libvirt users - Sep 2013 - virNodeInfo returns MBytes instead of bytes

Hi,

http://www.libvirt.org/html/libvirt-libvirt.html#virNodeInfo says that
memory size is in kilobytes, however when I use this call I get an answer
in Megabytes, see below. The hypervisor has 16 GB of RAM.

$ python
Python 2.6.6 (r266:84292, Jul 10 2013, 22:48:45)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] on linux2
Type "help", "copyright", "credits" or
"license" for more information.
>>> import libvirt
>>> conn=libvirt.open("qemu+ssh://xx@xx.xxx.com/system")
Enter passphrase for key '/home/xx/.ssh/id_rsa':
>>> hv_info=conn.getInfo()
>>> hv_info
['x86_64', 15919, 8, 3292, 1, 1, 4, 2]

15,919 is the number I am referencing, should that not be in bytes and not
MB?
8 is the number of cores, CPU is 3.2Ghz.

$ rpm -q libvirt
libvirt-0.10.2-18.el6_4.14.x86_64

$ uname -a
Linux xx.xxx.com 2.6.32-358.18.1.el6.x86_64 #1 SMP Wed Aug 28 17:19:38 UTC
2013 x86_64 x86_64 x86_64 GNU/Linux

Thanks

On Sun, Sep 29, 2013 at 09:34:07PM -0700, Sam Giraffe
wrote:
> Hi,
> 
> http://www.libvirt.org/html/libvirt-libvirt.html#virNodeInfo says that
> memory size is in kilobytes, however when I use this call I get an answer
> in Megabytes, see below. The hypervisor has 16 GB of RAM.
> 
> $ python
> Python 2.6.6 (r266:84292, Jul 10 2013, 22:48:45)
> [GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] on linux2
> Type "help", "copyright", "credits" or
"license" for more information.
> 
> >>> import libvirt
> 
> >>> conn=libvirt.open("qemu+ssh://xx@xx.xxx.com/system")
> Enter passphrase for key '/home/xx/.ssh/id_rsa':
> 
> >>> hv_info=conn.getInfo()
> 
> >>> hv_info
> ['x86_64', 15919, 8, 3292, 1, 1, 4, 2]
> 
> 15,919 is the number I am referencing, should that not be in bytes and not
> MB?
God knows why this was done, but the python binding was written to convert
the KB value from the C API into MB :-(

    PyList_SetItem(py_retval, 1, libvirt_longWrap((long) info.memory >>
10));

For backwards compat reasons, we cannot change that default behaviour:-)

We could I guess add a flag to let you request sane behaviour though
eg something like

    conn.getInfo(memkb=True)

Daniel
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On 30.09.2013 06:34, Sam Giraffe wrote:
> Hi,
> 
> http://www.libvirt.org/html/libvirt-libvirt.html#virNodeInfo says that
> memory size is in kilobytes, however when I use this call I get an
> answer in Megabytes, see below. The hypervisor has 16 GB of RAM.
> 
> $ python
> Python 2.6.6 (r266:84292, Jul 10 2013, 22:48:45)
> [GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] on linux2
> Type "help", "copyright", "credits" or
"license" for more information.
> 
>>>> import libvirt
> 
>>>> conn=libvirt.open("qemu+ssh://xx@xx.xxx.com/system
> <http://xx@xx.xxx.com/system>")
> Enter passphrase for key '/home/xx/.ssh/id_rsa':
> 
>>>> hv_info=conn.getInfo()
> 
>>>> hv_info
> ['x86_64', 15919, 8, 3292, 1, 1, 4, 2]
This is the python bindings bug. From the code:

http://libvirt.org/git/?p=libvirt.git;a=blob;f=python/libvirt-override.c;h=e659bae30ad01b315041e29913fb442c348ed0f6;hb=HEAD#l2846

We are shifting the mem amount left 10 times (effectively divide it by
1024). Hence you'll get MB instead of KB. Although I am not quite sure
how to fix this. I see two options:

1) fix the code (possibly breaking other applications already relying on
the bug)

2) document it as known bug (not consistent with C struct)

Michal