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.
