Hi Ly, So basically just to be clear, indeed memory_over_commit is the solution for memory over commitment. Changing it enabled you to run the amount of VMs you need.
----- Original Message ----- > From: "ly pan" <ply...@gmail.com> > To: "Doron Fediuck" <dfedi...@redhat.com> > Cc: engine-devel@ovirt.org > Sent: Wednesday, October 31, 2012 12:32:48 PM > Subject: Re: [Engine-devel] Question about hasMemoryToRunVM() in > RunVmCommandBase > > Hi Doron, > > Sorry for the so late reply. > These days I looked into the code again and found it's my setting not > rightly configured. > 1. You opinion about reserved_mem is right. > 2. Yes, pending_vmem_size is 0 before the 84th runs. > 3. memory_over_commit is where my problem is. > > In webadmin UI, I set the cluster's memory optimization > to none, thus memory_over_commit is 100 in DB(the dafault value is > 100 > in my env). > when I set the cluster's mem_opt to 'for server load', > memory_over_commit grows to 150 > and when I set to 'for desktop load', memory_over_commit grows to > 200. > > Both 'for server load' and 'for desktop load' have let the > vdsMemLimit > grows dramaticaly, > thus the 84th vm managed to run. > So I realized the memory optimization option in cluster is for KSM > function. > > Thank you. > > ly pan > > > 2012/10/24 Doron Fediuck <dfedi...@redhat.com>: > > ----- Original Message ----- > >> From: "ly pan" <ply...@gmail.com> > >> To: engine-devel@ovirt.org > >> Sent: Thursday, October 18, 2012 2:43:35 PM > >> Subject: [Engine-devel] Question about hasMemoryToRunVM() in > >> RunVmCommandBase > >> > >> Hi: > >> > >> This is my test environment: > >> hardware: Dell PowerEdge 2710 ,Memory 48G > >> Software: OVirt engine 3.0 ,VDSM 4.9.4 ,kernel > >> 2.6.32-279.2.1.el6.x86_64 > >> > >> > >> I create 100 vms from pool(each vm has 512M memory and has > >> 1M memory garanteed, with guest_overhead = 65 and reserved_mem = > >> 256), > >> but only 83 vms > >> turn out to run. When I run the 84th vm, engine says there is not > >> enough memory. However at this time KSM is enabled and 15G free > >> memory > >> is still left on the host. > >> > >> I checked the code and found out that before running a vm, the > >> function hasMemoryToRunVM() in RunVmCommandBase would decide > >> whether > >> there is enough memory in the selected host to run it. > >> The Algorithm in the function is like this: > >> mem_avaliable >= mem_required = curVds.getmem_commited() + > >> curVds.getpending_vmem_size() > >> + curVds.getguest_overhead() + curVds.getreserved_mem() + > >> vm.getMinAllocatedMem(); > >> > >> And here is my question: curVds.getmem_commited() is caculated > >> from > >> the memory of vm > >> assigned by user. But when the host is running with KSM enabled, > >> the > >> actual memory of each > >> running vm would be smaller than the memory the user assigned to. > >> In > >> this case, the following > >> may occur: engine says there be no more memroy to run any vm while > >> the > >> host has much free > >> space to run more vms(in my case, 15G). > >> > >> > >> Therefore I think the actual memory size reported by vdsm(The KSM > >> shared memory) should be taken into account when calculating > >> curVds.getmem_commited(). Any ideas are welcome. > > > > Hi Ly, > > Sorry for the delay. I'd like to look into this issue. > > In the meanwhile a few relevant points; > > > > 1. You're saying that reserved_mem=256. This is not accurate, since > > it's > > reported by vds as host_mem_reserve(256) + extra_mem_reserve(65) = > > 321 > > > > 2. I'm assuming you retried running the 84th vm, just to make sure > > your > > pending_vmem_size is 0 once all 83 VMs are running. > > > > 3. So assuming (2) is correct, I'd like to ask what's the > > max_vds_memory_over_commit > > you have for the cluster? By default it's set to 120, and in such a > > case the 84th > > VM should still be running. > > > > Here's a calculation sample based on your data, and the above 3 > > issues: > > > > vdsCurrentMem = > > 83 * (512M+65) = 47,891 > > 0 > > 65 > > 321 > > 1 > > ======= > > 48,278 > > > > vdsMemLimit = > > 120/100 > > * > > 47,321.1328125 // reported by vdsm: 'cat /proc/meminfo | grep > > MemTotal' / 1024 > > ========= > > 56,785.359375 > > > > So vdsCurrentMem <= vdsMemLimit should be true unless you changed > > something > > such as the MemTotal or the memory_over_commit. You can try and > > change memory_over_commit > > let us know how it works. > > > > Doron > _______________________________________________ > Engine-devel mailing list > Engine-devel@ovirt.org > http://lists.ovirt.org/mailman/listinfo/engine-devel > _______________________________________________ Engine-devel mailing list Engine-devel@ovirt.org http://lists.ovirt.org/mailman/listinfo/engine-devel
