[PATCH for QEMU v2] virtio-balloon: Add option cont-pages to set VIRTIO_BALLOON_VQ_INFLATE_CONT

Hui Zhu
2020-03-22T16:06:29Z

If the guest kernel has many fragmentation pages, use virtio_balloon
will split THP of QEMU when it calls MADV_DONTNEED madvise to release
the balloon pages.
Set option cont-pages to on will open flags VIRTIO_BALLOON_VQ_INFLATE_CONT
and set continuous pages order to THP order.
Then It will get continuous pages PFN from VQ icvq use use madvise
MADV_DONTNEED release the THP page.
This will handle the THP split issue.

Signed-off-by: Hui Zhu <teawaterz@linux.alibaba.com>
---
hw/virtio/virtio-balloon.c | 32 +++++++++++++++++++++----
include/hw/virtio/virtio-balloon.h | 4 +++-
include/standard-headers/linux/virtio_balloon.h | 4 ++++
3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index a4729f7..88bdaca 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -34,6 +34,7 @@
#include "hw/virtio/virtio-access.h"

#define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT)
+#define CONT_PAGES_ORDER 9

typedef struct PartiallyBalloonedPage {
ram_addr_t base_gpa;
@@ -65,7 +66,8 @@ static bool virtio_balloon_pbp_matches(PartiallyBalloonedPage *pbp,

static void balloon_inflate_page(VirtIOBalloon *balloon,
MemoryRegion *mr, hwaddr mr_offset,
- PartiallyBalloonedPage *pbp)
+ PartiallyBalloonedPage *pbp,
+ bool is_cont_pages)
{
void *addr = memory_region_get_ram_ptr(mr) + mr_offset;
ram_addr_t rb_offset, rb_aligned_offset, base_gpa;
@@ -76,6 +78,13 @@ static void balloon_inflate_page(VirtIOBalloon *balloon,
/* XXX is there a better way to get to the RAMBlock than via a
* host address? */
rb = qemu_ram_block_from_host(addr, false, &rb_offset);
+
+ if (is_cont_pages) {
+ ram_block_discard_range(rb, rb_offset,
+ BALLOON_PAGE_SIZE << CONT_PAGES_ORDER);
+ return;
+ }
+
rb_page_size = qemu_ram_pagesize(rb);

if (rb_page_size == BALLOON_PAGE_SIZE) {
@@ -361,9 +370,10 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
trace_virtio_balloon_handle_output(memory_region_name(section.mr),
pa);
if (!qemu_balloon_is_inhibited()) {
- if (vq == s->ivq) {
+ if (vq == s->ivq || vq == s->icvq) {
balloon_inflate_page(s, section.mr,
- section.offset_within_region, &pbp);
+ section.offset_within_region, &pbp,
+ vq == s->icvq);
} else if (vq == s->dvq) {
balloon_deflate_page(s, section.mr, section.offset_within_region);
} else {
@@ -618,9 +628,12 @@ static size_t virtio_balloon_config_size(VirtIOBalloon *s)
if (s->qemu_4_0_config_size) {
return sizeof(struct virtio_balloon_config);
}
- if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON)) {
+ if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_CONT_PAGES)) {
return sizeof(struct virtio_balloon_config);
}
+ if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON)) {
+ return offsetof(struct virtio_balloon_config, pages_order);
+ }
if (virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
return offsetof(struct virtio_balloon_config, poison_val);
}
@@ -646,6 +659,10 @@ static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
cpu_to_le32(VIRTIO_BALLOON_CMD_ID_DONE);
}

+ if (virtio_has_feature(dev->host_features, VIRTIO_BALLOON_F_CONT_PAGES)) {
+ config.pages_order = cpu_to_le32(CONT_PAGES_ORDER);
+ }
+
trace_virtio_balloon_get_config(config.num_pages, config.actual);
memcpy(config_data, &config, virtio_balloon_config_size(dev));
}
@@ -816,6 +833,11 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
virtio_error(vdev, "iothread is missing");
}
}
+
+ if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_CONT_PAGES)) {
+ s->icvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
+ }
+
reset_stats(s);
}

@@ -916,6 +938,8 @@ static Property virtio_balloon_properties[] = {
VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false),
DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features,
VIRTIO_BALLOON_F_FREE_PAGE_HINT, false),
+ DEFINE_PROP_BIT("cont-pages", VirtIOBalloon, host_features,
+ VIRTIO_BALLOON_F_CONT_PAGES, false),
/* QEMU 4.0 accidentally changed the config size even when free-page-hint
* is disabled, resulting in QEMU 3.1 migration incompatibility. This
* property retains this quirk for QEMU 4.1 machine types.
diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index d1c968d..61d2419 100644
--- a/include/hw/virtio/virtio-balloon.h
+++ b/include/hw/virtio/virtio-balloon.h
@@ -42,7 +42,7 @@ enum virtio_balloon_free_page_report_status {

typedef struct VirtIOBalloon {
VirtIODevice parent_obj;
- VirtQueue *ivq, *dvq, *svq, *free_page_vq;
+ VirtQueue *ivq, *dvq, *svq, *free_page_vq, *icvq;
uint32_t free_page_report_status;
uint32_t num_pages;
uint32_t actual;
@@ -70,6 +70,8 @@ typedef struct VirtIOBalloon {
uint32_t host_features;

bool qemu_4_0_config_size;
+
+ uint32_t pages_order;
} VirtIOBalloon;

#endif
diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h
index 9375ca2..ee18be7 100644
--- a/include/standard-headers/linux/virtio_balloon.h
+++ b/include/standard-headers/linux/virtio_balloon.h
@@ -36,6 +36,8 @@
#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
#define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */
#define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */
+#define VIRTIO_BALLOON_F_CONT_PAGES 5 /* VQ to report continuous pages */
+

/* Size of a PFN in the balloon interface. */
#define VIRTIO_BALLOON_PFN_SHIFT 12
@@ -51,6 +53,8 @@ struct virtio_balloon_config {
uint32_t free_page_report_cmd_id;
/* Stores PAGE_POISON if page poisoning is in use */
uint32_t poison_val;
+ /* Pages order if VIRTIO_BALLOON_F_CONT_PAGES is set */
+ uint32_t pages_order;
};

#define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */
--
2.7.4