[Qemu-devel] [Bug 1288620] Re: memory leak with default NIC model

[Stefan Weil]

Please try to reproduce this with a debug built (configure --enable-
debug) from latest QEMU. If it shows the same memory leak, you can try
to find the cause of this leak with valgrind:

valgrind --leak-check=full qemu-system-x86_64 -drive
file=windows_base_HDD.img,index=0,media=disk -enable-kvm -m 512M -vga
std -net nic,vlan=0 -net user,vlan=0 2>&1 | tee valgrind.log

As soon as you terminate the running qemu process, valgrind will write a 
protocol of all allocated memory. Leaks can usually be found quite easily in 
this protocol: after a long run, the leak will dominate any other memory 
allocation. If your executable still contains the full debug information, you 
will also see the exact line of source code which allocates repeatedly memory.
 
Please note that valgrind slows down your process by a factor of 10 to 20, so 
it takes some time to run Windows.

If valgrind does not work (which sometimes happens), you can attach a
debugger (gdb) to the running qemu process and try to detect the buggy
memory allocation by setting breakpoints on the memory allocator
functions (malloc or g_malloc, g_malloc0, g_new, g_new0).

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https://bugs.launchpad.net/bugs/1288620

Title:
  memory leak with default NIC model

Status in QEMU:
  New

Bug description:
  I have a Windows 7 SP1 Professional 64-bit installation on a QCOW2
  image with compat=1.1, which I launch via

  qemu-system-x86_64 -drive file=windows_base_HDD.img,index=0,media=disk
  -enable-kvm -m 512M -vga std -net nic,vlan=0 -net user,vlan=0

  As soon as I start using the network in any application — for example,
  visiting www.google.com in Internet Explorer — QEMU starts gobbling
  memory until the (host) kernel kills it because of an OOM condition.
  If I run the QEMU with the same options, but with model=e1000 option
  set for the NIC (i.e. -net -nic,vlan=0,model=e1000), I can use the
  network from the guest OS without any noticeable effect on QEMU's
  memory consumption.

  I do not have this problem when running QEMU with the exact same options (as 
above, without model=e1000) but with a Debian wheezy installation (on a QCOW 
image of the same format).  My host system in Ubuntu 13.10 x86_64, kernel image 
3.11.0-17-generic, but with the QEMU packages from trusty (the codename for the 
next release):
  Output of `dpkg -l \*qemu\* | grep '^ii'`:
  ii  ipxe-qemu                             1.0.0+git-20130710.936134e-0ubuntu1 
       all          Virtual package to support use of kvm-ipxe with qemu
  ii  qemu-keymaps                          1.7.0+dfsg-3ubuntu2                 
       all          QEMU keyboard maps
  ii  qemu-system-common                    1.7.0+dfsg-3ubuntu2                 
       amd64        QEMU full system emulation binaries (common files)
  ii  qemu-system-x86                       1.7.0+dfsg-3ubuntu2                 
       amd64        QEMU full system emulation binaries (x86)
  ii  qemu-utils                            1.7.0+dfsg-3ubuntu2                 
       amd64        QEMU utilities

  (If necessary, I can try to reproduce this with QEMU built from the
  upstream source or the latest source from version control.)

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