Re: [ovirt-devel] Memory stats in VDSM

On 08/28/2017 01:42 PM, Michal Skrivanek wrote: > >> On 28 Aug 2017, at 13:37, Juan Hernández <jhernand(a)redhat.com&gt; wrote: >> >> 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: > > we can either declare it deprecated or temporarily report 0 until the > support propagates into qemu-ga > So there will be an interval of time where it will not be reported? Will that affect released versions of the system or it is just something that we will re-add before the next release? It is released versions of the system that I am concerned about. We should not do a release that breaks backwards compatibility. It is completely OK if we break it in between releases. > I think best way forward is to just make it optionally available when > ovirt-guest-agent reports it. > I.e. users will get only part of the information when they run only > qemu-ga, and that’s fine… >

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