On Mon 13-03-17 14:57:12, Igor Mammedov wrote: > On Mon, 13 Mar 2017 11:43:02 +0100 > Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > On Mon 13-03-17 11:31:10, Igor Mammedov wrote: > > > On Fri, 10 Mar 2017 14:58:07 +0100 > > [...] > > > > [ 0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x00000000-0x0009ffff] > > > > [ 0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x00100000-0x3fffffff] > > > > [ 0.000000] ACPI: SRAT: Node 1 PXM 1 [mem 0x40000000-0x7fffffff] > > > > [ 0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x100000000-0x27fffffff] hotplug > > > > [ 0.000000] NUMA: Node 0 [mem 0x00000000-0x0009ffff] + [mem 0x00100000-0x3fffffff] -> [mem 0x00000000-0x3fffffff] > > > > [ 0.000000] NODE_DATA(0) allocated [mem 0x3fffc000-0x3fffffff] > > > > [ 0.000000] NODE_DATA(1) allocated [mem 0x7ffdc000-0x7ffdffff] > > > > [ 0.000000] Zone ranges: > > > > [ 0.000000] DMA [mem 0x0000000000001000-0x0000000000ffffff] > > > > [ 0.000000] DMA32 [mem 0x0000000001000000-0x000000007ffdffff] > > > > [ 0.000000] Normal empty > > > > [ 0.000000] Movable zone start for each node > > > > [ 0.000000] Early memory node ranges > > > > [ 0.000000] node 0: [mem 0x0000000000001000-0x000000000009efff] > > > > [ 0.000000] node 0: [mem 0x0000000000100000-0x000000003fffffff] > > > > [ 0.000000] node 1: [mem 0x0000000040000000-0x000000007ffdffff] > > > > > > > > so there is neither any normal zone nor movable one at the boot time. > > > it could be if hotpluggable memory were present at boot time in E802 table > > > (if I remember right when running on hyperv there is movable zone at boot time), > > > > > > but in qemu hotpluggable memory isn't put into E820, > > > so zone is allocated later when memory is enumerated > > > by ACPI subsystem and onlined. > > > It causes less issues wrt movable zone and works for > > > different versions of linux/windows as well. > > > > > > That's where in kernel auto-onlining could be also useful, > > > since user would be able to start-up with with small > > > non removable memory plus several removable DIMMs > > > and have all the memory onlined/available by the time > > > initrd is loaded. (missing piece here is onling > > > removable memory as movable by default). > > > > Why we should even care to online that memory that early rather than > > making it available via e820? > > It's not forbidden by spec and has less complications > when it comes to removable memory. Declaring it in E820 > would add following limitations/drawbacks: > - firmware should be able to exclude removable memory > from its usage (currently SeaBIOS nor EFI have to > know/care about it) => less qemu-guest ABI to maintain. > - OS should be taught to avoid/move (early) nonmovable > allocations from removable address ranges. > There were patches targeting that in recent kernels, > but it won't work with older kernels that don't have it. > So limiting a range of OSes that could run on QEMU > and do memory removal. > > E820 less approach works reasonably well with wide range > of guest OSes and less complex that if removable memory > were present it E820. Hence I don't have a compelling > reason to introduce removable memory in E820 as it > only adds to hot(un)plug issues. OK I see and that sounds like an argument to not put those ranges to E820. I still fail to see why we haeve to online the memory early during the boot and cannot wait for userspace to run? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
