- 28 Dec, 2018 40 commits
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Mel Gorman authored
This is a preparation patch that copies the GFP flag __GFP_KSWAPD_RECLAIM into alloc_flags. This is a preparation patch only that avoids having to pass gfp_mask through a long callchain in a future patch. Note that the setting in the fast path happens in alloc_flags_nofragment() and it may be claimed that this has nothing to do with ALLOC_NO_FRAGMENT. That's true in this patch but is not true later so it's done now for easier review to show where the flag needs to be recorded. No functional change. [mgorman@techsingularity.net: ALLOC_KSWAPD flag needs to be applied in the !CONFIG_ZONE_DMA32 case] Link: http://lkml.kernel.org/r/20181126143503.GO23260@techsingularity.net Link: http://lkml.kernel.org/r/20181123114528.28802-4-mgorman@techsingularity.netSigned-off-by:
Mel Gorman <mgorman@techsingularity.net> Reviewed-by:
Andrew Morton <akpm@linux-foundation.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Zi Yan <zi.yan@cs.rutgers.edu> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Mel Gorman authored
This is a preparation patch only, no functional change. Link: http://lkml.kernel.org/r/20181123114528.28802-3-mgorman@techsingularity.netSigned-off-by:
Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Zi Yan <zi.yan@cs.rutgers.edu> Signed-off-by:
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Mel Gorman authored
Patch series "Fragmentation avoidance improvements", v5. It has been noted before that fragmentation avoidance (aka anti-fragmentation) is not perfect. Given sufficient time or an adverse workload, memory gets fragmented and the long-term success of high-order allocations degrades. This series defines an adverse workload, a definition of external fragmentation events (including serious) ones and a series that reduces the level of those fragmentation events. The details of the workload and the consequences are described in more detail in the changelogs. However, from patch 1, this is a high-level summary of the adverse workload. The exact details are found in the mmtests implementation. The broad details of the workload are as follows; 1. Create an XFS filesystem (not specified in the configuration but done as part of the testing for this patch) 2. Start 4 fio threads that write a number of 64K files inefficiently. Inefficiently means that files are created on first access and not created in advance (fio parameterr create_on_open=1) and fallocate is not used (fallocate=none). With multiple IO issuers this creates a mix of slab and page cache allocations over time. The total size of the files is 150% physical memory so that the slabs and page cache pages get mixed 3. Warm up a number of fio read-only threads accessing the same files created in step 2. This part runs for the same length of time it took to create the files. It'll fault back in old data and further interleave slab and page cache allocations. As it's now low on memory due to step 2, fragmentation occurs as pageblocks get stolen. 4. While step 3 is still running, start a process that tries to allocate 75% of memory as huge pages with a number of threads. The number of threads is based on a (NR_CPUS_SOCKET - NR_FIO_THREADS)/4 to avoid THP threads contending with fio, any other threads or forcing cross-NUMA scheduling. Note that the test has not been used on a machine with less than 8 cores. The benchmark records whether huge pages were allocated and what the fault latency was in microseconds 5. Measure the number of events potentially causing external fragmentation, the fault latency and the huge page allocation success rate. 6. Cleanup Overall the series reduces external fragmentation causing events by over 94% on 1 and 2 socket machines, which in turn impacts high-order allocation success rates over the long term. There are differences in latencies and high-order allocation success rates. Latencies are a mixed bag as they are vulnerable to exact system state and whether allocations succeeded so they are treated as a secondary metric. Patch 1 uses lower zones if they are populated and have free memory instead of fragmenting a higher zone. It's special cased to handle a Normal->DMA32 fallback with the reasons explained in the changelog. Patch 2-4 boosts watermarks temporarily when an external fragmentation event occurs. kswapd wakes to reclaim a small amount of old memory and then wakes kcompactd on completion to recover the system slightly. This introduces some overhead in the slowpath. The level of boosting can be tuned or disabled depending on the tolerance for fragmentation vs allocation latency. Patch 5 stalls some movable allocation requests to let kswapd from patch 4 make some progress. The duration of the stalls is very low but it is possible to tune the system to avoid fragmentation events if larger stalls can be tolerated. The bulk of the improvement in fragmentation avoidance is from patches 1-4 but patch 5 can deal with a rare corner case and provides the option of tuning a system for THP allocation success rates in exchange for some stalls to control fragmentation. This patch (of 5): The page allocator zone lists are iterated based on the watermarks of each zone which does not take anti-fragmentation into account. On x86, node 0 may have multiple zones while other nodes have one zone. A consequence is that tasks running on node 0 may fragment ZONE_NORMAL even though ZONE_DMA32 has plenty of free memory. This patch special cases the allocator fast path such that it'll try an allocation from a lower local zone before fragmenting a higher zone. In this case, stealing of pageblocks or orders larger than a pageblock are still allowed in the fast path as they are uninteresting from a fragmentation point of view. This was evaluated using a benchmark designed to fragment memory before attempting THP allocations. It's implemented in mmtests as the following configurations configs/config-global-dhp__workload_thpfioscale configs/config-global-dhp__workload_thpfioscale-defrag configs/config-global-dhp__workload_thpfioscale-madvhugepage e.g. from mmtests ./run-mmtests.sh --run-monitor --config configs/config-global-dhp__workload_thpfioscale test-run-1 The broad details of the workload are as follows; 1. Create an XFS filesystem (not specified in the configuration but done as part of the testing for this patch). 2. Start 4 fio threads that write a number of 64K files inefficiently. Inefficiently means that files are created on first access and not created in advance (fio parameter create_on_open=1) and fallocate is not used (fallocate=none). With multiple IO issuers this creates a mix of slab and page cache allocations over time. The total size of the files is 150% physical memory so that the slabs and page cache pages get mixed. 3. Warm up a number of fio read-only processes accessing the same files created in step 2. This part runs for the same length of time it took to create the files. It'll refault old data and further interleave slab and page cache allocations. As it's now low on memory due to step 2, fragmentation occurs as pageblocks get stolen. 4. While step 3 is still running, start a process that tries to allocate 75% of memory as huge pages with a number of threads. The number of threads is based on a (NR_CPUS_SOCKET - NR_FIO_THREADS)/4 to avoid THP threads contending with fio, any other threads or forcing cross-NUMA scheduling. Note that the test has not been used on a machine with less than 8 cores. The benchmark records whether huge pages were allocated and what the fault latency was in microseconds. 5. Measure the number of events potentially causing external fragmentation, the fault latency and the huge page allocation success rate. 6. Cleanup the test files. Note that due to the use of IO and page cache that this benchmark is not suitable for running on large machines where the time to fragment memory may be excessive. Also note that while this is one mix that generates fragmentation that it's not the only mix that generates fragmentation. Differences in workload that are more slab-intensive or whether SLUB is used with high-order pages may yield different results. When the page allocator fragments memory, it records the event using the mm_page_alloc_extfrag ftrace event. If the fallback_order is smaller than a pageblock order (order-9 on 64-bit x86) then it's considered to be an "external fragmentation event" that may cause issues in the future. Hence, the primary metric here is the number of external fragmentation events that occur with order < 9. The secondary metric is allocation latency and huge page allocation success rates but note that differences in latencies and what the success rate also can affect the number of external fragmentation event which is why it's a secondary metric. 1-socket Skylake machine config-global-dhp__workload_thpfioscale XFS (no special madvise) 4 fio threads, 1 THP allocating thread -------------------------------------- 4.20-rc3 extfrag events < order 9: 804694 4.20-rc3+patch: 408912 (49% reduction) thpfioscale Fault Latencies 4.20.0-rc3 4.20.0-rc3 vanilla lowzone-v5r8 Amean fault-base-1 662.92 ( 0.00%) 653.58 * 1.41%* Amean fault-huge-1 0.00 ( 0.00%) 0.00 ( 0.00%) 4.20.0-rc3 4.20.0-rc3 vanilla lowzone-v5r8 Percentage huge-1 0.00 ( 0.00%) 0.00 ( 0.00%) Fault latencies are slightly reduced while allocation success rates remain at zero as this configuration does not make any special effort to allocate THP and fio is heavily active at the time and either filling memory or keeping pages resident. However, a 49% reduction of serious fragmentation events reduces the changes of external fragmentation being a problem in the future. Vlastimil asked during review for a breakdown of the allocation types that are falling back. vanilla 3816 MIGRATE_UNMOVABLE 800845 MIGRATE_MOVABLE 33 MIGRATE_UNRECLAIMABLE patch 735 MIGRATE_UNMOVABLE 408135 MIGRATE_MOVABLE 42 MIGRATE_UNRECLAIMABLE The majority of the fallbacks are due to movable allocations and this is consistent for the workload throughout the series so will not be presented again as the primary source of fallbacks are movable allocations. Movable fallbacks are sometimes considered "ok" to fallback because they can be migrated. The problem is that they can fill an unmovable/reclaimable pageblock causing those allocations to fallback later and polluting pageblocks with pages that cannot move. If there is a movable fallback, it is pretty much guaranteed to affect an unmovable/reclaimable pageblock and while it might not be enough to actually cause a unmovable/reclaimable fallback in the future, we cannot know that in advance so the patch takes the only option available to it. Hence, it's important to control them. This point is also consistent throughout the series and will not be repeated. 1-socket Skylake machine global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE) ----------------------------------------------------------------- 4.20-rc3 extfrag events < order 9: 291392 4.20-rc3+patch: 191187 (34% reduction) thpfioscale Fault Latencies 4.20.0-rc3 4.20.0-rc3 vanilla lowzone-v5r8 Amean fault-base-1 1495.14 ( 0.00%) 1467.55 ( 1.85%) Amean fault-huge-1 1098.48 ( 0.00%) 1127.11 ( -2.61%) thpfioscale Percentage Faults Huge 4.20.0-rc3 4.20.0-rc3 vanilla lowzone-v5r8 Percentage huge-1 78.57 ( 0.00%) 77.64 ( -1.18%) Fragmentation events were reduced quite a bit although this is known to be a little variable. The latencies and allocation success rates are similar but they were already quite high. 2-socket Haswell machine config-global-dhp__workload_thpfioscale XFS (no special madvise) 4 fio threads, 5 THP allocating threads ---------------------------------------------------------------- 4.20-rc3 extfrag events < order 9: 215698 4.20-rc3+patch: 200210 (7% reduction) thpfioscale Fault Latencies 4.20.0-rc3 4.20.0-rc3 vanilla lowzone-v5r8 Amean fault-base-5 1350.05 ( 0.00%) 1346.45 ( 0.27%) Amean fault-huge-5 4181.01 ( 0.00%) 3418.60 ( 18.24%) 4.20.0-rc3 4.20.0-rc3 vanilla lowzone-v5r8 Percentage huge-5 1.15 ( 0.00%) 0.78 ( -31.88%) The reduction of external fragmentation events is slight and this is partially due to the removal of __GFP_THISNODE in commit ac5b2c18 ("mm: thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings") as THP allocations can now spill over to remote nodes instead of fragmenting local memory. 2-socket Haswell machine global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE) ----------------------------------------------------------------- 4.20-rc3 extfrag events < order 9: 166352 4.20-rc3+patch: 147463 (11% reduction) thpfioscale Fault Latencies 4.20.0-rc3 4.20.0-rc3 vanilla lowzone-v5r8 Amean fault-base-5 6138.97 ( 0.00%) 6217.43 ( -1.28%) Amean fault-huge-5 2294.28 ( 0.00%) 3163.33 * -37.88%* thpfioscale Percentage Faults Huge 4.20.0-rc3 4.20.0-rc3 vanilla lowzone-v5r8 Percentage huge-5 96.82 ( 0.00%) 95.14 ( -1.74%) There was a slight reduction in external fragmentation events although the latencies were higher. The allocation success rate is high enough that the system is struggling and there is quite a lot of parallel reclaim and compaction activity. There is also a certain degree of luck on whether processes start on node 0 or not for this patch but the relevance is reduced later in the series. Overall, the patch reduces the number of external fragmentation causing events so the success of THP over long periods of time would be improved for this adverse workload. Link: http://lkml.kernel.org/r/20181123114528.28802-2-mgorman@techsingularity.netSigned-off-by: -
David Hildenbrand authored
Userspace should always be in charge of how to online memory and if memory should be onlined automatically in the kernel. Let's drop the parameter to overwrite this - XEN passes memhp_auto_online, just like add_memory(), so we can directly use that instead internally. Link: http://lkml.kernel.org/r/20181123123740.27652-1-david@redhat.comSigned-off-by:
David Hildenbrand <david@redhat.com> Acked-by:
Michal Hocko <mhocko@suse.com> Reviewed-by:
Oscar Salvador <osalvador@suse.de> Acked-by:
Juergen Gross <jgross@suse.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Cc: David Hildenbrand <david@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Arun KS <arunks@codeaurora.org> Cc: Mathieu Malaterre <malat@debian.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by:
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Wei Yang authored
In cb5e39b8 ("drivers: base: refactor add_memory_section() to add_memory_block()"), add_memory_block() is introduced, which is only invoked in memory_dev_init(). When combining these two loops in memory_dev_init() and add_memory_block(), they looks like this: for (i = 0; i < NR_MEM_SECTIONS; i += sections_per_block) for (j = i; (j < i + sections_per_block) && j < NR_MEM_SECTIONS; j++) Since it is sure the (i < NR_MEM_SECTIONS) and j sits in its own memory block, the check of (j < NR_MEM_SECTIONS) is not necessary. This patch just removes this check. Link: http://lkml.kernel.org/r/20181123222811.18216-1-richard.weiyang@gmail.comSigned-off-by:
Wei Yang <richard.weiyang@gmail.com> Reviewed-by:
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Mike Rapoport authored
__memblock_free_early() is only used by the convenience wrappers, so essentially we wrap a call to memblock_free() twice. Replace calls of __memblock_free_early() with calls to memblock_free() and drop the former. Link: http://lkml.kernel.org/r/20181125102940.GE28634@rapoport-lnxSigned-off-by:
Mike Rapoport <rppt@linux.ibm.com> Reviewed-by:
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Wentao Wang authored
Link: http://lkml.kernel.org/r/C8ECE1B7A767434691FEEFA3A01765D72AFB8E78@MX203CL03.corp.emc.comSigned-off-by:
Wentao Wang <witallwang@gmail.com> Reviewed-by:
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Aaron Lu authored
There are multiple places of freeing a page, they all do the same things so a common function can be used to reduce code duplicate. It also avoids bug fixed in one function but left in another. Link: http://lkml.kernel.org/r/20181119134834.17765-3-aaron.lu@intel.comSigned-off-by:
Aaron Lu <aaron.lu@intel.com> Acked-by:
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Aaron Lu authored
page_frag_free() calls __free_pages_ok() to free the page back to Buddy. This is OK for high order page, but for order-0 pages, it misses the optimization opportunity of using Per-Cpu-Pages and can cause zone lock contention when called frequently. Pawel Staszewski recently shared his result of 'how Linux kernel handles normal traffic'[1] and from perf data, Jesper Dangaard Brouer found the lock contention comes from page allocator: mlx5e_poll_tx_cq | --16.34%--napi_consume_skb | |--12.65%--__free_pages_ok | | | --11.86%--free_one_page | | | |--10.10%--queued_spin_lock_slowpath | | | --0.65%--_raw_spin_lock | |--1.55%--page_frag_free | --1.44%--skb_release_data Jesper explained how it happened: mlx5 driver RX-page recycle mechanism is not effective in this workload and pages have to go through the page allocator. The lock contention happens during mlx5 DMA TX completion cycle. And the page allocator cannot keep up at these speeds.[2] I thought that __free_pages_ok() are mostly freeing high order pages and thought this is an lock contention for high order pages but Jesper explained in detail that __free_pages_ok() here are actually freeing order-0 pages because mlx5 is using order-0 pages to satisfy its page pool allocation request.[3] The free path as pointed out by Jesper is: skb_free_head() -> skb_free_frag() -> page_frag_free() And the pages being freed on this path are order-0 pages. Fix this by doing similar things as in __page_frag_cache_drain() - send the being freed page to PCP if it's an order-0 page, or directly to Buddy if it is a high order page. With this change, Paweł hasn't noticed lock contention yet in his workload and Jesper has noticed a 7% performance improvement using a micro benchmark and lock contention is gone. Ilias' test on a 'low' speed 1Gbit interface on an cortex-a53 shows ~11% performance boost testing with 64byte packets and __free_pages_ok() disappeared from perf top. [1]: https://www.spinics.net/lists/netdev/msg531362.html [2]: https://www.spinics.net/lists/netdev/msg531421.html [3]: https://www.spinics.net/lists/netdev/msg531556.html [akpm@linux-foundation.org: add comment] Link: http://lkml.kernel.org/r/20181120014544.GB10657@intel.comSigned-off-by:Pawel Staszewski <pstaszewski@itcare.pl> Analysed-by:
Jesper Dangaard Brouer <brouer@redhat.com> Acked-by:
Ilias Apalodimas <ilias.apalodimas@linaro.org> Tested-by:
Alexander Duyck <alexander.h.duyck@linux.intel.com> Acked-by:
Tariq Toukan <tariqt@mellanox.com> Acked-by:
Pankaj gupta <pagupta@redhat.com> Signed-off-by:
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Dan Williams authored
At Maintainer Summit, Greg brought up a topic I proposed around EXPORT_SYMBOL_GPL usage. The motivation was considerations for when EXPORT_SYMBOL_GPL is warranted and the criteria for taking the exceptional step of reclassifying an existing export. Specifically, I wanted to make the case that although the line is fuzzy and hard to specify in abstract terms, it is nonetheless clear that devm_memremap_pages() and HMM (Heterogeneous Memory Management) have crossed it. The devm_memremap_pages() facility should have been EXPORT_SYMBOL_GPL from the beginning, and HMM as a derivative of that functionality should have naturally picked up that designation as well. Contrary to typical rules, the HMM infrastructure was merged upstream with zero in-tree consumers. There was a promise at the time that those users would be merged "soon", but it has been over a year with no drivers arriving. While the Nouveau driver is about to belatedly make good on that promise it is clear that HMM was targeted first and foremost at an out-of-tree consumer. HMM is derived from devm_memremap_pages(), a facility Christoph and I spearheaded to support persistent memory. It combines a device lifetime model with a dynamically created 'struct page' / memmap array for any physical address range. It enables coordination and control of the many code paths in the kernel built to interact with memory via 'struct page' objects. With HMM the integration goes even deeper by allowing device drivers to hook and manipulate page fault and page free events. One interpretation of when EXPORT_SYMBOL is suitable is when it is exporting stable and generic leaf functionality. The devm_memremap_pages() facility continues to see expanding use cases, peer-to-peer DMA being the most recent, with no clear end date when it will stop attracting reworks and semantic changes. It is not suitable to export devm_memremap_pages() as a stable 3rd party driver API due to the fact that it is still changing and manipulates core behavior. Moreover, it is not in the best interest of the long term development of the core memory management subsystem to permit any external driver to effectively define its own system-wide memory management policies with no encouragement to engage with upstream. I am also concerned that HMM was designed in a way to minimize further engagement with the core-MM. That, with these hooks in place, device-drivers are free to implement their own policies without much consideration for whether and how the core-MM could grow to meet that need. Going forward not only should HMM be EXPORT_SYMBOL_GPL, but the core-MM should be allowed the opportunity and stimulus to change and address these new use cases as first class functionality. Original changelog: hmm_devmem_add(), and hmm_devmem_add_resource() duplicated devm_memremap_pages() and are now simple now wrappers around the core facility to inject a dev_pagemap instance into the global pgmap_radix and hook page-idle events. The devm_memremap_pages() interface is base infrastructure for HMM. HMM has more and deeper ties into the kernel memory management implementation than base ZONE_DEVICE which is itself a EXPORT_SYMBOL_GPL facility. Originally, the HMM page structure creation routines copied the devm_memremap_pages() code and reused ZONE_DEVICE. A cleanup to unify the implementations was discussed during the initial review: http://lkml.iu.edu/hypermail/linux/kernel/1701.2/00812.html Recent work to extend devm_memremap_pages() for the peer-to-peer-DMA facility enabled this cleanup to move forward. In addition to the integration with devm_memremap_pages() HMM depends on other GPL-only symbols: mmu_notifier_unregister_no_release percpu_ref region_intersects __class_create It goes further to consume / indirectly expose functionality that is not exported to any other driver: alloc_pages_vma walk_page_range HMM is derived from devm_memremap_pages(), and extends deep core-kernel fundamentals. Similar to devm_memremap_pages(), mark its entry points EXPORT_SYMBOL_GPL(). [logang@deltatee.com: PCI/P2PDMA: match interface changes to devm_memremap_pages()] Link: http://lkml.kernel.org/r/20181130225911.2900-1-logang@deltatee.com Link: http://lkml.kernel.org/r/154275560565.76910.15919297436557795278.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by:
Dan Williams <dan.j.williams@intel.com> Signed-off-by:
Logan Gunthorpe <logang@deltatee.com> Reviewed-by:
Christoph Hellwig <hch@lst.de> Cc: Logan Gunthorpe <logang@deltatee.com> Cc: "Jérôme Glisse" <jglisse@redhat.com> Cc: Balbir Singh <bsingharora@gmail.com>, Cc: Michal Hocko <mhocko@suse.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: <stable@vger.kernel.org> Signed-off-by:
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Dan Williams authored
Commit e8d51348 ("memremap: change devm_memremap_pages interface to use struct dev_pagemap") refactored devm_memremap_pages() to allow a dev_pagemap instance to be supplied. Passing in a dev_pagemap interface simplifies the design of pgmap type drivers in that they can rely on container_of() to lookup any private data associated with the given dev_pagemap instance. In addition to the cleanups this also gives hmm users multi-order-radix improvements that arrived with commit ab1b597e "mm, devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups" As part of the conversion to the devm_memremap_pages() method of handling the percpu_ref relative to when pages are put, the percpu_ref completion needs to move to hmm_devmem_ref_exit(). See 71389703 ("mm, zone_device: Replace {get, put}_zone_device_page...") for details. Link: http://lkml.kernel.org/r/154275560053.76910.10870962637383152392.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by:
Jérôme Glisse <jglisse@redhat.com> Acked-by:
Balbir Singh <bsingharora@gmail.com> Cc: Logan Gunthorpe <logang@deltatee.com> Cc: Michal Hocko <mhocko@suse.com> Cc: <stable@vger.kernel.org> Signed-off-by:
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Dan Williams authored
devm semantics arrange for resources to be torn down when device-driver-probe fails or when device-driver-release completes. Similar to devm_memremap_pages() there is no need to support an explicit remove operation when the users properly adhere to devm semantics. Note that devm_kzalloc() automatically handles allocating node-local memory. Link: http://lkml.kernel.org/r/154275559545.76910.9186690723515469051.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by:
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Dan Williams authored
In preparation for consolidating all ZONE_DEVICE enabling via devm_memremap_pages(), teach it how to handle the constraints of MEMORY_DEVICE_PRIVATE ranges. [jglisse@redhat.com: call move_pfn_range_to_zone for MEMORY_DEVICE_PRIVATE] Link: http://lkml.kernel.org/r/154275559036.76910.12434636179931292607.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by:
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Dan Williams authored
The last step before devm_memremap_pages() returns success is to allocate a release action, devm_memremap_pages_release(), to tear the entire setup down. However, the result from devm_add_action() is not checked. Checking the error from devm_add_action() is not enough. The api currently relies on the fact that the percpu_ref it is using is killed by the time the devm_memremap_pages_release() is run. Rather than continue this awkward situation, offload the responsibility of killing the percpu_ref to devm_memremap_pages_release() directly. This allows devm_memremap_pages() to do the right thing relative to init failures and shutdown. Without this change we could fail to register the teardown of devm_memremap_pages(). The likelihood of hitting this failure is tiny as small memory allocations almost always succeed. However, the impact of the failure is large given any future reconfiguration, or disable/enable, of an nvdimm namespace will fail forever as subsequent calls to devm_memremap_pages() will fail to setup the pgmap_radix since there will be stale entries for the physical address range. An argument could be made to require that the ->kill() operation be set in the @pgmap arg rather than passed in separately. However, it helps code readability, tracking the lifetime of a given instance, to be able to grep the kill routine directly at the devm_memremap_pages() call site. Link: http://lkml.kernel.org/r/154275558526.76910.7535251937849268605.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by:
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Dan Williams authored
Given the fact that devm_memremap_pages() requires a percpu_ref that is torn down by devm_memremap_pages_release() the current support for mapping RAM is broken. Support for remapping "System RAM" has been broken since the beginning and there is no existing user of this this code path, so just kill the support and make it an explicit error. This cleanup also simplifies a follow-on patch to fix the error path when setting a devm release action for devm_memremap_pages_release() fails. Link: http://lkml.kernel.org/r/154275557997.76910.14689813630968180480.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by:
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Dan Williams authored
devm_memremap_pages() is a facility that can create struct page entries for any arbitrary range and give drivers the ability to subvert core aspects of page management. Specifically the facility is tightly integrated with the kernel's memory hotplug functionality. It injects an altmap argument deep into the architecture specific vmemmap implementation to allow allocating from specific reserved pages, and it has Linux specific assumptions about page structure reference counting relative to get_user_pages() and get_user_pages_fast(). It was an oversight and a mistake that this was not marked EXPORT_SYMBOL_GPL from the outset. Again, devm_memremap_pagex() exposes and relies upon core kernel internal assumptions and will continue to evolve along with 'struct page', memory hotplug, and support for new memory types / topologies. Only an in-kernel GPL-only driver is expected to keep up with this ongoing evolution. This interface, and functionality derived from this interface, is not suitable for kernel-external drivers. Link: http://lkml.kernel.org/r/154275557457.76910.16923571232582744134.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by:
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Huang Shijie authored
In the enum migratetype definition, MIGRATE_MOVABLE is before MIGRATE_RECLAIMABLE. Change the order of them to match the enumeration's order. Link: http://lkml.kernel.org/r/20181121085821.3442-1-sjhuang@iluvatar.aiSigned-off-by:
Huang Shijie <sjhuang@iluvatar.ai> Reviewed-by:
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Eric Biggers authored
Reference counters should use refcount_t rather than atomic_t, since the refcount_t implementation can prevent overflows, reducing the exploitability of reference leak bugs. userfaultfd_ctx::refcount is a reference counter with the usual semantics, so convert it to refcount_t. Note: I replaced the BUG() on incrementing a 0 refcount with just refcount_inc(), since part of the semantics of refcount_t is that that incrementing a 0 refcount is not allowed; with CONFIG_REFCOUNT_FULL, refcount_inc() already checks for it and warns. Link: http://lkml.kernel.org/r/20181115003916.63381-1-ebiggers@kernel.orgSigned-off-by:
Eric Biggers <ebiggers@google.com> Reviewed-by:
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Aaron Lu authored
Since a2468cc9 ("swap: choose swap device according to numa node"), avail_lists field of swap_info_struct is changed to an array with MAX_NUMNODES elements. This made swap_info_struct size increased to 40KiB and needs an order-4 page to hold it. This is not optimal in that: 1 Most systems have way less than MAX_NUMNODES(1024) nodes so it is a waste of memory; 2 It could cause swapon failure if the swap device is swapped on after system has been running for a while, due to no order-4 page is available as pointed out by Vasily Averin. Solve the above two issues by using nr_node_ids(which is the actual possible node number the running system has) for avail_lists instead of MAX_NUMNODES. nr_node_ids is unknown at compile time so can't be directly used when declaring this array. What I did here is to declare avail_lists as zero element array and allocate space for it when allocating space for swap_info_struct. The reason why keep using array but not pointer is plist_for_each_entry needs the field to be part of the struct, so pointer will not work. This patch is on top of Vasily Averin's fix commit. I think the use of kvzalloc for swap_info_struct is still needed in case nr_node_ids is really big on some systems. Link: http://lkml.kernel.org/r/20181115083847.GA11129@intel.comSigned-off-by:
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Wei Yang authored
Commit fa5e084e ("vmscan: do not unconditionally treat zones that fail zone_reclaim() as full") changed the return value of node_reclaim(). The original return value 0 means NODE_RECLAIM_SOME after this commit. While the return value of node_reclaim() when CONFIG_NUMA is n is not changed. This will leads to call zone_watermark_ok() again. This patch fixes the return value by adjusting to NODE_RECLAIM_NOSCAN. Since node_reclaim() is only called in page_alloc.c, move it to mm/internal.h. Link: http://lkml.kernel.org/r/20181113080436.22078-1-richard.weiyang@gmail.comSigned-off-by:
Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by:
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Arun KS authored
Now that totalram_pages and managed_pages are atomic varibles, no need of managed_page_count spinlock. The lock had really a weak consistency guarantee. It hasn't been used for anything but the update but no reader actually cares about all the values being updated to be in sync. Link: http://lkml.kernel.org/r/1542090790-21750-5-git-send-email-arunks@codeaurora.orgSigned-off-by:
Arun KS <arunks@codeaurora.org> Reviewed-by:
Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Acked-by:
Pavel Tatashin <pasha.tatashin@soleen.com> Signed-off-by:
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Arun KS authored
totalram_pages and totalhigh_pages are made static inline function. Main motivation was that managed_page_count_lock handling was complicating things. It was discussed in length here, https://lore.kernel.org/patchwork/patch/995739/#1181785 So it seemes better to remove the lock and convert variables to atomic, with preventing poteintial store-to-read tearing as a bonus. [akpm@linux-foundation.org: coding style fixes] Link: http://lkml.kernel.org/r/1542090790-21750-4-git-send-email-arunks@codeaurora.orgSigned-off-by:
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Arun KS authored
totalram_pages, zone->managed_pages and totalhigh_pages updates are protected by managed_page_count_lock, but readers never care about it. Convert these variables to atomic to avoid readers potentially seeing a store tear. This patch converts zone->managed_pages. Subsequent patches will convert totalram_panges, totalhigh_pages and eventually managed_page_count_lock will be removed. Main motivation was that managed_page_count_lock handling was complicating things. It was discussed in length here, https://lore.kernel.org/patchwork/patch/995739/#1181785 So it seemes better to remove the lock and convert variables to atomic, with preventing poteintial store-to-read tearing as a bonus. Link: http://lkml.kernel.org/r/1542090790-21750-3-git-send-email-arunks@codeaurora.orgSigned-off-by:
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Arun KS authored
Patch series "mm: convert totalram_pages, totalhigh_pages and managed pages to atomic", v5. This series converts totalram_pages, totalhigh_pages and zone->managed_pages to atomic variables. totalram_pages, zone->managed_pages and totalhigh_pages updates are protected by managed_page_count_lock, but readers never care about it. Convert these variables to atomic to avoid readers potentially seeing a store tear. Main motivation was that managed_page_count_lock handling was complicating things. It was discussed in length here, https://lore.kernel.org/patchwork/patch/995739/#1181785 It seemes better to remove the lock and convert variables to atomic. With the change, preventing poteintial store-to-read tearing comes as a bonus. This patch (of 4): This is in preparation to a later patch which converts totalram_pages and zone->managed_pages to atomic variables. Please note that re-reading the value might lead to a different value and as such it could lead to unexpected behavior. There are no known bugs as a result of the current code but it is better to prevent from them in principle. Link: http://lkml.kernel.org/r/1542090790-21750-2-git-send-email-arunks@codeaurora.orgSigned-off-by:
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Wei Yang authored
per_cpu_pageset is cleared by memset, it is not necessary to reset it again. Link: http://lkml.kernel.org/r/20181021023920.5501-1-richard.weiyang@gmail.comSigned-off-by:
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Michal Hocko authored
Per-cpu numa_node provides a default node for each possible cpu. The association gets initialized during the boot when the architecture specific code explores cpu->NUMA affinity. When the whole NUMA node is removed though we are clearing this association try_offline_node check_and_unmap_cpu_on_node unmap_cpu_on_node numa_clear_node numa_set_node(cpu, NUMA_NO_NODE) This means that whoever calls cpu_to_node for a cpu associated with such a node will get NUMA_NO_NODE. This is problematic for two reasons. First it is fragile because __alloc_pages_node would simply blow up on an out-of-bound access. We have encountered this when loading kvm module BUG: unable to handle kernel paging request at 00000000000021c0 IP: __alloc_pages_nodemask+0x93/0xb70 PGD 800000ffe853e067 PUD 7336bbc067 PMD 0 Oops: 0000 [#1] SMP [...] CPU: 88 PID: 1223749 Comm: modprobe Tainted: G W 4.4.156-94.64-default #1 RIP: __alloc_pages_nodemask+0x93/0xb70 RSP: 0018:ffff887354493b40 EFLAGS: 00010202 RAX: 00000000000021c0 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00000000014000c0 RBP: 00000000014000c0 R08: ffffffffffffffff R09: 0000000000000000 R10: ffff88fffc89e790 R11: 0000000000014000 R12: 0000000000000101 R13: ffffffffa0772cd4 R14: ffffffffa0769ac0 R15: 0000000000000000 FS: 00007fdf2f2f1700(0000) GS:ffff88fffc880000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000021c0 CR3: 00000077205ee000 CR4: 0000000000360670 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: alloc_vmcs_cpu+0x3d/0x90 [kvm_intel] hardware_setup+0x781/0x849 [kvm_intel] kvm_arch_hardware_setup+0x28/0x190 [kvm] kvm_init+0x7c/0x2d0 [kvm] vmx_init+0x1e/0x32c [kvm_intel] do_one_initcall+0xca/0x1f0 do_init_module+0x5a/0x1d7 load_module+0x1393/0x1c90 SYSC_finit_module+0x70/0xa0 entry_SYSCALL_64_fastpath+0x1e/0xb7 DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x1e/0xb7 on an older kernel but the code is basically the same in the current Linus tree as well. alloc_vmcs_cpu could use alloc_pages_nodemask which would recognize NUMA_NO_NODE and use alloc_pages_node which would translate it to numa_mem_id but that is wrong as well because it would use a cpu affinity of the local CPU which might be quite far from the original node. It is also reasonable to expect that cpu_to_node will provide a sane value and there might be many more callers like that. The second problem is that __register_one_node relies on cpu_to_node to properly associate cpus back to the node when it is onlined. We do not want to lose that link as there is no arch independent way to get it from the early boot time AFAICS. Drop the whole check_and_unmap_cpu_on_node machinery and keep the association to fix both issues. The NODE_DATA(nid) is not deallocated so it will stay in place and if anybody wants to allocate from that node then a fallback node will be used. Thanks to Vlastimil Babka for his live system debugging skills that helped debugging the issue. Link: http://lkml.kernel.org/r/20181108100413.966-1-mhocko@kernel.org Fixes: e13fe869 ("cpu-hotplug,memory-hotplug: clear cpu_to_node() when offlining the node") Signed-off-by:Miroslav Benes <mbenes@suse.cz> Acked-by:
Anshuman Khandual <anshuman.khandual@arm.com> Signed-off-by:
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Yangtao Li authored
We should get rid of this function. It no longer serves its purpose. This is a historical artifact from 2005 where do_brk was called outside of the core mm. We do have a proper abstraction in vm_brk_flags and that one does the locking properly so there is no need to use this function. Link: http://lkml.kernel.org/r/20181108174856.10811-1-tiny.windzz@gmail.comSigned-off-by:
Yangtao Li <tiny.windzz@gmail.com> Acked-by:
David Rientjes <rientjes@google.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Woodhouse <dwmw2@infradead.org> Signed-off-by:
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Timofey Titovets authored
Replace jhash2 with xxhash. Perf numbers: Intel(R) Xeon(R) CPU E5-2420 v2 @ 2.20GHz ksm: crc32c hash() 12081 MB/s ksm: xxh64 hash() 8770 MB/s ksm: xxh32 hash() 4529 MB/s ksm: jhash2 hash() 1569 MB/s Sioh Lee did some testing: crc32c_intel: 1084.10ns crc32c (no hardware acceleration): 7012.51ns xxhash32: 2227.75ns xxhash64: 1413.16ns jhash2: 5128.30ns As jhash2 always will be slower (for data size like PAGE_SIZE). Don't use it in ksm at all. Use only xxhash for now, because for using crc32c, cryptoapi must be initialized first - that requires some tricky solution to work well in all situations. Link: http://lkml.kernel.org/r/20181023182554.23464-3-nefelim4ag@gmail.comSigned-off-by:
Timofey Titovets <nefelim4ag@gmail.com> Signed-off-by:
leesioh <solee@os.korea.ac.kr> Reviewed-by:
Pavel Tatashin <pavel.tatashin@microsoft.com> Reviewed-by:
Mike Rapoport <rppt@linux.vnet.ibm.com> Reviewed-by:
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Timofey Titovets authored
Patch series "Currently used jhash are slow enough and replace it allow as to make KSM", v8. Apeed (in kernel): ksm: crc32c hash() 12081 MB/s ksm: xxh64 hash() 8770 MB/s ksm: xxh32 hash() 4529 MB/s ksm: jhash2 hash() 1569 MB/s Sioh Lee's testing (copy from other mail): Test platform: openstack cloud platform (NEWTON version) Experiment node: openstack based cloud compute node (CPU: xeon E5-2620 v3, memory 64gb) VM: (2 VCPU, RAM 4GB, DISK 20GB) * 4 Linux kernel: 4.14 (latest version) KSM setup - sleep_millisecs: 200ms, pages_to_scan: 200 Experiment process: Firstly, we turn off KSM and launch 4 VMs. Then we turn on the KSM and measure the checksum computation time until full_scans become two. The experimental results (the experimental value is the average of the measured values) crc32c_intel: 1084.10ns crc32c (no hardware acceleration): 7012.51ns xxhash32: 2227.75ns xxhash64: 1413.16ns jhash2: 5128.30ns In summary, the result shows that crc32c_intel has advantages over all of the hash function used in the experiment. (decreased by 84.54% compared to crc32c, 78.86% compared to jhash2, 51.33% xxhash32, 23.28% compared to xxhash64) the results are similar to those of Timofey. But, use only xxhash for now, because for using crc32c, cryptoapi must be initialized first - that require some tricky solution to work good in all situations. So: - First patch implement compile time pickup of fastest implementation of xxhash for target platform. - The second patch replaces jhash2 with xxhash This patch (of 2): xxh32() - fast on both 32/64-bit platforms xxh64() - fast only on 64-bit platform Create xxhash() which will pick up the fastest version at compile time. Link: http://lkml.kernel.org/r/20181023182554.23464-2-nefelim4ag@gmail.comSigned-off-by: -
Michal Hocko authored
Heiko has complained that his log is swamped by warnings from has_unmovable_pages [ 20.536664] page dumped because: has_unmovable_pages [ 20.536792] page:000003d081ff4080 count:1 mapcount:0 mapping:000000008ff88600 index:0x0 compound_mapcount: 0 [ 20.536794] flags: 0x3fffe0000010200(slab|head) [ 20.536795] raw: 03fffe0000010200 0000000000000100 0000000000000200 000000008ff88600 [ 20.536796] raw: 0000000000000000 0020004100000000 ffffffff00000001 0000000000000000 [ 20.536797] page dumped because: has_unmovable_pages [ 20.536814] page:000003d0823b0000 count:1 mapcount:0 mapping:0000000000000000 index:0x0 [ 20.536815] flags: 0x7fffe0000000000() [ 20.536817] raw: 07fffe0000000000 0000000000000100 0000000000000200 0000000000000000 [ 20.536818] raw: 0000000000000000 0000000000000000 ffffffff00000001 0000000000000000 which are not triggered by the memory hotplug but rather CMA allocator. The original idea behind dumping the page state for all call paths was that these messages will be helpful debugging failures. From the above it seems that this is not the case for the CMA path because we are lacking much more context. E.g the second reported page might be a CMA allocated page. It is still interesting to see a slab page in the CMA area but it is hard to tell whether this is bug from the above output alone. Address this issue by dumping the page state only on request. Both start_isolate_page_range and has_unmovable_pages already have an argument to ignore hwpoison pages so make this argument more generic and turn it into flags and allow callers to combine non-default modes into a mask. While we are at it, has_unmovable_pages call from is_pageblock_removable_nolock (sysfs removable file) is questionable to report the failure so drop it from there as well. Link: http://lkml.kernel.org/r/20181218092802.31429-1-mhocko@kernel.orgSigned-off-by:
Heiko Carstens <heiko.carstens@de.ibm.com> Reviewed-by:
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Michal Hocko authored
There is only very limited information printed when the memory offlining fails: [ 1984.506184] rac1 kernel: memory offlining [mem 0x82600000000-0x8267fffffff] failed due to signal backoff This tells us that the failure is triggered by the userspace intervention but it doesn't tell us much more about the underlying reason. It might be that the page migration failes repeatedly and the userspace timeout expires and send a signal or it might be some of the earlier steps (isolation, memory notifier) takes too long. If the migration failes then it would be really helpful to see which page that and its state. The same applies to the isolation phase. If we fail to isolate a page from the allocator then knowing the state of the page would be helpful as well. Dump the page state that fails to get isolated or migrated. This will tell us more about the failure and what to focus on during debugging. [akpm@linux-foundation.org: add missing printk arg] [mhocko@suse.com: tweak dump_page() `reason' text] Link: http://lkml.kernel.org/r/20181116083020.20260-6-mhocko@kernel.org Link: http://lkml.kernel.org/r/20181107101830.17405-6-mhocko@kernel.orgSigned-off-by:
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Michal Hocko authored
The memory offlining failure reporting is inconsistent and insufficient. Some error paths simply do not report the failure to the log at all. When we do report there are no details about the reason of the failure and there are several of them which makes memory offlining failures hard to debug. Make sure that the memory offlining [mem %#010llx-%#010llx] failed message is printed for all failures and also provide a short textual reason for the failure e.g. [ 1984.506184] rac1 kernel: memory offlining [mem 0x82600000000-0x8267fffffff] failed due to signal backoff this tells us that the offlining has failed because of a signal pending aka user intervention. [akpm@linux-foundation.org: tweak messages a bit] Link: http://lkml.kernel.org/r/20181107101830.17405-5-mhocko@kernel.orgSigned-off-by:
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Michal Hocko authored
This function is never called from a context which would provide misaligned pfn range so drop the pointless check. Link: http://lkml.kernel.org/r/20181107101830.17405-4-mhocko@kernel.orgSigned-off-by:
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Michal Hocko authored
__dump_page messages use KERN_EMERG resp. KERN_ALERT loglevel (this is the case since 2004). Most callers of this function are really detecting a critical page state and BUG right after. On the other hand the function is called also from contexts which just want to inform about the page state and those would rather not disrupt logs that much (e.g. some systems route these messages to the normal console). Reduce the loglevel to KERN_WARNING to make dump_page easier to reuse for other contexts while those messages will still make it to the kernel log in most setups. Even if the loglevel setup filters warnings away those paths that are really critical already print the more targeted error or panic and that should make it to the kernel log. [mhocko@kernel.org: fix __dump_page()] Link: http://lkml.kernel.org/r/20181212142540.GA7378@dhcp22.suse.cz [akpm@linux-foundation.org: s/KERN_WARN/KERN_WARNING/, per Michal] Link: http://lkml.kernel.org/r/20181107101830.17405-3-mhocko@kernel.orgSigned-off-by:
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Michal Hocko authored
I have been promissing to improve memory offlining failures debugging for quite some time. As things stand now we get only very limited information in the kernel log when the offlining fails. It is usually only [ 1984.506184] rac1 kernel: memory offlining [mem 0x82600000000-0x8267fffffff] failed with no further details. We do not know what exactly fails and for what reason. Whenever I was forced to debug such a failure I've always had to do a debugging patch to tell me more. We can enable some tracepoints but it would be much better to get a better picture without using them. This patch series does 2 things. The first one is to make dump_page more usable by printing more information about the mapping patch 1. Then it reduces the log level from emerg to warning so that this function is usable from less critical context patch 2. Then I have added more detailed information about the offlining failure patch 4 and finally add dump_page to isolation and offlining migration paths. Patch 3 is a trivial cleanup. This patch (of 6): __dump_page prints the mapping pointer but that is quite unhelpful for many reports because the pointer itself only helps to distinguish anon/ksm mappings from other ones (because of lowest bits set). Sometimes it would be much more helpful to know what kind of mapping that is actually and if we know this is a file mapping then also try to resolve the dentry name. [dan.carpenter@oracle.com: fix a width vs precision bug in printk] Link: http://lkml.kernel.org/r/20181123072135.gqvblm2vdujbvfjs@kili.mountain [mhocko@kernel.org: use %dp to print dentry] Link: http://lkml.kernel.org/r/20181125080834.GB12455@dhcp22.suse.cz Link: http://lkml.kernel.org/r/20181107101830.17405-2-mhocko@kernel.orgSigned-off-by:
William Kucharski <william.kucharski@oracle.com> Cc: Oscar Salvador <OSalvador@suse.com> Cc: Baoquan He <bhe@redhat.com> Cc: Oscar Salvador <osalvador@suse.de> Signed-off-by:
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Gao Xiang authored
It's a trivial simplification for get_next_ra_size() and clear enough for humans to understand. It also fixes potential overflow if ra->size(< ra_pages) is too large. Link: http://lkml.kernel.org/r/1540707206-19649-1-git-send-email-hsiangkao@aol.comSigned-off-by:
Gao Xiang <hsiangkao@aol.com> Reviewed-by:
Fengguang Wu <fengguang.wu@intel.com> Reviewed-by:
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Anders Roxell authored
This happened while running in qemu-system-aarch64, the AMBA PL011 UART driver when enabling CONFIG_DEBUG_TEST_DRIVER_REMOVE. arch_initcall(pl011_init) came before subsys_initcall(default_bdi_init), devtmpfs' handle_remove() crashes because the reference count is a NULL pointer only because wb->bdi hasn't been initialized yet. Rework so that wb_put have an extra check if wb->bdi before decrement wb->refcnt and also add a WARN_ON_ONCE to get a warning if it happens again in other drivers. Link: http://lkml.kernel.org/r/20181030113545.30999-2-anders.roxell@linaro.org Fixes: 52ebea74 ("writeback: make backing_dev_info host cgroup-specific bdi_writebacks") Signed-off-by:
Arnd Bergmann <arnd@arndb.de> Signed-off-by:
Anders Roxell <anders.roxell@linaro.org> Co-developed-by:
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Sean Christopherson authored
Contrary to its name, mmu_notifier_synchronize() does not synchronize the notifier's SRCU instance, but rather waits for RCU callbacks to finish. i.e. it invokes rcu_barrier(). The RCU documentation is quite clear on this matter, explicitly calling out that rcu_barrier() does not imply synchronize_rcu(). As there are no callers of mmu_notifier_synchronize() and it's unclear whether any user of mmu_notifier_call_srcu() will ever want to barrier on their callbacks, simply remove the function. Link: http://lkml.kernel.org/r/20181106134705.14197-1-sean.j.christopherson@intel.comSigned-off-by:
Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by:
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Balbir Singh authored
In hot remove, we try to clear poisoned pages, but a small optimization to check if num_poisoned_pages is 0 helps remove the iteration through nr_pages. [akpm@linux-foundation.org: tweak comment text] Link: http://lkml.kernel.org/r/20181102120001.4526-1-bsingharora@gmail.comSigned-off-by:
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by:
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Miles Chen authored
The (root-only) page owner read might allocate a large size of memory with a large read count. Allocation fails can easily occur when doing high order allocations. Clamp buffer size to PAGE_SIZE to avoid arbitrary size allocation and avoid allocation fails due to high order allocation. [akpm@linux-foundation.org: use min_t()] Link: http://lkml.kernel.org/r/1541091607-27402-1-git-send-email-miles.chen@mediatek.comSigned-off-by:
Miles Chen <miles.chen@mediatek.com> Acked-by:
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