[ovirt-devel] Memory stats in VDSM

[Juan Hernández]

On 08/28/2017 01:11 PM, Tomáš Golembiovský wrote:
> Hi,
> 
> there is ongoing effort to change how VDSM collects information about
> memory usage from guests. We used to use oVirt guest agent to get the
> statistics about free memory, swap usage, etc. This is going to change
> and we will use stats provided by VirtIO Balloon driver. [1] This should
> not break MOM nor Engine (current or previous versions).
> 
> There is however small downside to this change. We will not be able to
> fetch information about buffers and caches on Linux guests anymore
> (mem_cached and mem_buffers in memoryStats). The corollary of this is
> that free memory reported by Engine will also no longer include those
> statistics and reported free memory will be really (only) free memory.
> 
> I now there will be mixed feelings about this and we would like to get
> the information about buffers and caches back to the VDSM. Correctly via
> balloon driver statistics. [2] This effort will however take some time.
> 
>      Tomas
> 
> 
> [1] https://gerrit.ovirt.org/#/q/topic:memory-stats
> [2] https://lists.nongnu.org/archive/html/qemu-devel/2017-08/msg05239.html
> 

Note that this information is currently reported by the engine REST API, 
so it is part of its contract. Removing it breaks backwards 
compatibility and causes a regression in this RFE:

   [RFE] Report guests Buffered/Cached memory
   https://bugzilla.redhat.com/1024010