Messages in this thread | | | Date | Wed, 30 Jan 2013 18:15:15 +0800 | From | Tang Chen <> | Subject | Re: [PATCH v6 00/15] memory-hotplug: hot-remove physical memory |
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Hi Simon,
Please see below. :)
On 01/29/2013 08:52 PM, Simon Jeons wrote: > Hi Tang, > > On Wed, 2013-01-09 at 17:32 +0800, Tang Chen wrote: >> Here is the physical memory hot-remove patch-set based on 3.8rc-2. > > Some questions ask you, not has relationship with this patchset, but is > memory hotplug stuff. > > 1. In function node_states_check_changes_online: > > comments: > * If we don't have HIGHMEM nor movable node, > * node_states[N_NORMAL_MEMORY] contains nodes which have zones of > * 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE. > > How to understand it? Why we don't have HIGHMEM nor movable node and > node_staes[N_NORMAL_MEMORY] contains 0...ZONE_MOVABLE, IIUC, > N_NORMAL_MEMORY only means the node has regular memory. >
First of all, I think we need to understand why we need N_MEMORY.
In order to support movable node, which has only ZONE_MOVABLE (the last zone), we introduce N_MEMORY to represent the node has normal, highmem and movable memory.
Here, "we have movable node" means you configured CONFIG_MOVABLE_NODE. This config option doesn't mean we don't have movable pages, (NO) it means we don't have a node which has only movable pages (only have ZONE_MOVABLE). (YES)
Here, if we don't have CONFIG_MOVABLE_NODE (we don't have movable node), we don't need a separate node_states[] element to represent a particular node because we won't have a node which has only ZONE_MOVABLE.
So, 1) if we don't have highmem nor movable node, N_MEMORY == N_HIGH_MEMORY == N_NORMAL_MEMORY, which means N_NORMAL_MEMORY effects as N_MEMORY. If we online pages as movable, we need to update node_states[N_NORMAL_MEMORY].
Please refer to the definition of enum zone_type, if we don't have CONFIG_HIGHMEM, we won't have ZONE_HIGHMEM, but ZONE_NORMAL and ZONE_MOVABLE will always there. So we can have movable pages, and the zone_last should be ZONE_MOVABLE.
Again, because we won't have a node only having ZONE_MOVABLE, so we just need to update node_states[N_NORMAL_MEMORY].
> * If we don't have movable node, node_states[N_NORMAL_MEMORY] > * contains nodes which have zones of 0...ZONE_MOVABLE, > * set zone_last to ZONE_MOVABLE. > > How to understand?
2) this code is in #ifdef CONFIG_HIGHMEM, which means we have highmem, so if we don't have movable node, N_MEMORY == N_HIGH_MEMORY, and N_HIGH_MEMORY effects as N_MEMORY. If we online pages as movable, we need to update node_states[N_NORMAL_MEMORY].
> > 2. In function move_pfn_range_left, why end<= z2->zone_start_pfn is not > correct? The comments said that must include/overlap, why? >
This one is easy, if I understand you correctly. move_pfn_range_left() is used to move the left most part [start_pfn, end_pfn) of z2 to z1. So if end_pfn<= z2->zone_start_pfn, it means [start_pfn, end_pfn) is not part of z2. Then it fails.
> 3. In function online_pages, the normal case(w/o online_kenrel, > online_movable), why not check if the new zone is overlap with adjacent > zones? >
Can a zone overlap with the others ? I don't think so.
One pfn could only be in one zone, zone = page_zone(pfn_to_page(pfn));
it could overlap with others, I think. :)
But maybe I misunderstand you. :)
> 4. Could you summarize the difference implementation between hot-add and > logic-add, hot-remove and logic-remove?
Sorry, I don't quite understand what do you mean by logic-add/remove. Would you please explain more ?
If you meant the sys fs interfaces, I think they are just another set of entrances of memory hotplug.
Thanks. :)
> > >> >> This patch-set aims to implement physical memory hot-removing. >> >> The patches can free/remove the following things: >> >> - /sys/firmware/memmap/X/{end, start, type} : [PATCH 4/15] >> - memmap of sparse-vmemmap : [PATCH 6,7,8,10/15] >> - page table of removed memory : [RFC PATCH 7,8,10/15] >> - node and related sysfs files : [RFC PATCH 13-15/15] >> >> >> Existing problem: >> If CONFIG_MEMCG is selected, we will allocate memory to store page cgroup >> when we online pages. >> >> For example: there is a memory device on node 1. The address range >> is [1G, 1.5G). You will find 4 new directories memory8, memory9, memory10, >> and memory11 under the directory /sys/devices/system/memory/. >> >> If CONFIG_MEMCG is selected, when we online memory8, the memory stored page >> cgroup is not provided by this memory device. But when we online memory9, the >> memory stored page cgroup may be provided by memory8. So we can't offline >> memory8 now. We should offline the memory in the reversed order. >> >> When the memory device is hotremoved, we will auto offline memory provided >> by this memory device. But we don't know which memory is onlined first, so >> offlining memory may fail. >> >> In patch1, we provide a solution which is not good enough: >> Iterate twice to offline the memory. >> 1st iterate: offline every non primary memory block. >> 2nd iterate: offline primary (i.e. first added) memory block. >> >> And a new idea from Wen Congyang<wency@cn.fujitsu.com> is: >> allocate the memory from the memory block they are describing. >> >> But we are not sure if it is OK to do so because there is not existing API >> to do so, and we need to move page_cgroup memory allocation from MEM_GOING_ONLINE >> to MEM_ONLINE. And also, it may interfere the hugepage. >> >> >> >> How to test this patchset? >> 1. apply this patchset and build the kernel. MEMORY_HOTPLUG, MEMORY_HOTREMOVE, >> ACPI_HOTPLUG_MEMORY must be selected. >> 2. load the module acpi_memhotplug >> 3. hotplug the memory device(it depends on your hardware) >> You will see the memory device under the directory /sys/bus/acpi/devices/. >> Its name is PNP0C80:XX. >> 4. online/offline pages provided by this memory device >> You can write online/offline to /sys/devices/system/memory/memoryX/state to >> online/offline pages provided by this memory device >> 5. hotremove the memory device >> You can hotremove the memory device by the hardware, or writing 1 to >> /sys/bus/acpi/devices/PNP0C80:XX/eject. > > Is there a similar knode to hot-add the memory device? > >> >> >> Note: if the memory provided by the memory device is used by the kernel, it >> can't be offlined. It is not a bug. >> >> >> Changelogs from v5 to v6: >> Patch3: Add some more comments to explain memory hot-remove. >> Patch4: Remove bootmem member in struct firmware_map_entry. >> Patch6: Repeatedly register bootmem pages when using hugepage. >> Patch8: Repeatedly free bootmem pages when using hugepage. >> Patch14: Don't free pgdat when offlining a node, just reset it to 0. >> Patch15: New patch, pgdat is not freed in patch14, so don't allocate a new >> one when online a node. >> >> Changelogs from v4 to v5: >> Patch7: new patch, move pgdat_resize_lock into sparse_remove_one_section() to >> avoid disabling irq because we need flush tlb when free pagetables. >> Patch8: new patch, pick up some common APIs that are used to free direct mapping >> and vmemmap pagetables. >> Patch9: free direct mapping pagetables on x86_64 arch. >> Patch10: free vmemmap pagetables. >> Patch11: since freeing memmap with vmemmap has been implemented, the config >> macro CONFIG_SPARSEMEM_VMEMMAP when defining __remove_section() is >> no longer needed. >> Patch13: no need to modify acpi_memory_disable_device() since it was removed, >> and add nid parameter when calling remove_memory(). >> >> Changelogs from v3 to v4: >> Patch7: remove unused codes. >> Patch8: fix nr_pages that is passed to free_map_bootmem() >> >> Changelogs from v2 to v3: >> Patch9: call sync_global_pgds() if pgd is changed >> Patch10: fix a problem int the patch >> >> Changelogs from v1 to v2: >> Patch1: new patch, offline memory twice. 1st iterate: offline every non primary >> memory block. 2nd iterate: offline primary (i.e. first added) memory >> block. >> >> Patch3: new patch, no logical change, just remove reduntant codes. >> >> Patch9: merge the patch from wujianguo into this patch. flush tlb on all cpu >> after the pagetable is changed. >> >> Patch12: new patch, free node_data when a node is offlined. >> >> >> Tang Chen (6): >> memory-hotplug: move pgdat_resize_lock into >> sparse_remove_one_section() >> memory-hotplug: remove page table of x86_64 architecture >> memory-hotplug: remove memmap of sparse-vmemmap >> memory-hotplug: Integrated __remove_section() of >> CONFIG_SPARSEMEM_VMEMMAP. >> memory-hotplug: remove sysfs file of node >> memory-hotplug: Do not allocate pdgat if it was not freed when >> offline. >> >> Wen Congyang (5): >> memory-hotplug: try to offline the memory twice to avoid dependence >> memory-hotplug: remove redundant codes >> memory-hotplug: introduce new function arch_remove_memory() for >> removing page table depends on architecture >> memory-hotplug: Common APIs to support page tables hot-remove >> memory-hotplug: free node_data when a node is offlined >> >> Yasuaki Ishimatsu (4): >> memory-hotplug: check whether all memory blocks are offlined or not >> when removing memory >> memory-hotplug: remove /sys/firmware/memmap/X sysfs >> memory-hotplug: implement register_page_bootmem_info_section of >> sparse-vmemmap >> memory-hotplug: memory_hotplug: clear zone when removing the memory >> >> arch/arm64/mm/mmu.c | 3 + >> arch/ia64/mm/discontig.c | 10 + >> arch/ia64/mm/init.c | 18 ++ >> arch/powerpc/mm/init_64.c | 10 + >> arch/powerpc/mm/mem.c | 12 + >> arch/s390/mm/init.c | 12 + >> arch/s390/mm/vmem.c | 10 + >> arch/sh/mm/init.c | 17 ++ >> arch/sparc/mm/init_64.c | 10 + >> arch/tile/mm/init.c | 8 + >> arch/x86/include/asm/pgtable_types.h | 1 + >> arch/x86/mm/init_32.c | 12 + >> arch/x86/mm/init_64.c | 390 +++++++++++++++++++++++++++++ >> arch/x86/mm/pageattr.c | 47 ++-- >> drivers/acpi/acpi_memhotplug.c | 8 +- >> drivers/base/memory.c | 6 + >> drivers/firmware/memmap.c | 96 +++++++- >> include/linux/bootmem.h | 1 + >> include/linux/firmware-map.h | 6 + >> include/linux/memory_hotplug.h | 15 +- >> include/linux/mm.h | 4 +- >> mm/memory_hotplug.c | 459 +++++++++++++++++++++++++++++++--- >> mm/sparse.c | 8 +- >> 23 files changed, 1094 insertions(+), 69 deletions(-) >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email:<a href=mailto:"dont@kvack.org"> email@kvack.org</a> > > >
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