On 15.02.22 10:48, Ani Sinha wrote: > On Tue, Feb 15, 2022 at 3:14 PM David Hildenbrand <da...@redhat.com> wrote: >> >> On 15.02.22 10:40, Ani Sinha wrote: >>> On Tue, Feb 15, 2022 at 2:08 PM David Hildenbrand <da...@redhat.com> wrote: >>>> >>>> On 15.02.22 09:12, Ani Sinha wrote: >>>>> On Tue, Feb 15, 2022 at 1:25 PM David Hildenbrand <da...@redhat.com> >>>>> wrote: >>>>>> >>>>>> On 15.02.22 08:00, Ani Sinha wrote: >>>>>>> >>>>>>> >>>>>>> On Mon, 14 Feb 2022, David Hildenbrand wrote: >>>>>>> >>>>>>>> On 14.02.22 13:36, Igor Mammedov wrote: >>>>>>>>> On Mon, 14 Feb 2022 10:54:22 +0530 (IST) >>>>>>>>> Ani Sinha <a...@anisinha.ca> wrote: >>>>>>>>> >>>>>>>>>> Hi Igor: >>>>>>>>>> >>>>>>>>>> I failed to spawn a 9 Tib VM. The max I could do was a 2 TiB vm on my >>>>>>>>>> system with the following commandline before either the system >>>>>>>>>> destabilized or the OOM killed killed qemu >>>>>>>>>> >>>>>>>>>> -m 2T,maxmem=9T,slots=1 \ >>>>>>>>>> -object >>>>>>>>>> memory-backend-file,id=mem0,size=2T,mem-path=/data/temp/memfile,prealloc=off >>>>>>>>>> \ >>>>>>>>>> -machine memory-backend=mem0 \ >>>>>>>>>> -chardev file,path=/tmp/debugcon2.txt,id=debugcon \ >>>>>>>>>> -device isa-debugcon,iobase=0x402,chardev=debugcon \ >>>>>>>>>> >>>>>>>>>> I have attached the debugcon output from 2 TiB vm. >>>>>>>>>> Is there any other commandline parameters or options I should try? >>>>>>>>>> >>>>>>>>>> thanks >>>>>>>>>> ani >>>>>>>>> >>>>>>>>> $ truncate -s 9T 9tb_sparse_disk.img >>>>>>>>> $ qemu-system-x86_64 -m 9T \ >>>>>>>>> -object >>>>>>>>> memory-backend-file,id=mem0,size=9T,mem-path=9tb_sparse_disk.img,prealloc=off,share=on >>>>>>>>> \ >>>>>>>>> -machine memory-backend=mem0 >>>>>>>>> >>>>>>>>> works for me till GRUB menu, with sufficient guest kernel >>>>>>>>> persuasion (i.e. CLI limit ram size to something reasonable) you can >>>>>>>>> boot linux >>>>>>>>> guest on it and inspect SMBIOS tables comfortably. >>>>>>>>> >>>>>>>>> >>>>>>>>> With KVM enabled it bails out with: >>>>>>>>> qemu-system-x86_64: kvm_set_user_memory_region: >>>>>>>>> KVM_SET_USER_MEMORY_REGION failed, slot=1, start=0x100000000, >>>>>>>>> size=0x8ff40000000: Invalid argument >>>>>>>>> >>>>>>> >>>>>>> I have seen this in my system but not always. Maybe I should have dug >>>>>>> deeper as to why i do see this all the time. >>>>>>> >>>>>>>>> all of that on a host with 32G of RAM/no swap. >>>>>>>>> >>>>>>> >>>>>>> My system in 16 Gib of main memory, no swap. >>>>>>> >>>>>>>> >>>>>>>> #define KVM_MEM_MAX_NR_PAGES ((1UL << 31) - 1) >>>>>>>> >>>>>>>> ~8 TiB (7,999999) >>>>>>> >>>>>>> That's not 8 Tib, thats 2 GiB. But yes, 0x8ff40000000 is certainly >>>>>>> greater >>>>>>> than 2 Gib * 4K (assuming 4K size pages). >>>>>> >>>>>> "pages" don't carry the unit "GiB/TiB", so I was talking about the >>>>>> actual size with 4k pages (your setup, I assume) >>>>> >>>>> yes I got that after reading your email again. >>>>> The interesting question now is how is redhat QE running 9 TiB vm with >>>>> kvm? >>>> >>>> As already indicated by me regarding s390x only having single large NUMA >>>> nodes, x86 is usually using multiple NUMA nodes with such large memory. >>>> And QE seems to be using virtual numa nodes: >>>> >>>> Each of the 32 virtual numa nodes receive a: >>>> >>>> -object memory-backend-ram,id=ram-node20,size=309237645312,host- >>>> nodes=0-31,policy=bind >>>> >>>> which results in a dedicated KVM memslot (just like each DIMM would) >>>> >>>> >>>> 32 * 309237645312 == 9 TiB :) >>> >>> ah, I should have looked closely at the other commandlines before >>> shooting off the email. Yes the limitation is per mem-slot and they >>> have 32 slots one per node. >>> ok so should we do >>> kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES); >>> from i386 kvm_arch_init()? >> >> >> As I said, I'm not a friend of these workarounds in user space. > > Oh ok, did not realize you were against s390x like workarounds. >
s390x doesn't support DIMMs so it was "easy" for them to just do it that way :) -- Thanks, David / dhildenb
