- 16 Oct, 2020 40 commits
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David Hildenbrand authored
__free_pages_core() is used when exposing fresh memory to the buddy during system boot and when onlining memory in generic_online_page(). generic_online_page() is used in two cases: 1. Direct memory onlining in online_pages(). 2. Deferred memory onlining in memory-ballooning-like mechanisms (HyperV balloon and virtio-mem), when parts of a section are kept fake-offline to be fake-onlined later on. In 1, we already place pages to the tail of the freelist. Pages will be freed to MIGRATE_ISOLATE lists first and moved to the tail of the freelists via undo_isolate_page_range(). In 2, we currently don't implement a proper rule. In case of virtio-mem, where we currently always online MAX_ORDER - 1 pages, the pages will be placed to the HEAD of the freelist - undesireable. While the hyper-v balloon calls generic_online_page() with single pages, usually it will call it on successive single pages in a larger block. The pages are fresh, so place them to the tail of the freelist and avoid the PCP. In __free_pages_core(), remove the now superflouos call to set_page_refcounted() and add a comment regarding page initialization and the refcount. Note: In 2. we currently don't shuffle. If ever relevant (page shuffling is usually of limited use in virtualized environments), we might want to shuffle after a sequence of generic_online_page() calls in the relevant callers. Signed-off-by:
David Hildenbrand <david@redhat.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Reviewed-by:
Vlastimil Babka <vbabka@suse.cz> Reviewed-by:
Oscar Salvador <osalvador@suse.de> Reviewed-by:
Wei Yang <richard.weiyang@linux.alibaba.com> Acked-by:
Pankaj Gupta <pankaj.gupta.linux@gmail.com> Acked-by:
Michal Hocko <mhocko@suse.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Wei Liu <wei.liu@kernel.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@kernel.org> Cc: Scott Cheloha <cheloha@linux.ibm.com> Link: https://lkml.kernel.org/r/20201005121534.15649-5-david@redhat.comSigned-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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David Hildenbrand authored
Whenever we move pages between freelists via move_to_free_list()/ move_freepages_block(), we don't actually touch the pages: 1. Page isolation doesn't actually touch the pages, it simply isolates pageblocks and moves all free pages to the MIGRATE_ISOLATE freelist. When undoing isolation, we move the pages back to the target list. 2. Page stealing (steal_suitable_fallback()) moves free pages directly between lists without touching them. 3. reserve_highatomic_pageblock()/unreserve_highatomic_pageblock() moves free pages directly between freelists without touching them. We already place pages to the tail of the freelists when undoing isolation via __putback_isolated_page(), let's do it in any case (e.g., if order <= pageblock_order) and document the behavior. To simplify, let's move the pages to the tail for all move_to_free_list()/move_freepages_block() users. In 2., the target list is empty, so there should be no change. In 3., we might observe a change, however, highatomic is more concerned about allocations succeeding than cache hotness - if we ever realize this change degrades a workload, we can special-case this instance and add a proper comment. This change results in all pages getting onlined via online_pages() to be placed to the tail of the freelist. Signed-off-by:
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David Hildenbrand authored
__putback_isolated_page() already documents that pages will be placed to the tail of the freelist - this is, however, not the case for "order >= MAX_ORDER - 2" (see buddy_merge_likely()) - which should be the case for all existing users. This change affects two users: - free page reporting - page isolation, when undoing the isolation (including memory onlining). This behavior is desirable for pages that haven't really been touched lately, so exactly the two users that don't actually read/write page content, but rather move untouched pages. The new behavior is especially desirable for memory onlining, where we allow allocation of newly onlined pages via undo_isolate_page_range() in online_pages(). Right now, we always place them to the head of the freelist, resulting in undesireable behavior: Assume we add individual memory chunks via add_memory() and online them right away to the NORMAL zone. We create a dependency chain of unmovable allocations e.g., via the memmap. The memmap of the next chunk will be placed onto previous chunks - if the last block cannot get offlined+removed, all dependent ones cannot get offlined+removed. While this can already be observed with individual DIMMs, it's more of an issue for virtio-mem (and I suspect also ppc DLPAR). Document that this should only be used for optimizations, and no code should rely on this behavior for correction (if the order of the freelists ever changes). We won't care about page shuffling: memory onlining already properly shuffles after onlining. free page reporting doesn't care about physically contiguous ranges, and there are already cases where page isolation will simply move (physically close) free pages to (currently) the head of the freelists via move_freepages_block() instead of shuffling. If this becomes ever relevant, we should shuffle the whole zone when undoing isolation of larger ranges, and after free_contig_range(). Signed-off-by:
Alexander Duyck <alexander.h.duyck@linux.intel.com> Reviewed-by:
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David Hildenbrand authored
Patch series "mm: place pages to the freelist tail when onlining and undoing isolation", v2. When adding separate memory blocks via add_memory*() and onlining them immediately, the metadata (especially the memmap) of the next block will be placed onto one of the just added+onlined block. This creates a chain of unmovable allocations: If the last memory block cannot get offlined+removed() so will all dependent ones. We directly have unmovable allocations all over the place. This can be observed quite easily using virtio-mem, however, it can also be observed when using DIMMs. The freshly onlined pages will usually be placed to the head of the freelists, meaning they will be allocated next, turning the just-added memory usually immediately un-removable. The fresh pages are cold, prefering to allocate others (that might be hot) also feels to be the natural thing to do. It also applies to the hyper-v balloon xen-balloon, and ppc64 dlpar: when adding separate, successive memory blocks, each memory block will have unmovable allocations on them - for example gigantic pages will fail to allocate. While the ZONE_NORMAL doesn't provide any guarantees that memory can get offlined+removed again (any kind of fragmentation with unmovable allocations is possible), there are many scenarios (hotplugging a lot of memory, running workload, hotunplug some memory/as much as possible) where we can offline+remove quite a lot with this patchset. a) To visualize the problem, a very simple example: Start a VM with 4GB and 8GB of virtio-mem memory: [root@localhost ~]# lsmem RANGE SIZE STATE REMOVABLE BLOCK 0x0000000000000000-0x00000000bfffffff 3G online yes 0-23 0x0000000100000000-0x000000033fffffff 9G online yes 32-103 Memory block size: 128M Total online memory: 12G Total offline memory: 0B Then try to unplug as much as possible using virtio-mem. Observe which memory blocks are still around. Without this patch set: [root@localhost ~]# lsmem RANGE SIZE STATE REMOVABLE BLOCK 0x0000000000000000-0x00000000bfffffff 3G online yes 0-23 0x0000000100000000-0x000000013fffffff 1G online yes 32-39 0x0000000148000000-0x000000014fffffff 128M online yes 41 0x0000000158000000-0x000000015fffffff 128M online yes 43 0x0000000168000000-0x000000016fffffff 128M online yes 45 0x0000000178000000-0x000000017fffffff 128M online yes 47 0x0000000188000000-0x0000000197ffffff 256M online yes 49-50 0x00000001a0000000-0x00000001a7ffffff 128M online yes 52 0x00000001b0000000-0x00000001b7ffffff 128M online yes 54 0x00000001c0000000-0x00000001c7ffffff 128M online yes 56 0x00000001d0000000-0x00000001d7ffffff 128M online yes 58 0x00000001e0000000-0x00000001e7ffffff 128M online yes 60 0x00000001f0000000-0x00000001f7ffffff 128M online yes 62 0x0000000200000000-0x0000000207ffffff 128M online yes 64 0x0000000210000000-0x0000000217ffffff 128M online yes 66 0x0000000220000000-0x0000000227ffffff 128M online yes 68 0x0000000230000000-0x0000000237ffffff 128M online yes 70 0x0000000240000000-0x0000000247ffffff 128M online yes 72 0x0000000250000000-0x0000000257ffffff 128M online yes 74 0x0000000260000000-0x0000000267ffffff 128M online yes 76 0x0000000270000000-0x0000000277ffffff 128M online yes 78 0x0000000280000000-0x0000000287ffffff 128M online yes 80 0x0000000290000000-0x0000000297ffffff 128M online yes 82 0x00000002a0000000-0x00000002a7ffffff 128M online yes 84 0x00000002b0000000-0x00000002b7ffffff 128M online yes 86 0x00000002c0000000-0x00000002c7ffffff 128M online yes 88 0x00000002d0000000-0x00000002d7ffffff 128M online yes 90 0x00000002e0000000-0x00000002e7ffffff 128M online yes 92 0x00000002f0000000-0x00000002f7ffffff 128M online yes 94 0x0000000300000000-0x0000000307ffffff 128M online yes 96 0x0000000310000000-0x0000000317ffffff 128M online yes 98 0x0000000320000000-0x0000000327ffffff 128M online yes 100 0x0000000330000000-0x000000033fffffff 256M online yes 102-103 Memory block size: 128M Total online memory: 8.1G Total offline memory: 0B With this patch set: [root@localhost ~]# lsmem RANGE SIZE STATE REMOVABLE BLOCK 0x0000000000000000-0x00000000bfffffff 3G online yes 0-23 0x0000000100000000-0x000000013fffffff 1G online yes 32-39 Memory block size: 128M Total online memory: 4G Total offline memory: 0B All memory can get unplugged, all memory block can get removed. Of course, no workload ran and the system was basically idle, but it highlights the issue - the fairly deterministic chain of unmovable allocations. When a huge page for the 2MB memmap is needed, a just-onlined 4MB page will be split. The remaining 2MB page will be used for the memmap of the next memory block. So one memory block will hold the memmap of the two following memory blocks. Finally the pages of the last-onlined memory block will get used for the next bigger allocations - if any allocation is unmovable, all dependent memory blocks cannot get unplugged and removed until that allocation is gone. Note that with bigger memory blocks (e.g., 256MB), *all* memory blocks are dependent and none can get unplugged again! b) Experiment with memory intensive workload I performed an experiment with an older version of this patch set (before we used undo_isolate_page_range() in online_pages(): Hotplug 56GB to a VM with an initial 4GB, onlining all memory to ZONE_NORMAL right from the kernel when adding it. I then run various memory intensive workloads that consume most system memory for a total of 45 minutes. Once finished, I try to unplug as much memory as possible. With this change, I am able to remove via virtio-mem (adding individual 128MB memory blocks) 413 out of 448 added memory blocks. Via individual (256MB) DIMMs 380 out of 448 added memory blocks. (I don't have any numbers without this patchset, but looking at the above example, it's at most half of the 448 memory blocks for virtio-mem, and most probably none for DIMMs). Again, there are workloads that might behave very differently due to the nature of ZONE_NORMAL. This change also affects (besides memory onlining): - Other users of undo_isolate_page_range(): Pages are always placed to the tail. -- When memory offlining fails -- When memory isolation fails after having isolated some pageblocks -- When alloc_contig_range() either succeeds or fails - Other users of __putback_isolated_page(): Pages are always placed to the tail. -- Free page reporting - Other users of __free_pages_core() -- AFAIKs, any memory that is getting exposed to the buddy during boot. IIUC we will now usually allocate memory from lower addresses within a zone first (especially during boot). - Other users of generic_online_page() -- Hyper-V balloon This patch (of 5): Let's prepare for additional flags and avoid long parameter lists of bools. Follow-up patches will also make use of the flags in __free_pages_ok(). Signed-off-by:
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Laurent Dufour authored
At boot time, or when doing memory hot-add operations, if the links in sysfs can't be created, the system is still able to run, so just report the error in the kernel log rather than BUG_ON and potentially make system unusable because the callpath can be called with locks held. Since the number of memory blocks managed could be high, the messages are rate limited. As a consequence, link_mem_sections() has no status to report anymore. Signed-off-by:
Laurent Dufour <ldufour@linux.ibm.com> Signed-off-by:
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David Hildenbrand authored
"mem" in the name already indicates the root, similar to release_mem_region() and devm_request_mem_region(). Make it implicit. The only single caller always passes iomem_resource, other parents are not applicable. Suggested-by:
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David Hildenbrand authored
Let's try to merge system ram resources we add, to minimize the number of resources in /proc/iomem. We don't care about the boundaries of individual chunks we added. Signed-off-by:
Wei Liu <wei.liu@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Wei Liu <wei.liu@kernel.org> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: Baoquan He <bhe@redhat.com> Cc: Wei Yang <richardw.yang@linux.intel.com> Cc: Anton Blanchard <anton@ozlabs.org> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jason Wang <jasowang@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Julien Grall <julien@xen.org> Cc: Kees Cook <keescook@chromium.org> Cc: Len Brown <lenb@kernel.org> Cc: Leonardo Bras <leobras.c@gmail.com> Cc: Libor Pechacek <lpechacek@suse.cz> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Nathan Lynch <nathanl@linux.ibm.com> Cc: "Oliver O'Halloran" <oohall@gmail.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Pingfan Liu <kernelfans@gmail.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Roger Pau Monné <roger.pau@citrix.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Link: https://lkml.kernel.org/r/20200911103459.10306-9-david@redhat.comSigned-off-by:
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David Hildenbrand authored
Let's try to merge system ram resources we add, to minimize the number of resources in /proc/iomem. We don't care about the boundaries of individual chunks we added. Signed-off-by:
Juergen Gross <jgross@suse.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Roger Pau Monné <roger.pau@citrix.com> Cc: Julien Grall <julien@xen.org> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: Baoquan He <bhe@redhat.com> Cc: Wei Yang <richardw.yang@linux.intel.com> Cc: Anton Blanchard <anton@ozlabs.org> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jason Wang <jasowang@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Len Brown <lenb@kernel.org> Cc: Leonardo Bras <leobras.c@gmail.com> Cc: Libor Pechacek <lpechacek@suse.cz> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Nathan Lynch <nathanl@linux.ibm.com> Cc: "Oliver O'Halloran" <oohall@gmail.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Pingfan Liu <kernelfans@gmail.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Wei Liu <wei.liu@kernel.org> Link: https://lkml.kernel.org/r/20200911103459.10306-8-david@redhat.comSigned-off-by:
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David Hildenbrand authored
virtio-mem adds memory in memory block granularity, to be able to remove it in the same granularity again later, and to grow slowly on demand. This, however, results in quite a lot of resources when adding a lot of memory. Resources are effectively stored in a list-based tree. Having a lot of resources not only wastes memory, it also makes traversing that tree more expensive, and makes /proc/iomem explode in size (e.g., requiring kexec-tools to manually merge resources later when e.g., trying to create a kdump header). Before this patch, we get (/proc/iomem) when hotplugging 2G via virtio-mem on x86-64: [...] 100000000-13fffffff : System RAM 140000000-33fffffff : virtio0 140000000-147ffffff : System RAM (virtio_mem) 148000000-14fffffff : System RAM (virtio_mem) 150000000-157ffffff : System RAM (virtio_mem) 158000000-15fffffff : System RAM (virtio_mem) 160000000-167ffffff : System RAM (virtio_mem) 168000000-16fffffff : System RAM (virtio_mem) 170000000-177ffffff : System RAM (virtio_mem) 178000000-17fffffff : System RAM (virtio_mem) 180000000-187ffffff : System RAM (virtio_mem) 188000000-18fffffff : System RAM (virtio_mem) 190000000-197ffffff : System RAM (virtio_mem) 198000000-19fffffff : System RAM (virtio_mem) 1a0000000-1a7ffffff : System RAM (virtio_mem) 1a8000000-1afffffff : System RAM (virtio_mem) 1b0000000-1b7ffffff : System RAM (virtio_mem) 1b8000000-1bfffffff : System RAM (virtio_mem) 3280000000-32ffffffff : PCI Bus 0000:00 With this patch, we get (/proc/iomem): [...] fffc0000-ffffffff : Reserved 100000000-13fffffff : System RAM 140000000-33fffffff : virtio0 140000000-1bfffffff : System RAM (virtio_mem) 3280000000-32ffffffff : PCI Bus 0000:00 Of course, with more hotplugged memory, it gets worse. When unplugging memory blocks again, try_remove_memory() (via offline_and_remove_memory()) will properly split the resource up again. Signed-off-by: -
David Hildenbrand authored
Some add_memory*() users add memory in small, contiguous memory blocks. Examples include virtio-mem, hyper-v balloon, and the XEN balloon. This can quickly result in a lot of memory resources, whereby the actual resource boundaries are not of interest (e.g., it might be relevant for DIMMs, exposed via /proc/iomem to user space). We really want to merge added resources in this scenario where possible. Let's provide a flag (MEMHP_MERGE_RESOURCE) to specify that a resource either created within add_memory*() or passed via add_memory_resource() shall be marked mergeable and merged with applicable siblings. To implement that, we need a kernel/resource interface to mark selected System RAM resources mergeable (IORESOURCE_SYSRAM_MERGEABLE) and trigger merging. Note: We really want to merge after the whole operation succeeded, not directly when adding a resource to the resource tree (it would break add_memory_resource() and require splitting resources again when the operation failed - e.g., due to -ENOMEM). Signed-off-by:
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David Hildenbrand authored
We soon want to pass flags, e.g., to mark added System RAM resources. mergeable. Prepare for that. This patch is based on a similar patch by Oscar Salvador: https://lkml.kernel.org/r/20190625075227.15193-3-osalvador@suse.deSigned-off-by:
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David Hildenbrand authored
We soon want to pass flags via a new type to add_memory() and friends. That revealed that we currently don't guard some declarations by CONFIG_MEMORY_HOTPLUG. While some definitions could be moved to different places, let's keep it minimal for now and use CONFIG_MEMORY_HOTPLUG for all functions only compiled with CONFIG_MEMORY_HOTPLUG. Wrap sparse_decode_mem_map() into CONFIG_MEMORY_HOTPLUG, it's only called from CONFIG_MEMORY_HOTPLUG code. While at it, remove allow_online_pfn_range(), which is no longer around, and mhp_notimplemented(), which is unused. Signed-off-by:
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David Hildenbrand authored
IORESOURCE_MEM_DRIVER_MANAGED currently uses an unused PnP bit, which is always set to 0 by hardware. This is far from beautiful (and confusing), and the bit only applies to SYSRAM. So let's move it out of the bus-specific (PnP) defined bits. We'll add another SYSRAM specific bit soon. If we ever need more bits for other purposes, we can steal some from "desc", or reshuffle/regroup what we have. Signed-off-by:
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David Hildenbrand authored
Patch series "selective merging of system ram resources", v4. Some add_memory*() users add memory in small, contiguous memory blocks. Examples include virtio-mem, hyper-v balloon, and the XEN balloon. This can quickly result in a lot of memory resources, whereby the actual resource boundaries are not of interest (e.g., it might be relevant for DIMMs, exposed via /proc/iomem to user space). We really want to merge added resources in this scenario where possible. Resources are effectively stored in a list-based tree. Having a lot of resources not only wastes memory, it also makes traversing that tree more expensive, and makes /proc/iomem explode in size (e.g., requiring kexec-tools to manually merge resources when creating a kdump header. The current kexec-tools resource count limit does not allow for more than ~100GB of memory with a memory block size of 128MB on x86-64). Let's allow to selectively merge system ram resources by specifying a new flag for add_memory*(). Patch #5 contains a /proc/iomem example. Only tested with virtio-mem. This patch (of 8): Let's make sure splitting a resource on memory hotunplug will never fail. This will become more relevant once we merge selected System RAM resources - then, we'll trigger that case more often on memory hotunplug. In general, this function is already unlikely to fail. When we remove memory, we free up quite a lot of metadata (memmap, page tables, memory block device, etc.). The only reason it could really fail would be when injecting allocation errors. All other error cases inside release_mem_region_adjustable() seem to be sanity checks if the function would be abused in different context - let's add WARN_ON_ONCE() in these cases so we can catch them. [natechancellor@gmail.com: fix use of ternary condition in release_mem_region_adjustable] Link: https://lkml.kernel.org/r/20200922060748.2452056-1-natechancellor@gmail.com Link: https://github.com/ClangBuiltLinux/linux/issues/1159Signed-off-by:
Nathan Chancellor <natechancellor@gmail.com> Signed-off-by:
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David Hildenbrand authored
Currently, it can happen that pages are allocated (and freed) via the buddy before we finished basic memory onlining. For example, pages are exposed to the buddy and can be allocated before we actually mark the sections online. Allocated pages could suddenly fail pfn_to_online_page() checks. We had similar issues with pcp handling, when pages are allocated+freed before we reach zone_pcp_update() in online_pages() [1]. Instead, mark all pageblocks MIGRATE_ISOLATE, such that allocations are impossible. Once done with the heavy lifting, use undo_isolate_page_range() to move the pages to the MIGRATE_MOVABLE freelist, marking them ready for allocation. Similar to offline_pages(), we have to manually adjust zone->nr_isolate_pageblock. [1] https://lkml.kernel.org/r/1597150703-19003-1-git-send-email-charante@codeaurora.orgSigned-off-by:
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David Hildenbrand authored
On the memory onlining path, we want to start with MIGRATE_ISOLATE, to un-isolate the pages after memory onlining is complete. Let's allow passing in the migratetype. Signed-off-by:
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David Hildenbrand authored
Commit ac5d2539 ("mm: meminit: reduce number of times pageblocks are set during struct page init") moved the actual zone range check, leaving only the alignment check for pageblocks. Let's drop the stale comment and make the pageblock check easier to read. Signed-off-by:
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David Hildenbrand authored
We don't allow to offline memory with holes, all boot memory is online, and all hotplugged memory cannot have holes. We can now simplify onlining of pages. As we only allow to online/offline full sections and sections always span full MAX_ORDER_NR_PAGES, we can just process MAX_ORDER - 1 pages without further special handling. The number of onlined pages simply corresponds to the number of pages we were requested to online. While at it, refine the comment regarding the callback not exposing all pages to the buddy. Signed-off-by:
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David Hildenbrand authored
Callers no longer need the number of isolated pageblocks. Let's simplify. Signed-off-by:
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David Hildenbrand authored
We make sure that we cannot have any memory holes right at the beginning of offline_pages() and we only support to online/offline full sections. Both, sections and pageblocks are a power of two in size, and sections always span full pageblocks. We can directly calculate the number of isolated pageblocks from nr_pages. Signed-off-by:
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David Hildenbrand authored
offline_pages() is the only user. __offline_isolated_pages() never gets called with ranges that contain memory holes and we no longer care about the return value. Drop the return value handling and all pfn_valid() checks. Update the documentation. Signed-off-by:
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David Hildenbrand authored
We make sure that we cannot have any memory holes right at the beginning of offline_pages(). We no longer need walk_system_ram_range() and can call test_pages_isolated() and __offline_isolated_pages() directly. offlined_pages always corresponds to nr_pages, so we can simplify that. [akpm@linux-foundation.org: patch conflict resolution] Signed-off-by:
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David Hildenbrand authored
Already two people (including me) tried to offline subsections, because the function looks like it can deal with it. But we really can only online/offline full sections that are properly aligned (e.g., we can only mark full sections online/offline via SECTION_IS_ONLINE). Add a simple safety net to document the restriction now. Current users (core and powernv/memtrace) respect these restrictions. Signed-off-by:
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David Hildenbrand authored
Patch series "mm/memory_hotplug: online_pages()/offline_pages() cleanups", v2. These are a bunch of cleanups for online_pages()/offline_pages() and related code, mostly getting rid of memory hole handling that is no longer necessary. There is only a single walk_system_ram_range() call left in offline_pages(), to make sure we don't have any memory holes. I had some of these patches lying around for a longer time but didn't have time to polish them. In addition, the last patch marks all pageblocks of memory to get onlined MIGRATE_ISOLATE, so pages that have just been exposed to the buddy cannot get allocated before onlining is complete. Once heavy lifting is done, the pageblocks are set to MIGRATE_MOVABLE, such that allocations are possible. I played with DIMMs and virtio-mem on x86-64 and didn't spot any surprises. I verified that the numer of isolated pageblocks is correctly handled when onlining/offlining. This patch (of 10): There is only a single user, offline_pages(). Let's inline, to make it look more similar to online_pages(). Signed-off-by:
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Jann Horn authored
The comment talks about having to hold mmget() (which means mm_users), but the actual check is on mm_count (which would be mmgrab()). Given that MMU notifiers are torn down in mmput() -> __mmput() -> exit_mmap() -> mmu_notifier_release(), I believe that the comment is correct and the check should be on mm->mm_users. Fix it up accordingly. Fixes: 99cb252f ("mm/mmu_notifier: add an interval tree notifier") Signed-off-by:
Jann Horn <jannh@google.com> Signed-off-by:
Jason Gunthorpe <jgg@nvidia.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Christian König <christian.koenig@amd.com Link: https://lkml.kernel.org/r/20200901000143.207585-1-jannh@google.comSigned-off-by:
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Bartosz Golaszewski authored
Memory allocated with kstrdup_const() must not be passed to regular krealloc() as it is not aware of the possibility of the chunk residing in .rodata. Since there are no potential users of krealloc_const() at the moment, let's just update the doc to make it explicit. Signed-off-by:
Bartosz Golaszewski <bgolaszewski@baylibre.com> Signed-off-by:
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Miaohe Lin authored
Use helper macro abs() to simplify the "x > t || x < -t" cmp. Signed-off-by:
Miaohe Lin <linmiaohe@huawei.com> Signed-off-by:
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Mateusz Nosek authored
Variable 'want_page_poisoning' is a switch deciding if page poisoning should be enabled. This patch changes it to be static key. Signed-off-by:
Mateusz Nosek <mateusznosek0@gmail.com> Signed-off-by:
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Oscar Salvador authored
Aristeu Rozanski reported that a customer test case started to report -EBUSY after the hwpoison rework patchset. There is a race window between spotting a free page and taking it off its buddy freelist, so it might be that by the time we try to take it off, the page has been already allocated. This patch tries to handle such race window by trying to handle the new type of page again if the page was allocated under us. Reported-by:
Aristeu Rozanski <aris@ruivo.org> Signed-off-by:
Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Dmitry Yakunin <zeil@yandex-team.ru> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Oscar Salvador <osalvador@suse.com> Cc: Qian Cai <cai@lca.pw> Cc: Tony Luck <tony.luck@intel.com> Link: https://lkml.kernel.org/r/20200922135650.1634-15-osalvador@suse.deSigned-off-by:
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Naoya Horiguchi authored
Soft offlining could fail with EIO due to the race condition with hugepage migration. This issuse became visible due to the change by previous patch that makes soft offline handler take page refcount by its own. We have no way to directly pin zero refcount page, and the page considered as a zero refcount page could be allocated just after the first check. This patch adds the second check to find the race and gives us chance to handle it more reliably. Reported-by:
Qian Cai <cai@lca.pw> Signed-off-by:
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Naoya Horiguchi authored
memory_failure() is supposed to call action_result() when it handles a memory error event, but there's one missing case. So let's add it. I find that include/ras/ras_event.h has some other MF_MSG_* undefined, so this patch also adds them. Signed-off-by:
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Oscar Salvador authored
Currently, there is an inconsistency when calling soft-offline from different paths on a page that is already poisoned. 1) madvise: madvise_inject_error skips any poisoned page and continues the loop. If that was the only page to madvise, it returns 0. 2) /sys/devices/system/memory/: When calling soft_offline_page_store()->soft_offline_page(), we return -EBUSY in case the page is already poisoned. This is inconsistent with a) the above example and b) memory_failure, where we return 0 if the page was poisoned. Fix this by dropping the PageHWPoison() check in madvise_inject_error, and let soft_offline_page return 0 if it finds the page already poisoned. Please, note that this represents a user-api change, since now the return error when calling soft_offline_page_store()->soft_offline_page() will be different. Signed-off-by: -
Oscar Salvador authored
Merging soft_offline_huge_page and __soft_offline_page let us get rid of quite some duplicated code, and makes the code much easier to follow. Now, __soft_offline_page will handle both normal and hugetlb pages. Signed-off-by:
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Oscar Salvador authored
This patch changes the way we set and handle in-use poisoned pages. Until now, poisoned pages were released to the buddy allocator, trusting that the checks that take place at allocation time would act as a safe net and would skip that page. This has proved to be wrong, as we got some pfn walkers out there, like compaction, that all they care is the page to be in a buddy freelist. Although this might not be the only user, having poisoned pages in the buddy allocator seems a bad idea as we should only have free pages that are ready and meant to be used as such. Before explaining the taken approach, let us break down the kind of pages we can soft offline. - Anonymous THP (after the split, they end up being 4K pages) - Hugetlb - Order-0 pages (that can be either migrated or invalited) * Normal pages (order-0 and anon-THP) - If they are clean and unmapped page cache pages, we invalidate then by means of invalidate_inode_page(). - If they are mapped/dirty, we do the isolate-and-migrate dance. Either way, do not call put_page directly from those paths. Instead, we keep the page and send it to page_handle_poison to perform the right handling. page_handle_poison sets the HWPoison flag and does the last put_page. Down the chain, we placed a check for HWPoison page in free_pages_prepare, that just skips any poisoned page, so those pages do not end up in any pcplist/freelist. After that, we set the refcount on the page to 1 and we increment the poisoned pages counter. If we see that the check in free_pages_prepare creates trouble, we can always do what we do for free pages: - wait until the page hits buddy's freelists - take it off, and flag it The downside of the above approach is that we could race with an allocation, so by the time we want to take the page off the buddy, the page has been already allocated so we cannot soft offline it. But the user could always retry it. * Hugetlb pages - We isolate-and-migrate them After the migration has been successful, we call dissolve_free_huge_page, and we set HWPoison on the page if we succeed. Hugetlb has a slightly different handling though. While for non-hugetlb pages we cared about closing the race with an allocation, doing so for hugetlb pages requires quite some additional and intrusive code (we would need to hook in free_huge_page and some other places). So I decided to not make the code overly complicated and just fail normally if the page we allocated in the meantime. We can always build on top of this. As a bonus, because of the way we handle now in-use pages, we no longer need the put-as-isolation-migratetype dance, that was guarding for poisoned pages to end up in pcplists. Signed-off-by: -
Oscar Salvador authored
When trying to soft-offline a free page, we need to first take it off the buddy allocator. Once we know is out of reach, we can safely flag it as poisoned. take_page_off_buddy will be used to take a page meant to be poisoned off the buddy allocator. take_page_off_buddy calls break_down_buddy_pages, which splits a higher-order page in case our page belongs to one. Once the page is under our control, we call page_handle_poison to set it as poisoned and grab a refcount on it. Signed-off-by:
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Oscar Salvador authored
Place the THP's page handling in a helper and use it from both hard and soft-offline machinery, so we get rid of some duplicated code. Signed-off-by:
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Oscar Salvador authored
After commit 4e41a30c ("mm: hwpoison: adjust for new thp refcounting"), put_hwpoison_page got reduced to a put_page. Let us just use put_page instead. Signed-off-by:
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Oscar Salvador authored
Make a proper if-else condition for {hard,soft}-offline. Signed-off-by:Oscar Salvador <osalvador@suse.com> Signed-off-by:
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Oscar Salvador authored
Since get_hwpoison_page is only used in memory-failure code now, let us un-export it and make it private to that code. Signed-off-by:
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Naoya Horiguchi authored
Another memory error injection interface debugfs:hwpoison/corrupt-pfn also takes bogus refcount for hwpoison_filter(). It's justified because this does a coarse filter, expecting that memory_failure() redoes the check for sure. Signed-off-by:
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