Am 26.03.2020 um 08:06 schrieb teawater [off-list ref]:

Ping.

On paid leave this week. Will try to have a look next week, but it could take a bit longer.

Cheers

Thanks,
Hui

quoted

2020年3月23日 00:04，Hui Zhu [off-list ref] 写道：

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 <redacted>
---
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