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[Qemu-devel] [PATCH] memory: unref the memory region in simplify flatvie

From: Wang King
Subject: [Qemu-devel] [PATCH] memory: unref the memory region in simplify flatview
Date: Fri, 12 Jul 2019 14:52:41 +0800

From: King Wang<address@hidden>

The memory region reference is increased when insert a range
into flatview range array, then decreased by destroy flatview.
If some flat range merged by flatview_simplify, the memory region
reference can not be decreased by destroy flatview any more.

In this case, start virtual machine by the command line:
-name guest=ubuntu,debug-threads=on
-machine pc,accel=kvm,usb=off,dump-guest-core=off
-cpu host
-m 16384
-realtime mlock=off
-smp 8,sockets=2,cores=4,threads=1
-numa node,nodeid=0,cpus=0-3,memdev=ram-node0
-numa node,nodeid=1,cpus=4-7,memdev=ram-node1
-rtc base=utc
-boot strict=on
-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2
-device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x2
-device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x3
-chardev pty,id=charserial0
-device isa-serial,chardev=charserial0,id=serial0
-device usb-tablet,id=input0,bus=usb.0,port=1
-device VGA,id=video0,vgamem_mb=16,bus=pci.0,addr=0x5
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6
-msg timestamp=on

And run the script in guest OS:
while true
    setpci -s 00:06.0 04.b=03
        setpci -s 00:06.0 04.b=07

I found the reference of node0 HostMemoryBackendFile is a big one.
(gdb) p numa_info[0]->node_memdev->parent.ref
$6 = 1636278

Signed-off-by: King Wang<address@hidden>
 memory.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/memory.c b/memory.c
index 480f3d989b..d8d42bdff8 100644
--- a/memory.c
+++ b/memory.c
@@ -321,7 +321,7 @@ static bool can_merge(FlatRange *r1, FlatRange *r2)
 /* Attempt to simplify a view by merging adjacent ranges */
 static void flatview_simplify(FlatView *view)
-    unsigned i, j;
+    unsigned i, j, k;
     i = 0;
     while (i < view->nr) {
@@ -332,6 +332,9 @@ static void flatview_simplify(FlatView *view)
+        for (k = i; k < j; k++) {
+            memory_region_unref(view->ranges[k].mr);
+        }
         memmove(&view->ranges[i], &view->ranges[j],
                 (view->nr - j) * sizeof(view->ranges[j]));
         view->nr -= j - i;

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