[libvirt-users] virDomainMemoryPeek: bad behavior under workload

[NoxDaFox]

Greetings,

I am working on a platform for analysis automation.
I need to run several Virtual Environments concurrently and record
information about their behavior.

I wrote some months ago about the capability of reading the Memory
during the Environment's execution (in paused state).
What do I need is the complete linear memory image, byte per byte,
nothing special; I will give this output to tools and parsers like
Volatility to get the value from it.

I looked around and the only way to get the memory in such a way is
using the QEMU monitor command `pmemsave`.
I am using libvirt through its Python bindings and the
virDomainQemuMonitorCommand seems not to be exposed by the API so, as
suggested in some mails I read into the mailig list, I switched to
virDomainMemoryPeek.

Using this function keeps up to 14-16 seconds to read 512Mb of memory
with the 64Kb limitation and 2-3 seconds with the 1Mb one; but the
most annoying thing is that I can't run several environment
concurrently as the function keeps failing.
Here's the typical output:

  File "/home/nox/workspace/NOX/src/NOX/hooks.py", line 134, in trigger
    hook.trigger(event)
  File "/home/nox/workspace/NOX/src/NOX/hooks.py", line 33, in trigger
    self.handlers[event]()
  File "/home/nox/workspace/NOX/hooks/volatility.py", line 81, in memory_dump
    for block in Memory(self.ctx):
  File "/home/see/workspace/NOX/src/NOX/lib/libtools.py", line 179, in next
    libvirt.VIR_MEMORY_PHYSICAL)
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 1759, in memoryPeek
    ret = libvirtmod.virDomainMemoryPeek(self._o, start, size, flags)
SystemError: error return without exception set

I can't run more than 3 environments concurrently on a Xeon Quad with
8Gb of memory.

I guess the RPC reply goes in timeout because the system is under
heavy load but I'm not sure as the error output is quite obscure.
Is there any solution to this issue? Is it possible to raise the RPC
reply timeout value so that, even if slowly, I eventually get the
memory dump?

If through virsh I use the QEMU `pmemsave` command, I get the memory
dump in less than one second; is there any way to obtain the same
performance?

Thanks anyway for making libvirt the great tool it is!

NoxDaFox