloon *vb,
+			       struct page *page,
+			       unsigned long *pfn_min,
+			       unsigned long *pfn_max)
+{
+	unsigned long pfn = page_to_pfn(page);
+
+	*pfn_min = min(pfn, *pfn_min);
+	*pfn_max = max(pfn, *pfn_max);
+	xb_preload(GFP_KERNEL);
+	xb_set_bit(&vb->page_xb, pfn);
+	xb_preload_end();
+}
+
 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 {
 	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 	unsigned num_allocated_pages;
+	bool use_sg = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_SG);
+	unsigned long pfn_max = 0, pfn_min = ULONG_MAX;
 
 	/* We can only do one array worth at a time. */
-	num = min(num, ARRAY_SIZE(vb->pfns));
+	if (!use_sg)
+		num = min(num, ARRAY_SIZE(vb->pfns));
 
 	mutex_lock(&vb->balloon_lock);
 	for (vb->num_pfns = 0; vb->num_pfns < num;
@@ -162,7 +282,12 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 			msleep(200);
 			break;
 		}
-		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
+
+		if (use_sg)
+			xb_set_page(vb, page, &pfn_min, &pfn_max);
+		else
+			set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
+
 		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 		if (!virtio_has_feature(vb->vdev,
 					VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
@@ -171,8 +296,12 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 
 	num_allocated_pages = vb->num_pfns;
 	/* Did we get any? */
-	if (vb->num_pfns != 0)
-		tell_host(vb, vb->inflate_vq);
+	if (vb->num_pfns) {
+		if (use_sg)
+			tell_host_sgs(vb, vb->inflate_vq, pfn_min, pfn_max);
+		else
+			tell_host(vb, vb->inflate_vq);
+	}
 	mutex_unlock(&vb->balloon_lock);
 
 	return num_allocated_pages;
@@ -198,9 +327,12 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 	struct page *page;
 	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 	LIST_HEAD(pages);
+	bool use_sg = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_SG);
+	unsigned long pfn_max = 0, pfn_min = ULONG_MAX;
 
-	/* We can only do one array worth at a time. */
-	num = min(num, ARRAY_SIZE(vb->pfns));
+	/* Traditionally, we can only do one array worth at a time. */
+	if (!use_sg)
+		num = min(num, ARRAY_SIZE(vb->pfns));
 
 	mutex_lock(&vb->balloon_lock);
 	/* We can't release more pages than taken */
@@ -210,7 +342,11 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 		page = balloon_page_dequeue(vb_dev_info);
 		if (!page)
 			break;
-		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
+		if (use_sg)
+			xb_set_page(vb, page, &pfn_min, &pfn_max);
+		else
+			set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
+
 		list_add(&page->lru, &pages);
 		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 	}
@@ -221,8 +357,12 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 	 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 	 * is true, we *have* to do it in this order
 	 */
-	if (vb->num_pfns != 0)
-		tell_host(vb, vb->deflate_vq);
+	if (vb->num_pfns) {
+		if (use_sg)
+			tell_host_sgs(vb, vb->deflate_vq, pfn_min, pfn_max);
+		else
+			tell_host(vb, vb->deflate_vq);
+	}
 	release_pages_balloon(vb, &pages);
 	mutex_unlock(&vb->balloon_lock);
 	return num_freed_pages;
@@ -441,6 +581,7 @@ static int init_vqs(struct virtio_balloon *vb)
 }
 
 #ifdef CONFIG_BALLOON_COMPACTION
+
 /*
  * virtballoon_migratepage - perform the balloon page migration on behalf of
  *			     a compation thread.     (called under page lock)
@@ -464,6 +605,7 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 {
 	struct virtio_balloon *vb = container_of(vb_dev_info,
 			struct virtio_balloon, vb_dev_info);
+	bool use_sg = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_SG);
 	unsigned long flags;
 
 	/*
@@ -485,16 +627,24 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 	vb_dev_info->isolated_pages--;
 	__count_vm_event(BALLOON_MIGRATE);
 	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
-	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
-	set_page_pfns(vb, vb->pfns, newpage);
-	tell_host(vb, vb->inflate_vq);
-
+	if (use_sg) {
+		send_balloon_page_sg(vb, vb->inflate_vq, page_address(newpage),
+				     PAGE_SIZE, false);
+	} else {
+		vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
+		set_page_pfns(vb, vb->pfns, newpage);
+		tell_host(vb, vb->inflate_vq);
+	}
 	/* balloon's page migration 2nd step -- deflate "page" */
 	balloon_page_delete(page);
-	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
-	set_page_pfns(vb, vb->pfns, page);
-	tell_host(vb, vb->deflate_vq);
-
+	if (use_sg) {
+		send_balloon_page_sg(vb, vb->deflate_vq, page_address(page),
+				     PAGE_SIZE, false);
+	} else {
+		vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
+		set_page_pfns(vb, vb->pfns, page);
+		tell_host(vb, vb->deflate_vq);
+	}
 	mutex_unlock(&vb->balloon_lock);
 
 	put_page(page); /* balloon reference */
@@ -553,6 +703,9 @@ static int virtballoon_probe(struct virtio_device *vdev)
 	if (err)
 		goto out_free_vb;
 
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_SG))
+		xb_init(&vb->page_xb);
+
 	vb->nb.notifier_call = virtballoon_oom_notify;
 	vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
 	err = register_oom_notifier(&vb->nb);
@@ -669,6 +822,7 @@ static unsigned int features[] = {
 	VIRTIO_BALLOON_F_MUST_TELL_HOST,
 	VIRTIO_BALLOON_F_STATS_VQ,
 	VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
+	VIRTIO_BALLOON_F_SG,
 };
 
 static struct virtio_driver virtio_balloon_driver = {
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index 343d7dd..37780a7 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -34,6 +34,7 @@
 #define VIRTIO_BALLOON_F_MUST_TELL_HOST	0 /* Tell before reclaiming pages */
 #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */
 #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
+#define VIRTIO_BALLOON_F_SG		3 /* Use sg instead of PFN lists */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12
-- 
2.7.4

[toc] | [prev] | [next] | [standalone]

#1742962 — Re: [PATCH v16 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG

Looks good to me. minor comments below.

On Sat, Sep 30, 2017 at 12:05:52PM +0800, Wei Wang wrote:
> @@ -141,13 +146,128 @@ static void set_page_pfns(struct virtio_balloon *vb,
>  					  page_to_balloon_pfn(page) + i);
>  }
>  
> +
> +static void kick_and_wait(struct virtqueue *vq, wait_queue_head_t wq_head)
> +{
> +	unsigned int len;
> +
> +	virtqueue_kick(vq);
> +	wait_event(wq_head, virtqueue_get_buf(vq, &len));
> +}
> +
> +static int add_one_sg(struct virtqueue *vq, void *addr, uint32_t size)
> +{
> +	struct scatterlist sg;
> +	unsigned int len;
> +
> +	sg_init_one(&sg, addr, size);
> +
> +	/* Detach all the used buffers from the vq */
> +	while (virtqueue_get_buf(vq, &len))
> +		;
> +
> +	return virtqueue_add_inbuf(vq, &sg, 1, vq, GFP_KERNEL);
> +}
> +
> +static int send_balloon_page_sg(struct virtio_balloon *vb,
> +				 struct virtqueue *vq,
> +				 void *addr,
> +				 uint32_t size,
> +				 bool batch)
> +{
> +	int err;
> +
> +	err = add_one_sg(vq, addr, size);
> +
> +	/* If batchng is requested, we batch till the vq is full */

typo

> +	if (!batch || !vq->num_free)
> +		kick_and_wait(vq, vb->acked);
> +
> +	return err;
> +}

If add_one_sg fails, kick_and_wait will hang forever.

The reason this might work in because
1. with 1 sg there are no memory allocations
2. if adding fails on vq full, then something
   is in queue and will wake up kick_and_wait.

So in short this is expected to never fail.
How about a BUG_ON here then?
And make it void, and add a comment with above explanation.

> +
> +/*
> + * Send balloon pages in sgs to host. The balloon pages are recorded in the
> + * page xbitmap. Each bit in the bitmap corresponds to a page of PAGE_SIZE.
> + * The page xbitmap is searched for continuous "1" bits, which correspond
> + * to continuous pages, to chunk into sgs.
> + *
> + * @page_xb_start and @page_xb_end form the range of bits in the xbitmap that
> + * need to be searched.
> + */
> +static void tell_host_sgs(struct virtio_balloon *vb,
> +			  struct virtqueue *vq,
> +			  unsigned long page_xb_start,
> +			  unsigned long page_xb_end)
> +{
> +	unsigned long sg_pfn_start, sg_pfn_end;
> +	void *sg_addr;
> +	uint32_t sg_len, sg_max_len = round_down(UINT_MAX, PAGE_SIZE);
> +	int err = 0;
> +
> +	sg_pfn_start = page_xb_start;
> +	while (sg_pfn_start < page_xb_end) {
> +		sg_pfn_start = xb_find_next_set_bit(&vb->page_xb, sg_pfn_start,
> +						    page_xb_end);
> +		if (sg_pfn_start == page_xb_end + 1)
> +			break;
> +		sg_pfn_end = xb_find_next_zero_bit(&vb->page_xb,
> +						   sg_pfn_start + 1,
> +						   page_xb_end);
> +		sg_addr = (void *)pfn_to_kaddr(sg_pfn_start);
> +		sg_len = (sg_pfn_end - sg_pfn_start) << PAGE_SHIFT;
> +		while (sg_len > sg_max_len) {
> +			err = send_balloon_page_sg(vb, vq, sg_addr, sg_max_len,
> +						   true);
> +			if (unlikely(err < 0))
> +				goto err_out;
> +			sg_addr += sg_max_len;
> +			sg_len -= sg_max_len;
> +		}
> +		err = send_balloon_page_sg(vb, vq, sg_addr, sg_len, true);
> +		if (unlikely(err < 0))
> +			goto err_out;
> +		sg_pfn_start = sg_pfn_end + 1;
> +	}
> +
> +	/*
> +	 * The last few sgs may not reach the batch size, but need a kick to
> +	 * notify the device to handle them.
> +	 */
> +	if (vq->num_free != virtqueue_get_vring_size(vq))
> +		kick_and_wait(vq, vb->acked);
> +
> +	xb_clear_bit_range(&vb->page_xb, page_xb_start, page_xb_end);
> +	return;
> +
> +err_out:
> +	dev_warn(&vb->vdev->dev, "%s failure: %d\n", __func__, err);

so fundamentally just make send_balloon_page_sg void then.

> +}
> +
> +static inline void xb_set_page(struct virtio_balloon *vb,
> +			       struct page *page,
> +			       unsigned long *pfn_min,
> +			       unsigned long *pfn_max)
> +{
> +	unsigned long pfn = page_to_pfn(page);
> +
> +	*pfn_min = min(pfn, *pfn_min);
> +	*pfn_max = max(pfn, *pfn_max);
> +	xb_preload(GFP_KERNEL);
> +	xb_set_bit(&vb->page_xb, pfn);
> +	xb_preload_end();
> +}
> +
>  static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
>  {
>  	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
>  	unsigned num_allocated_pages;
> +	bool use_sg = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_SG);
> +	unsigned long pfn_max = 0, pfn_min = ULONG_MAX;
>  
>  	/* We can only do one array worth at a time. */
> -	num = min(num, ARRAY_SIZE(vb->pfns));
> +	if (!use_sg)
> +		num = min(num, ARRAY_SIZE(vb->pfns));
>  
>  	mutex_lock(&vb->balloon_lock);
>  	for (vb->num_pfns = 0; vb->num_pfns < num;
> @@ -162,7 +282,12 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
>  			msleep(200);
>  			break;
>  		}
> -		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> +
> +		if (use_sg)
> +			xb_set_page(vb, page, &pfn_min, &pfn_max);
> +		else
> +			set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> +
>  		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
>  		if (!virtio_has_feature(vb->vdev,
>  					VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> @@ -171,8 +296,12 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
>  
>  	num_allocated_pages = vb->num_pfns;
>  	/* Did we get any? */
> -	if (vb->num_pfns != 0)
> -		tell_host(vb, vb->inflate_vq);
> +	if (vb->num_pfns) {
> +		if (use_sg)
> +			tell_host_sgs(vb, vb->inflate_vq, pfn_min, pfn_max);
> +		else
> +			tell_host(vb, vb->inflate_vq);
> +	}
>  	mutex_unlock(&vb->balloon_lock);
>  
>  	return num_allocated_pages;
> @@ -198,9 +327,12 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
>  	struct page *page;
>  	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
>  	LIST_HEAD(pages);
> +	bool use_sg = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_SG);
> +	unsigned long pfn_max = 0, pfn_min = ULONG_MAX;
>  
> -	/* We can only do one array worth at a time. */
> -	num = min(num, ARRAY_SIZE(vb->pfns));
> +	/* Traditionally, we can only do one array worth at a time. */
> +	if (!use_sg)
> +		num = min(num, ARRAY_SIZE(vb->pfns));
>  
>  	mutex_lock(&vb->balloon_lock);
>  	/* We can't release more pages than taken */
> @@ -210,7 +342,11 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
>  		page = balloon_page_dequeue(vb_dev_info);
>  		if (!page)
>  			break;
> -		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> +		if (use_sg)
> +			xb_set_page(vb, page, &pfn_min, &pfn_max);
> +		else
> +			set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> +
>  		list_add(&page->lru, &pages);
>  		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
>  	}
> @@ -221,8 +357,12 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
>  	 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
>  	 * is true, we *have* to do it in this order
>  	 */
> -	if (vb->num_pfns != 0)
> -		tell_host(vb, vb->deflate_vq);
> +	if (vb->num_pfns) {
> +		if (use_sg)
> +			tell_host_sgs(vb, vb->deflate_vq, pfn_min, pfn_max);
> +		else
> +			tell_host(vb, vb->deflate_vq);
> +	}
>  	release_pages_balloon(vb, &pages);
>  	mutex_unlock(&vb->balloon_lock);
>  	return num_freed_pages;
> @@ -441,6 +581,7 @@ static int init_vqs(struct virtio_balloon *vb)
>  }
>  
>  #ifdef CONFIG_BALLOON_COMPACTION
> +
>  /*
>   * virtballoon_migratepage - perform the balloon page migration on behalf of
>   *			     a compation thread.     (called under page lock)
> @@ -464,6 +605,7 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
>  {
>  	struct virtio_balloon *vb = container_of(vb_dev_info,
>  			struct virtio_balloon, vb_dev_info);
> +	bool use_sg = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_SG);
>  	unsigned long flags;
>  
>  	/*
> @@ -485,16 +627,24 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
>  	vb_dev_info->isolated_pages--;
>  	__count_vm_event(BALLOON_MIGRATE);
>  	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
> -	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> -	set_page_pfns(vb, vb->pfns, newpage);
> -	tell_host(vb, vb->inflate_vq);
> -
> +	if (use_sg) {
> +		send_balloon_page_sg(vb, vb->inflate_vq, page_address(newpage),
> +				     PAGE_SIZE, false);
> +	} else {
> +		vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> +		set_page_pfns(vb, vb->pfns, newpage);
> +		tell_host(vb, vb->inflate_vq);
> +	}
>  	/* balloon's page migration 2nd step -- deflate "page" */
>  	balloon_page_delete(page);
> -	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> -	set_page_pfns(vb, vb->pfns, page);
> -	tell_host(vb, vb->deflate_vq);
> -
> +	if (use_sg) {
> +		send_balloon_page_sg(vb, vb->deflate_vq, page_address(page),
> +				     PAGE_SIZE, false);
> +	} else {
> +		vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> +		set_page_pfns(vb, vb->pfns, page);
> +		tell_host(vb, vb->deflate_vq);
> +	}
>  	mutex_unlock(&vb->balloon_lock);
>  
>  	put_page(page); /* balloon reference */
> @@ -553,6 +703,9 @@ static int virtballoon_probe(struct virtio_device *vdev)
>  	if (err)
>  		goto out_free_vb;
>  
> +	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_SG))
> +		xb_init(&vb->page_xb);
> +
>  	vb->nb.notifier_call = virtballoon_oom_notify;
>  	vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
>  	err = register_oom_notifier(&vb->nb);
> @@ -669,6 +822,7 @@ static unsigned int features[] = {
>  	VIRTIO_BALLOON_F_MUST_TELL_HOST,
>  	VIRTIO_BALLOON_F_STATS_VQ,
>  	VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
> +	VIRTIO_BALLOON_F_SG,
>  };
>  
>  static struct virtio_driver virtio_balloon_driver = {
> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> index 343d7dd..37780a7 100644
> --- a/include/uapi/linux/virtio_balloon.h
> +++ b/include/uapi/linux/virtio_balloon.h
> @@ -34,6 +34,7 @@
>  #define VIRTIO_BALLOON_F_MUST_TELL_HOST	0 /* Tell before reclaiming pages */
>  #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */
>  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
> +#define VIRTIO_BALLOON_F_SG		3 /* Use sg instead of PFN lists */
>  
>  /* Size of a PFN in the balloon interface. */
>  #define VIRTIO_BALLOON_PFN_SHIFT 12
> -- 
> 2.7.4

[toc] | [prev] | [next] | [standalone]

#1743180 — RE: [PATCH v16 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG

On Monday, October 2, 2017 12:30 PM, Michael S. Tsirkin wrote:
> On Sat, Sep 30, 2017 at 12:05:52PM +0800, Wei Wang wrote:
> > +static int send_balloon_page_sg(struct virtio_balloon *vb,
> > +				 struct virtqueue *vq,
> > +				 void *addr,
> > +				 uint32_t size,
> > +				 bool batch)
> > +{
> > +	int err;
> > +
> > +	err = add_one_sg(vq, addr, size);
> > +
> > +	/* If batchng is requested, we batch till the vq is full */
> 
> typo
> 
> > +	if (!batch || !vq->num_free)
> > +		kick_and_wait(vq, vb->acked);
> > +
> > +	return err;
> > +}
> 
> If add_one_sg fails, kick_and_wait will hang forever.
> 
> The reason this might work in because
> 1. with 1 sg there are no memory allocations 2. if adding fails on vq full, then
> something
>    is in queue and will wake up kick_and_wait.
> 
> So in short this is expected to never fail.
> How about a BUG_ON here then?
> And make it void, and add a comment with above explanation.
> 


Yes, agree that this wouldn't fail - the worker thread performing the ballooning operations has been put into sleep when the vq is full, so I think there shouldn't be anyone else to put more sgs onto the vq then.
Btw, not sure if we need to mention memory allocation in the comment, I found virtqueue_add() doesn't return any error when allocation (for indirect desc-s) fails - it simply avoids the use of indirect desc.

What do you think of the following? 

err = add_one_sg(vq, addr, size);
/* 
  * This is expected to never fail: there is always at least 1 entry available on the vq,
  * because when the vq is full the worker thread that adds the sg will be put into
  * sleep until at least 1 entry is available to use.
  */
BUG_ON(err);

Best,
Wei



 

[toc] | [prev] | [next] | [standalone]

#1742803

Hello,

where i can found the patch in git.kernel.org ?

Best regards
Damian


Am Samstag, den 30.09.2017, 12:05 +0800 schrieb Wei Wang:
> This patch series enhances the existing virtio-balloon with the
> following
> new features:
> 1) fast ballooning: transfer ballooned pages between the guest and
> host in
> chunks using sgs, instead of one array each time; and
> 2) free page block reporting: a new virtqueue to report guest free
> pages
> to the host.
> 
> The second feature can be used to accelerate live migration of VMs.
> Here
> are some details:
> 
> Live migration needs to transfer the VM's memory from the source
> machine
> to the destination round by round. For the 1st round, all the VM's
> memory
> is transferred. From the 2nd round, only the pieces of memory that
> were
> written by the guest (after the 1st round) are transferred. One
> method
> that is popularly used by the hypervisor to track which part of
> memory is
> written is to write-protect all the guest memory.
> 
> The second feature enables the optimization of the 1st round memory
> transfer - the hypervisor can skip the transfer of guest free pages
> in the
> 1st round. It is not concerned that the memory pages are used after
> they
> are given to the hypervisor as a hint of the free pages, because they
> will
> be tracked by the hypervisor and transferred in the next round if
> they are
> used and written.
> 
> Change Log:
> v15->v16:
> 1) mm: stop reporting the free pfn range if the callback returns
> false;
> 2) mm: move some implementaion of walk_free_mem_block into a function
> to
> make the code layout looks better;
> 3) xbitmap: added some optimizations suggested by Matthew, please
> refer to
> the ChangLog in the xbitmap patch for details.
> 4) xbitmap: added a test suite
> 5) virtio-balloon: bail out with a warning when virtqueue_add_inbuf
> returns
> an error
> 6) virtio-balloon: some small code re-arrangement, e.g. detachinf
> used buf
> from the vq before adding a new buf
> 
> v14->v15:
> 1) mm: make the report callback return a bool value - returning 1 to
> stop
> walking through the free page list.
> 2) virtio-balloon: batching sgs of balloon pages till the vq is full
> 3) virtio-balloon: create a new workqueue, rather than using the
> default
> system_wq, to queue the free page reporting work item.
> 4) virtio-balloon: add a ctrl_vq to be a central control plane which
> will
> handle all the future control related commands between the host and
> guest.
> Add free page report as the first feature controlled under ctrl_vq,
> and
> the free_page_vq is a data plane vq dedicated to the transmission of
> free
> page blocks.
> 
> v13->v14:
> 1) xbitmap: move the code from lib/radix-tree.c to lib/xbitmap.c.
> 2) xbitmap: consolidate the implementation of xb_bit_set/clear/test
> into
> one xb_bit_ops.
> 3) xbitmap: add documents for the exported APIs.
> 4) mm: rewrite the function to walk through free page blocks.
> 5) virtio-balloon: when reporting a free page blcok to the device, if
> the
> vq is full (less likey to happen in practice), just skip reporting
> this
> block, instead of busywaiting till an entry gets released.
> 6) virtio-balloon: fail the probe function if adding the signal buf
> in
> init_vqs fails.
> 
> v12->v13:
> 1) mm: use a callback function to handle the the free page blocks
> from the
> report function. This avoids exposing the zone internal to a kernel
> module.
> 2) virtio-balloon: send balloon pages or a free page block using a
> single
> sg each time. This has the benefits of simpler implementation with no
> new
> APIs.
> 3) virtio-balloon: the free_page_vq is used to report free pages only
> (no
> multiple usages interleaving)
> 4) virtio-balloon: Balloon pages and free page blocks are sent via
> input
> sgs, and the completion signal to the host is sent via an output sg.
> 
> v11->v12:
> 1) xbitmap: use the xbitmap from Matthew Wilcox to record ballooned
> pages.
> 2) virtio-ring: enable the driver to build up a desc chain using
> vring
> desc.
> 3) virtio-ring: Add locking to the existing START_USE() and END_USE()
> macro to lock/unlock the vq when a vq operation starts/ends.
> 4) virtio-ring: add virtqueue_kick_sync() and virtqueue_kick_async()
> 5) virtio-balloon: describe chunks of ballooned pages and free pages
> blocks directly using one or more chains of desc from the vq.
> 
> v10->v11:
> 1) virtio_balloon: use vring_desc to describe a chunk;
> 2) virtio_ring: support to add an indirect desc table to virtqueue;
> 3)  virtio_balloon: use cmdq to report guest memory statistics.
> 
> v9->v10:
> 1) mm: put report_unused_page_block() under CONFIG_VIRTIO_BALLOON;
> 2) virtio-balloon: add virtballoon_validate();
> 3) virtio-balloon: msg format change;
> 4) virtio-balloon: move miscq handling to a task on
> system_freezable_wq;
> 5) virtio-balloon: code cleanup.
> 
> v8->v9:
> 1) Split the two new features, VIRTIO_BALLOON_F_BALLOON_CHUNKS and
> VIRTIO_BALLOON_F_MISC_VQ, which were mixed together in the previous
> implementation;
> 2) Simpler function to get the free page block.
> 
> v7->v8:
> 1) Use only one chunk format, instead of two.
> 2) re-write the virtio-balloon implementation patch.
> 3) commit changes
> 4) patch re-org
> 
> Matthew Wilcox (2):
>   lib/xbitmap: Introduce xbitmap
>   radix tree test suite: add tests for xbitmap
> 
> Wei Wang (3):
>   virtio-balloon: VIRTIO_BALLOON_F_SG
>   mm: support reporting free page blocks
>   virtio-balloon: VIRTIO_BALLOON_F_CTRL_VQ
> 
>  drivers/virtio/virtio_balloon.c         | 437
> +++++++++++++++++++++++++++++---
>  include/linux/mm.h                      |   6 +
>  include/linux/radix-tree.h              |   2 +
>  include/linux/xbitmap.h                 |  66 +++++
>  include/uapi/linux/virtio_balloon.h     |  16 ++
>  lib/Makefile                            |   2 +-
>  lib/radix-tree.c                        |  42 ++-
>  lib/xbitmap.c                           | 264 +++++++++++++++++++
>  mm/page_alloc.c                         |  91 +++++++
>  tools/include/linux/bitmap.h            |  34 +++
>  tools/include/linux/kernel.h            |   2 +
>  tools/testing/radix-tree/Makefile       |   7 +-
>  tools/testing/radix-tree/linux/kernel.h |   2 -
>  tools/testing/radix-tree/main.c         |   5 +
>  tools/testing/radix-tree/test.h         |   1 +
>  tools/testing/radix-tree/xbitmap.c      | 269 ++++++++++++++++++++
>  16 files changed, 1203 insertions(+), 43 deletions(-)
>  create mode 100644 include/linux/xbitmap.h
>  create mode 100644 lib/xbitmap.c
>  create mode 100644 tools/testing/radix-tree/xbitmap.c
> 

[toc] | [prev] | [next] | [standalone]

#1742810

Hello,

where i can found the patch in git.kernel.org ?


Am Samstag, den 30.09.2017, 12:05 +0800 schrieb Wei Wang:
> This patch series enhances the existing virtio-balloon with the
> following
> new features:
> 1) fast ballooning: transfer ballooned pages between the guest and
> host in
> chunks using sgs, instead of one array each time; and
> 2) free page block reporting: a new virtqueue to report guest free
> pages
> to the host.
> 
> The second feature can be used to accelerate live migration of VMs.
> Here
> are some details:
> 
> Live migration needs to transfer the VM's memory from the source
> machine
> to the destination round by round. For the 1st round, all the VM's
> memory
> is transferred. From the 2nd round, only the pieces of memory that
> were
> written by the guest (after the 1st round) are transferred. One
> method
> that is popularly used by the hypervisor to track which part of
> memory is
> written is to write-protect all the guest memory.
> 
> The second feature enables the optimization of the 1st round memory
> transfer - the hypervisor can skip the transfer of guest free pages
> in the
> 1st round. It is not concerned that the memory pages are used after
> they
> are given to the hypervisor as a hint of the free pages, because they
> will
> be tracked by the hypervisor and transferred in the next round if
> they are
> used and written.
> 
> Change Log:
> v15->v16:
> 1) mm: stop reporting the free pfn range if the callback returns
> false;
> 2) mm: move some implementaion of walk_free_mem_block into a function
> to
> make the code layout looks better;
> 3) xbitmap: added some optimizations suggested by Matthew, please
> refer to
> the ChangLog in the xbitmap patch for details.
> 4) xbitmap: added a test suite
> 5) virtio-balloon: bail out with a warning when virtqueue_add_inbuf
> returns
> an error
> 6) virtio-balloon: some small code re-arrangement, e.g. detachinf
> used buf
> from the vq before adding a new buf
> 
> v14->v15:
> 1) mm: make the report callback return a bool value - returning 1 to
> stop
> walking through the free page list.
> 2) virtio-balloon: batching sgs of balloon pages till the vq is full
> 3) virtio-balloon: create a new workqueue, rather than using the
> default
> system_wq, to queue the free page reporting work item.
> 4) virtio-balloon: add a ctrl_vq to be a central control plane which
> will
> handle all the future control related commands between the host and
> guest.
> Add free page report as the first feature controlled under ctrl_vq,
> and
> the free_page_vq is a data plane vq dedicated to the transmission of
> free
> page blocks.
> 
> v13->v14:
> 1) xbitmap: move the code from lib/radix-tree.c to lib/xbitmap.c.
> 2) xbitmap: consolidate the implementation of xb_bit_set/clear/test
> into
> one xb_bit_ops.
> 3) xbitmap: add documents for the exported APIs.
> 4) mm: rewrite the function to walk through free page blocks.
> 5) virtio-balloon: when reporting a free page blcok to the device, if
> the
> vq is full (less likey to happen in practice), just skip reporting
> this
> block, instead of busywaiting till an entry gets released.
> 6) virtio-balloon: fail the probe function if adding the signal buf
> in
> init_vqs fails.
> 
> v12->v13:
> 1) mm: use a callback function to handle the the free page blocks
> from the
> report function. This avoids exposing the zone internal to a kernel
> module.
> 2) virtio-balloon: send balloon pages or a free page block using a
> single
> sg each time. This has the benefits of simpler implementation with no
> new
> APIs.
> 3) virtio-balloon: the free_page_vq is used to report free pages only
> (no
> multiple usages interleaving)
> 4) virtio-balloon: Balloon pages and free page blocks are sent via
> input
> sgs, and the completion signal to the host is sent via an output sg.
> 
> v11->v12:
> 1) xbitmap: use the xbitmap from Matthew Wilcox to record ballooned
> pages.
> 2) virtio-ring: enable the driver to build up a desc chain using
> vring
> desc.
> 3) virtio-ring: Add locking to the existing START_USE() and END_USE()
> macro to lock/unlock the vq when a vq operation starts/ends.
> 4) virtio-ring: add virtqueue_kick_sync() and virtqueue_kick_async()
> 5) virtio-balloon: describe chunks of ballooned pages and free pages
> blocks directly using one or more chains of desc from the vq.
> 
> v10->v11:
> 1) virtio_balloon: use vring_desc to describe a chunk;
> 2) virtio_ring: support to add an indirect desc table to virtqueue;
> 3)  virtio_balloon: use cmdq to report guest memory statistics.
> 
> v9->v10:
> 1) mm: put report_unused_page_block() under CONFIG_VIRTIO_BALLOON;
> 2) virtio-balloon: add virtballoon_validate();
> 3) virtio-balloon: msg format change;
> 4) virtio-balloon: move miscq handling to a task on
> system_freezable_wq;
> 5) virtio-balloon: code cleanup.
> 
> v8->v9:
> 1) Split the two new features, VIRTIO_BALLOON_F_BALLOON_CHUNKS and
> VIRTIO_BALLOON_F_MISC_VQ, which were mixed together in the previous
> implementation;
> 2) Simpler function to get the free page block.
> 
> v7->v8:
> 1) Use only one chunk format, instead of two.
> 2) re-write the virtio-balloon implementation patch.
> 3) commit changes
> 4) patch re-org
> 
> Matthew Wilcox (2):
>   lib/xbitmap: Introduce xbitmap
>   radix tree test suite: add tests for xbitmap
> 
> Wei Wang (3):
>   virtio-balloon: VIRTIO_BALLOON_F_SG
>   mm: support reporting free page blocks
>   virtio-balloon: VIRTIO_BALLOON_F_CTRL_VQ
> 
>  drivers/virtio/virtio_balloon.c         | 437
> +++++++++++++++++++++++++++++---
>  include/linux/mm.h                      |   6 +
>  include/linux/radix-tree.h              |   2 +
>  include/linux/xbitmap.h                 |  66 +++++
>  include/uapi/linux/virtio_balloon.h     |  16 ++
>  lib/Makefile                            |   2 +-
>  lib/radix-tree.c                        |  42 ++-
>  lib/xbitmap.c                           | 264 +++++++++++++++++++
>  mm/page_alloc.c                         |  91 +++++++
>  tools/include/linux/bitmap.h            |  34 +++
>  tools/include/linux/kernel.h            |   2 +
>  tools/testing/radix-tree/Makefile       |   7 +-
>  tools/testing/radix-tree/linux/kernel.h |   2 -
>  tools/testing/radix-tree/main.c         |   5 +
>  tools/testing/radix-tree/test.h         |   1 +
>  tools/testing/radix-tree/xbitmap.c      | 269 ++++++++++++++++++++
>  16 files changed, 1203 insertions(+), 43 deletions(-)
>  create mode 100644 include/linux/xbitmap.h
>  create mode 100644 lib/xbitmap.c
>  create mode 100644 tools/testing/radix-tree/xbitmap.c
> 

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web