Hello, Are you sure that those are the exact values for the host? OpenNebula counts "real" (from probes) and allocated (from database) memory so that should not happen.
Snippet from a onehost show: --8<------ USED MEM (REAL) : 0 USED MEM (ALLOCATED) : 65536 ------>8-- I am now working on the kvm monitoring and I have noticed another mismatch even with your probe changes. The values stored in the database for total memory should be changed and that's what I am working on. I am connected to irc.freenode.org in channel #opennebula if you want to discuss this further. Bye On Thu, Nov 11, 2010 at 5:20 AM, Shashank Rachamalla <[email protected]> wrote: > Hi Javier > > Thanks for the inputs but I came across another problem while testing: > > If opennebula receives multiple vm requests in a short span of time, the > scheduler might take decisions for all these vms considering the host > monitoring information available from the last monitoring cycle. Ideally, > before processing every pending request, fresh host monitoring information > has to be taken into account as the previous set of requests might have > already changed the host’s state. This can result in over committing when > host is being used close to its full capacity. > > Is there any workaround which helps the scheduler to overcome the above > problem ? > > steps to reproduce the problem scenario: > > Host 1 : Total memory = 3GB > Host 2 : Total memory = 2GB > Assume Host1 and Host2 have same number of CPU cores. ( Host1 will have a > higher RANK value ) > > VM1: memory = 2GB > VM2: memroy = 2GB > > Start VM1 and VM2 immediately one after the other. Both VM1 and VM2 will > come up on Host1. ( Thus over committing ) > > Start VM1 and VM2 with an intermediate delay of 60sec. VM1 will come up on > Host1 and VM2 will come up on Host2. This is true because opennebula would > have fetched a fresh set of host monitoring information in that time. > > > On 4 November 2010 02:04, Javier Fontan <[email protected]> wrote: >> >> Hello, >> >> It looks fine to me. I think that taking out the memory the hypervisor >> may be consuming is key to make it work. >> >> Bye >> >> On Wed, Nov 3, 2010 at 8:32 PM, Rangababu Chakravarthula >> <[email protected]> wrote: >> > Javier >> > >> > Yes we are using KVM and OpenNebula 1.4. >> > >> > We have been having this problem since a long time and we were doing all >> > kinds of validations ourselves before submitting the request to >> > OpenNebula. >> > (there should be enough memory in the cloud that matches the requested >> > memory & there should be atleast one host that has memory > requested >> > memory >> > ) We had to do those because OpenNebula would schedule to an arbitrary >> > host based on the existing logic it had. >> > So at last we thought that we need to make OpenNebula aware of memory >> > allocated of running VM's on the host and started this discussion. >> > >> > Thanks for taking up this issue as priority. Appreciate it. >> > >> > Shashank came up with this patch to kvm.rb. Please take a look and let >> > us >> > know if that will work until we get a permanent solution. >> > >> > >> > ==================================================================================== >> > >> > $mem_allocated_for_running_vms=0 >> > for i in `virsh list|grep running|tr -s ' ' ' '|cut -f2 -d' '` do >> > $dominfo=`virsh dominfo #{i}` >> > $dominfo.split(/\n/).each{|line| >> > if line.match('^Max memory') >> > $mem_allocated_for_running_vms += line.split(" >> > ")[2].strip.to_i >> > end >> > } >> > end >> > >> > $mem_used_by_base_hypervisor = [some xyz kb that we want to set aside >> > for >> > hypervisor] >> > >> > $free_memory = $total_memory.to_i - ( >> > $mem_allocated_for_running_vms.to_i + >> > $mem_used_by_base_hypervisor.to_i ) >> > >> > >> > ====================================================================================== >> > >> > Ranga >> > >> > On Wed, Nov 3, 2010 at 2:16 PM, Javier Fontan <[email protected]> wrote: >> >> >> >> Hello, >> >> >> >> Sorry for the delay in the response. >> >> >> >> It looks that the problem is OpenNebula calculating available memory. >> >> For xen >= 3.2 there is a reliable way to get available memory that is >> >> calling "xm info" and getting "max_free_memory" attribute. >> >> Unfortunately for kvm or xen < 3.2 there is not such attribute. I >> >> suppose you are using kvm as you tell about "free" command. >> >> >> >> I began analyzing the kvm IM probe that gets memory information and >> >> there is a problem on the way to get total memory. Here is how it now >> >> gets memory information: >> >> >> >> TOTALMEMORY: runs virsh info that gets the real physical memory >> >> installed in the machine >> >> FREEMEMORY: runs free command and gets the free column data without >> >> buffers and cache >> >> USEDMEMORY: runs top command and gets used memory from it (this counts >> >> buffers and cache) >> >> >> >> This is a big problem as those values do not match one with another (I >> >> don't really know how I failed to see this before). Here is the >> >> monitoring data from a host without VMs. >> >> >> >> --8<------ >> >> TOTALMEMORY=8193988 >> >> USEDMEMORY=7819952 >> >> FREEMEMORY=7911924 >> >> ------>8-- >> >> >> >> As you can see it makes no sense at all. Even the TOTALMEMORY that is >> >> got from virsh info is very misleading for oned as the host linux >> >> instance does not have access to all that memory (some is consumed by >> >> the hypervisor itself) as seen calling a free command: >> >> >> >> --8<------ >> >> total used free shared buffers >> >> cached >> >> Mem: 8193988 7819192 374796 0 64176 >> >> 7473992 >> >> ------>8-- >> >> >> >> I am also copying this text as an issue to solve this problem >> >> http://dev.opennebula.org/issues/388. It is masked to be solved for >> >> 2.0.1 but the change will be compatible with 1.4 as it seems the the >> >> only changed needed is the IM problem. >> >> >> >> I can not offer you an immediate solution but we'll try to come up >> >> with one as soon as possible. >> >> >> >> Bye >> >> >> >> On Wed, Nov 3, 2010 at 7:08 PM, Rangababu Chakravarthula >> >> <[email protected]> wrote: >> >> > Hello Javier >> >> > Please let us know if you want us to provide more detailed >> >> > information >> >> > with >> >> > examples? >> >> > >> >> > Ranga >> >> > >> >> > On Fri, Oct 29, 2010 at 9:46 AM, Rangababu Chakravarthula >> >> > <[email protected]> wrote: >> >> >> >> >> >> Javier >> >> >> >> >> >> We saw that VM's were being deployed to the host where the allocated >> >> >> memory of all the VM's was higher than the available memory on the >> >> >> host. >> >> >> >> >> >> We think OpenNebula is executing free command on the host to >> >> >> determine >> >> >> if >> >> >> there is any room and since free would always return the actual >> >> >> memory >> >> >> that >> >> >> is being consumed and not the allocated, opennebula would push the >> >> >> new >> >> >> jobs >> >> >> to the host. >> >> >> >> >> >> That's the reason we want OpenNebula to be aware of memory allocated >> >> >> to >> >> >> the VM's on the host. >> >> >> >> >> >> Ranga >> >> >> >> >> >> On Thu, Oct 28, 2010 at 2:02 PM, Javier Fontan <[email protected]> >> >> >> wrote: >> >> >>> >> >> >>> Hello, >> >> >>> >> >> >>> Could you describe the problem you had? By default the scheduler >> >> >>> will >> >> >>> not overcommit cpu nor memory. >> >> >>> >> >> >>> Bye >> >> >>> >> >> >>> On Thu, Oct 28, 2010 at 4:50 AM, Shashank Rachamalla >> >> >>> <[email protected]> wrote: >> >> >>> > Hi >> >> >>> > >> >> >>> > We have a requirement where in the scheduler should not allow >> >> >>> > memory >> >> >>> > over >> >> >>> > committing while choosing a host for new vm. In order to achieve >> >> >>> > this, >> >> >>> > we >> >> >>> > have changed the way in which FREEMEMORY is being calculated for >> >> >>> > each >> >> >>> > host: >> >> >>> > >> >> >>> > FREE MEMORY = TOTAL MEMORY - [ Sum of memory values allocated to >> >> >>> > VMs >> >> >>> > which >> >> >>> > are currently running on the host ] >> >> >>> > >> >> >>> > Please let us know if the above approach is fine or is there any >> >> >>> > better >> >> >>> > way >> >> >>> > to accomplish the task. We are using opennebula 1.4. >> >> >>> > >> >> >>> > -- >> >> >>> > Regards, >> >> >>> > Shashank Rachamalla >> >> >>> > >> >> >>> > _______________________________________________ >> >> >>> > Users mailing list >> >> >>> > [email protected] >> >> >>> > http://lists.opennebula.org/listinfo.cgi/users-opennebula.org >> >> >>> > >> >> >>> > >> >> >>> >> >> >>> >> >> >>> >> >> >>> -- >> >> >>> Javier Fontan, Grid & Virtualization Technology Engineer/Researcher >> >> >>> DSA Research Group: http://dsa-research.org >> >> >>> Globus GridWay Metascheduler: http://www.GridWay.org >> >> >>> OpenNebula Virtual Infrastructure Engine: http://www.OpenNebula.org >> >> >>> _______________________________________________ >> >> >>> Users mailing list >> >> >>> [email protected] >> >> >>> http://lists.opennebula.org/listinfo.cgi/users-opennebula.org >> >> >> >> >> > >> >> > >> >> >> >> >> >> >> >> -- >> >> Javier Fontan, Grid & Virtualization Technology Engineer/Researcher >> >> DSA Research Group: http://dsa-research.org >> >> Globus GridWay Metascheduler: http://www.GridWay.org >> >> OpenNebula Virtual Infrastructure Engine: http://www.OpenNebula.org >> > >> > >> >> >> >> -- >> Javier Fontan, Grid & Virtualization Technology Engineer/Researcher >> DSA Research Group: http://dsa-research.org >> Globus GridWay Metascheduler: http://www.GridWay.org >> OpenNebula Virtual Infrastructure Engine: http://www.OpenNebula.org > > > > -- > Regards, > Shashank Rachamalla > -- Javier Fontan, Grid & Virtualization Technology Engineer/Researcher DSA Research Group: http://dsa-research.org Globus GridWay Metascheduler: http://www.GridWay.org OpenNebula Virtual Infrastructure Engine: http://www.OpenNebula.org _______________________________________________ Users mailing list [email protected] http://lists.opennebula.org/listinfo.cgi/users-opennebula.org
