On Thu 10-09-20 14:49:28, David Hildenbrand wrote: > On 10.09.20 14:47, Michal Hocko wrote: > > On Thu 10-09-20 14:03:48, Oscar Salvador wrote: > >> On Thu, Sep 10, 2020 at 01:35:32PM +0200, Laurent Dufour wrote: > >> > >>> That points has been raised by David, quoting him here: > >>> > >>>> IIRC, ACPI can hotadd memory while SCHEDULING, this patch would break that. > >>>> > >>>> Ccing Oscar, I think he mentioned recently that this is the case with ACPI. > >>> > >>> Oscar told that he need to investigate further on that. > >> > >> I think my reply got lost. > >> > >> We can see acpi hotplugs during SYSTEM_SCHEDULING: > >> > >> $QEMU -enable-kvm -machine pc -smp 4,sockets=4,cores=1,threads=1 -cpu host -monitor pty \ > >> -m size=$MEM,slots=255,maxmem=4294967296k \ > >> -numa node,nodeid=0,cpus=0-3,mem=512 -numa node,nodeid=1,mem=512 \ > >> -object memory-backend-ram,id=memdimm0,size=134217728 -device pc-dimm,node=0,memdev=memdimm0,id=dimm0,slot=0 \ > >> -object memory-backend-ram,id=memdimm1,size=134217728 -device pc-dimm,node=0,memdev=memdimm1,id=dimm1,slot=1 \ > >> -object memory-backend-ram,id=memdimm2,size=134217728 -device pc-dimm,node=0,memdev=memdimm2,id=dimm2,slot=2 \ > >> -object memory-backend-ram,id=memdimm3,size=134217728 -device pc-dimm,node=0,memdev=memdimm3,id=dimm3,slot=3 \ > >> -object memory-backend-ram,id=memdimm4,size=134217728 -device pc-dimm,node=1,memdev=memdimm4,id=dimm4,slot=4 \ > >> -object memory-backend-ram,id=memdimm5,size=134217728 -device pc-dimm,node=1,memdev=memdimm5,id=dimm5,slot=5 \ > >> -object memory-backend-ram,id=memdimm6,size=134217728 -device pc-dimm,node=1,memdev=memdimm6,id=dimm6,slot=6 \ > >> > >> kernel: [ 0.753643] __add_memory: nid: 0 start: 0100000000 - 0108000000 (size: 134217728) > >> kernel: [ 0.756950] register_mem_sect_under_node: system_state= 1 > >> > >> kernel: [ 0.760811] register_mem_sect_under_node+0x4f/0x230 > >> kernel: [ 0.760811] walk_memory_blocks+0x80/0xc0 > >> kernel: [ 0.760811] link_mem_sections+0x32/0x40 > >> kernel: [ 0.760811] add_memory_resource+0x148/0x250 > >> kernel: [ 0.760811] __add_memory+0x5b/0x90 > >> kernel: [ 0.760811] acpi_memory_device_add+0x130/0x300 > >> kernel: [ 0.760811] acpi_bus_attach+0x13c/0x1c0 > >> kernel: [ 0.760811] acpi_bus_attach+0x60/0x1c0 > >> kernel: [ 0.760811] acpi_bus_scan+0x33/0x70 > >> kernel: [ 0.760811] acpi_scan_init+0xea/0x21b > >> kernel: [ 0.760811] acpi_init+0x2f1/0x33c > >> kernel: [ 0.760811] do_one_initcall+0x46/0x1f4 > > > > Is there any actual usecase for a configuration like this? What is the > > point to statically define additional memory like this when the same can > > be achieved on the same command line? > > You can online it movable right away to unplug later. You can use movable_node for that. IIRC this would only all hotplugable memory as movable. > Also, under QEMU, just do a reboot with hotplugged memory and you're in > the very same situation. OK, I didn't know that. I thought the memory would be presented as a normal memory after reboot. Thanks for the clarification. -- Michal Hocko SUSE Labs
