- 06 Mar, 2019 40 commits
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Mel Gorman authored
When compaction is finishing, it uses a flag to ensure the pageblock is complete but it makes sense to always complete migration of a pageblock. Minimally, skip information is based on a pageblock and partially scanned pageblocks may incur more scanning in the future. The pageblock skip handling also becomes more strict later in the series and the hint is more useful if a complete pageblock was always scanned. The potentially impacts latency as more scanning is done but it's not a consistent win or loss as the scanning is not always a high percentage of the pageblock and sometimes it is offset by future reductions in scanning. Hence, the results are not presented this time due to a misleading mix of gains/losses without any clear pattern. However, full scanning of the pageblock is important for later patches. Link: http://lkml.kernel.org/r/20190118175136.31341-8-mgorman@techsingularity.netSigned-off-by:
Mel Gorman <mgorman@techsingularity.net> Acked-by:
Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: David Rientjes <rientjes@google.com> Cc: YueHaibing <yuehaibing@huawei.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Mel Gorman authored
Pages with no migration handler use a fallback handler which sometimes works and sometimes persistently retries. A historical example was blockdev pages but there are others such as odd refcounting when page->private is used. These are retried multiple times which is wasteful during compaction so this patch will fail migration faster unless the caller specifies MIGRATE_SYNC. This is not expected to help THP allocation success rates but it did reduce latencies very slightly in some cases. 1-socket thpfioscale 4.20.0 4.20.0 noreserved-v2r15 failfast-v2r15 Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%* Amean fault-both-3 3839.67 ( 0.00%) 3833.72 ( 0.15%) Amean fault-both-5 5177.47 ( 0.00%) 4967.15 ( 4.06%) Amean fault-both-7 7245.03 ( 0.00%) 7139.19 ( 1.46%) Amean fault-both-12 11534.89 ( 0.00%) 11326.30 ( 1.81%) Amean fault-both-18 16241.10 ( 0.00%) 16270.70 ( -0.18%) Amean fault-both-24 19075.91 ( 0.00%) 19839.65 ( -4.00%) Amean fault-both-30 22712.11 ( 0.00%) 21707.05 ( 4.43%) Amean fault-both-32 21692.92 ( 0.00%) 21968.16 ( -1.27%) The 2-socket results are not materially different. Scan rates are similar as expected. Link: http://lkml.kernel.org/r/20190118175136.31341-7-mgorman@techsingularity.netSigned-off-by: -
Mel Gorman authored
It's non-obvious that high-order free pages are split into order-0 pages from the function name. Fix it. Link: http://lkml.kernel.org/r/20190118175136.31341-6-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
A zone parameter is passed into a number of top-level compaction functions despite the fact that it's already in compact_control. This is harmless but it did need an audit to check if zone actually ever changes meaningfully. This patches removes the parameter in a number of top-level functions. The change could be much deeper but this was enough to briefly clarify the flow. No functional change. Link: http://lkml.kernel.org/r/20190118175136.31341-5-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
The last_migrated_pfn field is a bit dubious as to whether it really helps but either way, the information from it can be inferred without increasing the size of compact_control so remove the field. Link: http://lkml.kernel.org/r/20190118175136.31341-4-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
compact_control spans two cache lines with write-intensive lines on both. Rearrange so the most write-intensive fields are in the same cache line. This has a negligible impact on the overall performance of compaction and is more a tidying exercise than anything. Link: http://lkml.kernel.org/r/20190118175136.31341-3-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
Patch series "Increase success rates and reduce latency of compaction", v3. This series reduces scan rates and success rates of compaction, primarily by using the free lists to shorten scans, better controlling of skip information and whether multiple scanners can target the same block and capturing pageblocks before being stolen by parallel requests. The series is based on mmotm from January 9th, 2019 with the previous compaction series reverted. I'm mostly using thpscale to measure the impact of the series. The benchmark creates a large file, maps it, faults it, punches holes in the mapping so that the virtual address space is fragmented and then tries to allocate THP. It re-executes for different numbers of threads. From a fragmentation perspective, the workload is relatively benign but it does stress compaction. The overall impact on latencies for a 1-socket machine is baseline patches Amean fault-both-3 3832.09 ( 0.00%) 2748.56 * 28.28%* Amean fault-both-5 4933.06 ( 0.00%) 4255.52 ( 13.73%) Amean fault-both-7 7017.75 ( 0.00%) 6586.93 ( 6.14%) Amean fault-both-12 11610.51 ( 0.00%) 9162.34 * 21.09%* Amean fault-both-18 17055.85 ( 0.00%) 11530.06 * 32.40%* Amean fault-both-24 19306.27 ( 0.00%) 17956.13 ( 6.99%) Amean fault-both-30 22516.49 ( 0.00%) 15686.47 * 30.33%* Amean fault-both-32 23442.93 ( 0.00%) 16564.83 * 29.34%* The allocation success rates are much improved baseline patches Percentage huge-3 85.99 ( 0.00%) 97.96 ( 13.92%) Percentage huge-5 88.27 ( 0.00%) 96.87 ( 9.74%) Percentage huge-7 85.87 ( 0.00%) 94.53 ( 10.09%) Percentage huge-12 82.38 ( 0.00%) 98.44 ( 19.49%) Percentage huge-18 83.29 ( 0.00%) 99.14 ( 19.04%) Percentage huge-24 81.41 ( 0.00%) 97.35 ( 19.57%) Percentage huge-30 80.98 ( 0.00%) 98.05 ( 21.08%) Percentage huge-32 80.53 ( 0.00%) 97.06 ( 20.53%) That's a nearly perfect allocation success rate. The biggest impact is on the scan rates Compaction migrate scanned 55893379 19341254 Compaction free scanned 474739990 11903963 The number of pages scanned for migration was reduced by 65% and the free scanner was reduced by 97.5%. So much less work in exchange for lower latency and better success rates. The series was also evaluated using a workload that heavily fragments memory but the benefits there are also significant, albeit not presented. It was commented that we should be rethinking scanning entirely and to a large extent I agree. However, to achieve that you need a lot of this series in place first so it's best to make the linear scanners as best as possible before ripping them out. This patch (of 22): The isolate and migrate scanners should never isolate more than a pageblock of pages so unsigned int is sufficient saving 8 bytes on a 64-bit build. Link: http://lkml.kernel.org/r/20190118175136.31341-2-mgorman@techsingularity.netSigned-off-by:
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zhengbin authored
The 'end_byte' parameter of filemap_range_has_page is required to be inclusive, so follow the rule. Link: http://lkml.kernel.org/r/1548678679-18122-1-git-send-email-zhengbin13@huawei.com Fixes: 6be96d3a ("fs: return if direct I/O will trigger writeback") Signed-off-by:
zhengbin <zhengbin13@huawei.com> Reviewed-by:
Matthew Wilcox <willy@infradead.org> Acked-by:
Christoph Hellwig <hch@lst.de> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Amir Goldstein <amir73il@gmail.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Hou Tao <houtao1@huawei.com> Cc: zhangyi (F) <yi.zhang@huawei.com> Cc: Jan Kara <jack@suse.cz> Signed-off-by:
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Alexey Dobriyan authored
GFP_KERNEL is one of the most used constant but on archs like arm with fixed length instruction some constants are more equal than the others. Constants with tightly packed bits can be injected directly into instruction stream: 0: e3a00d33 mov r0, #3264 ; 0xcc0 Others require multiple instructions or even loading out of instruction stream: 0: e3a000c0 mov r0, #192 ; 0xc0 4: e3400060 movt r0, #96 ; 0x60 Shuffle GFP_* flags so that GFP_KERNEL/GFP_ATOMIC + __GFP_ZERO bits are close to each other. Savings on arm configs are ~0.1%. Link: http://lkml.kernel.org/r/20190109201838.GA9140@avx2Signed-off-by:
Alexey Dobriyan <adobriyan@gmail.com> Reviewed-by:
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Yang Shi authored
swap_vma_readahead()'s comment is missing, just add it. Link: http://lkml.kernel.org/r/1546543673-108536-2-git-send-email-yang.shi@linux.alibaba.comSigned-off-by:
Yang Shi <yang.shi@linux.alibaba.com> Reviewed-by:
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Yang Shi authored
Swap readahead would read in a few pages regardless if the underlying device is busy or not. It may incur long waiting time if the device is congested, and it may also exacerbate the congestion. Use inode_read_congested() to check if the underlying device is busy or not like what file page readahead does. Get inode from swap_info_struct. Although we can add inode information in swap_address_space (address_space->host), it may lead some unexpected side effect, i.e. it may break mapping_cap_account_dirty(). Using inode from swap_info_struct seems simple and good enough. Just does the check in vma_cluster_readahead() since swap_vma_readahead() is just used for non-rotational device which much less likely has congestion than traditional HDD. Although swap slots may be consecutive on swap partition, it still may be fragmented on swap file. This check would help to reduce excessive stall for such case. The test with page_fault1 of will-it-scale (sometimes tracing may just show runtest.py that is the wrapper script of page_fault1), which basically launches NR_CPU threads to generate 128MB anonymous pages for each thread, on my virtual machine with congested HDD shows long tail latency is reduced significantly. Without the patch page_fault1_thr-1490 [023] 129.311706: funcgraph_entry: #57377.796 us | do_swap_page(); page_fault1_thr-1490 [023] 129.369103: funcgraph_entry: 5.642us | do_swap_page(); page_fault1_thr-1490 [023] 129.369119: funcgraph_entry: #1289.592 us | do_swap_page(); page_fault1_thr-1490 [023] 129.370411: funcgraph_entry: 4.957us | do_swap_page(); page_fault1_thr-1490 [023] 129.370419: funcgraph_entry: 1.940us | do_swap_page(); page_fault1_thr-1490 [023] 129.378847: funcgraph_entry: #1411.385 us | do_swap_page(); page_fault1_thr-1490 [023] 129.380262: funcgraph_entry: 3.916us | do_swap_page(); page_fault1_thr-1490 [023] 129.380275: funcgraph_entry: #4287.751 us | do_swap_page(); With the patch runtest.py-1417 [020] 301.925911: funcgraph_entry: #9870.146 us | do_swap_page(); runtest.py-1417 [020] 301.935785: funcgraph_entry: 9.802us | do_swap_page(); runtest.py-1417 [020] 301.935799: funcgraph_entry: 3.551us | do_swap_page(); runtest.py-1417 [020] 301.935806: funcgraph_entry: 2.142us | do_swap_page(); runtest.py-1417 [020] 301.935853: funcgraph_entry: 6.938us | do_swap_page(); runtest.py-1417 [020] 301.935864: funcgraph_entry: 3.765us | do_swap_page(); runtest.py-1417 [020] 301.935871: funcgraph_entry: 3.600us | do_swap_page(); runtest.py-1417 [020] 301.935878: funcgraph_entry: 7.202us | do_swap_page(); [akpm@linux-foundation.org: code cleanup] [yang.shi@linux.alibaba.com: add comment] Link: http://lkml.kernel.org/r/bbc7bda7-62d0-df1a-23ef-d369e865bdca@linux.alibaba.com Link: http://lkml.kernel.org/r/1546543673-108536-1-git-send-email-yang.shi@linux.alibaba.comSigned-off-by:Tim Chen <tim.c.chen@intel.com> Reviewed-by:
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Matthew Wilcox authored
After we establish a reference on the page, we check the pointer continues to be in the correct position in i_pages. Checking page->index afterwards is unnecessary; if it were to change, then the pointer to it from the page cache would also move. The check used to be done before grabbing a reference on the page which was racy (see commit 9cbb4cb2 ("mm: find_get_pages_contig fixlet")), but nobody noticed that moving the check after grabbing the reference was redundant. Link: http://lkml.kernel.org/r/20190107200224.13260-1-willy@infradead.orgSigned-off-by:
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Gustavo A. R. Silva authored
One of the more common cases of allocation size calculations is finding the size of a structure that has a zero-sized array at the end, along with memory for some number of elements for that array. For example: struct foo { int stuff; void *entry[]; }; instance = kmalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL); Instead of leaving these open-coded and prone to type mistakes, we can now use the new struct_size() helper: instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL); This code was detected with the help of Coccinelle. Link: http://lkml.kernel.org/r/20190104183726.GA6374@embeddedorSigned-off-by:Gustavo A. R. Silva <gustavo@embeddedor.com> Acked-by:
Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by:
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Wei Yang authored
In the current implementation, there are two places to isolate a range of page: __offline_pages() and alloc_contig_range(). During this procedure, it will drain pages on pcp list. Below is a brief call flow: __offline_pages()/alloc_contig_range() start_isolate_page_range() set_migratetype_isolate() drain_all_pages() drain_all_pages() <--- A This snippet shows the current logic is isolate and drain pcp list for each pageblock and drain pcp list again for the whole range. start_isolate_page_range is responsible for isolating the given pfn range. One part of that job is to make sure that also pages that are on the allocator pcp lists are properly isolated. Otherwise they could be reused and the range wouldn't be completely isolated until the memory is freed back. While there is no strict guarantee here because pages might get allocated at any time before drain_all_pages is called there doesn't seem to be any strong demand for such a guarantee. In any case, draining is already done at the isolation level and there is no need to do it again later by start_isolate_page_range callers (memory hotplug and CMA allocator currently). Therefore remove pointless draining in existing callers to make the code more clear and functionally correct. [mhocko@suse.com: provide a clearer changelog for the last two paragraphs] Link: http://lkml.kernel.org/r/20190105233141.2329-1-richard.weiyang@gmail.comSigned-off-by:Wei Yang <richard.weiyang@gmail.com> Acked-by:
David Hildenbrand <david@redhat.com> Reviewed-by:
Oscar Salvador <osalvador@suse.de> Signed-off-by:
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Anshuman Khandual authored
Let arm64 subscribe to the previously added framework in which architecture can inform whether a given huge page size is supported for migration. This just overrides the default function arch_hugetlb_migration_supported() and enables migration for all possible HugeTLB page sizes on arm64. With this, HugeTLB migration support on arm64 now covers all possible HugeTLB options. CONT PTE PMD CONT PMD PUD -------- --- -------- --- 4K: 64K 2M 32M 1G 16K: 2M 32M 1G 64K: 2M 512M 16G Link: http://lkml.kernel.org/r/1545121450-1663-6-git-send-email-anshuman.khandual@arm.comSigned-off-by:Anshuman Khandual <anshuman.khandual@arm.com> Reviewed-by:
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reviewed-by:
Steve Capper <steve.capper@arm.com> Acked-by:
Catalin Marinas <catalin.marinas@arm.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by:
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Anshuman Khandual authored
Let arm64 subscribe to generic HugeTLB page migration framework. Right now this only works on the following PMD and PUD level HugeTLB page sizes with various kernel base page size combinations. CONT PTE PMD CONT PMD PUD -------- --- -------- --- 4K: NA 2M NA 1G 16K: NA 32M NA 64K: NA 512M NA Link: http://lkml.kernel.org/r/1545121450-1663-5-git-send-email-anshuman.khandual@arm.comSigned-off-by: -
Anshuman Khandual authored
Architectures like arm64 have HugeTLB page sizes which are different than generic sizes at PMD, PUD, PGD level and implemented via contiguous bits. At present these special size HugeTLB pages cannot be identified through macros like (PMD|PUD|PGDIR)_SHIFT and hence chosen not be migrated. Enabling migration support for these special HugeTLB page sizes along with the generic ones (PMD|PUD|PGD) would require identifying all of them on a given platform. A platform specific hook can precisely enumerate all huge page sizes supported for migration. Instead of comparing against standard huge page orders let hugetlb_migration_support() function call a platform hook arch_hugetlb_migration_support(). Default definition for the platform hook maintains existing semantics which checks standard huge page order. But an architecture can choose to override the default and provide support for a comprehensive set of huge page sizes. Link: http://lkml.kernel.org/r/1545121450-1663-4-git-send-email-anshuman.khandual@arm.comSigned-off-by:
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Anshuman Khandual authored
Architectures like arm64 have PUD level HugeTLB pages for certain configs (1GB huge page is PUD based on ARM64_4K_PAGES base page size) that can be enabled for migration. It can be achieved through checking for PUD_SHIFT order based HugeTLB pages during migration. Link: http://lkml.kernel.org/r/1545121450-1663-3-git-send-email-anshuman.khandual@arm.comSigned-off-by:
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Anshuman Khandual authored
Patch series "arm64/mm: Enable HugeTLB migration", v4. This patch series enables HugeTLB migration support for all supported huge page sizes at all levels including contiguous bit implementation. Following HugeTLB migration support matrix has been enabled with this patch series. All permutations have been tested except for the 16GB. CONT PTE PMD CONT PMD PUD -------- --- -------- --- 4K: 64K 2M 32M 1G 16K: 2M 32M 1G 64K: 2M 512M 16G First the series adds migration support for PUD based huge pages. It then adds a platform specific hook to query an architecture if a given huge page size is supported for migration while also providing a default fallback option preserving the existing semantics which just checks for (PMD|PUD|PGDIR)_SHIFT macros. The last two patches enables HugeTLB migration on arm64 and subscribe to this new platform specific hook by defining an override. The second patch differentiates between movability and migratability aspects of huge pages and implements hugepage_movable_supported() which can then be used during allocation to decide whether to place the huge page in movable zone or not. This patch (of 5): During huge page allocation it's migratability is checked to determine if it should be placed under movable zones with GFP_HIGHUSER_MOVABLE. But the movability aspect of the huge page could depend on other factors than just migratability. Movability in itself is a distinct property which should not be tied with migratability alone. This differentiates these two and implements an enhanced movability check which also considers huge page size to determine if it is feasible to be placed under a movable zone. At present it just checks for gigantic pages but going forward it can incorporate other enhanced checks. Link: http://lkml.kernel.org/r/1545121450-1663-2-git-send-email-anshuman.khandual@arm.comSigned-off-by:Michal Hocko <mhocko@kernel.org> Acked-by:
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Matthew Wilcox authored
sysctl_extfrag_handler() neglects to propagate the return value from proc_dointvec_minmax() to its caller. It's a wrapper that doesn't need to exist, so just use proc_dointvec_minmax() directly. Link: http://lkml.kernel.org/r/20190104032557.3056-1-willy@infradead.orgSigned-off-by:
Aditya Pakki <pakki001@umn.edu> Acked-by:
Randy Dunlap <rdunlap@infradead.org> Signed-off-by:
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Uladzislau Rezki (Sony) authored
Add the test script for the kernel test driver to analyse vmalloc allocator for benchmarking and stressing purposes. It is just a kernel module loader. You can specify and pass different parameters in order to investigate allocations behaviour. See "usage" output for more details. Also add basic vmalloc smoke test to the "run_vmtests" suite. Link: http://lkml.kernel.org/r/20190103142108.20744-4-urezki@gmail.comSigned-off-by:
Uladzislau Rezki (Sony) <urezki@gmail.com> Reviewed-by:
Shuah Khan <shuah@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
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Uladzislau Rezki (Sony) authored
This adds a new kernel module for analysis of vmalloc allocator. It is only enabled as a module. There are two main reasons this module should be used for: performance evaluation and stressing of vmalloc subsystem. It consists of several test cases. As of now there are 8. The module has five parameters we can specify to change its the behaviour. 1) run_test_mask - set of tests to be run id: 1, name: fix_size_alloc_test id: 2, name: full_fit_alloc_test id: 4, name: long_busy_list_alloc_test id: 8, name: random_size_alloc_test id: 16, name: fix_align_alloc_test id: 32, name: random_size_align_alloc_test id: 64, name: align_shift_alloc_test id: 128, name: pcpu_alloc_test By default all tests are in run test mask. If you want to select some specific tests it is possible to pass the mask. For example for first, second and fourth tests we go 11 value. 2) test_repeat_count - how many times each test should be repeated By default it is one time per test. It is possible to pass any number. As high the value is the test duration gets increased. 3) test_loop_count - internal test loop counter. By default it is set to 1000000. 4) single_cpu_test - use one CPU to run the tests By default this parameter is set to false. It means that all online CPUs execute tests. By setting it to 1, the tests are executed by first online CPU only. 5) sequential_test_order - run tests in sequential order By default this parameter is set to false. It means that before running tests the order is shuffled. It is possible to make it sequential, just set it to 1. Performance analysis: In order to evaluate performance of vmalloc allocations, usually it makes sense to use only one CPU that runs tests, use sequential order, number of repeat tests can be different as well as set of test mask. For example if we want to run all tests, to use one CPU and repeat each test 3 times. Insert the module passing following parameters: single_cpu_test=1 sequential_test_order=1 test_repeat_count=3 with following output: <snip> Summary: fix_size_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 901177 usec Summary: full_fit_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 1039341 usec Summary: long_busy_list_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 11775763 usec Summary: random_size_alloc_test passed 3: failed: 0 repeat: 3 loops: 1000000 avg: 6081992 usec Summary: fix_align_alloc_test passed: 3 failed: 0 repeat: 3, loops: 1000000 avg: 2003712 usec Summary: random_size_align_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 2895689 usec Summary: align_shift_alloc_test passed: 0 failed: 3 repeat: 3 loops: 1000000 avg: 573 usec Summary: pcpu_alloc_test passed: 3 failed: 0 repeat: 3 loops: 1000000 avg: 95802 usec All test took CPU0=192945605995 cycles <snip> The align_shift_alloc_test is expected to be failed. Stressing: In order to stress the vmalloc subsystem we run all available test cases on all available CPUs simultaneously. In order to prevent constant behaviour pattern, the test cases array is shuffled by default to randomize the order of test execution. For example if we want to run all tests(default), use all online CPUs(default) with shuffled order(default) and to repeat each test 30 times. The command would be like: modprobe vmalloc_test test_repeat_count=30 Expected results are the system is alive, there are no any BUG_ONs or Kernel Panics the tests are completed, no memory leaks. [urezki@gmail.com: fix 32-bit builds] Link: http://lkml.kernel.org/r/20190106214839.ffvjvmrn52uqog7k@pc636 [urezki@gmail.com: make CONFIG_TEST_VMALLOC depend on CONFIG_MMU] Link: http://lkml.kernel.org/r/20190219085441.s6bg2gpy4esny5vw@pc636 Link: http://lkml.kernel.org/r/20190103142108.20744-3-urezki@gmail.comSigned-off-by:
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Uladzislau Rezki (Sony) authored
Export __vmaloc_node_range() function if CONFIG_TEST_VMALLOC_MODULE is enabled. Some test cases in vmalloc test suite module require and make use of that function. Please note, that it is not supposed to be used for other purposes. We need it only for performance analysis, stressing and stability check of vmalloc allocator. Link: http://lkml.kernel.org/r/20190103142108.20744-2-urezki@gmail.comSigned-off-by:
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Roman Penyaev authored
vmalloc_user*() calls differ from normal vmalloc() only in that they set VM_USERMAP flags for the area. During the whole history of vmalloc.c changes now it is possible simply to pass VM_USERMAP flags directly to __vmalloc_node_range() call instead of finding the area (which obviously takes time) after the allocation. Link: http://lkml.kernel.org/r/20190103145954.16942-4-rpenyaev@suse.deSigned-off-by:
Roman Penyaev <rpenyaev@suse.de> Acked-by:
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Roman Penyaev authored
__vmalloc_area_node() calls vfree() on error path, which in turn calls kmemleak_free(), but area is not yet accounted by kmemleak_vmalloc(). Link: http://lkml.kernel.org/r/20190103145954.16942-3-rpenyaev@suse.deSigned-off-by:
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Roman Penyaev authored
When VM_NO_GUARD is not set area->size includes adjacent guard page, thus for correct size checking get_vm_area_size() should be used, but not area->size. This fixes possible kernel oops when userspace tries to mmap an area on 1 page bigger than was allocated by vmalloc_user() call: the size check inside remap_vmalloc_range_partial() accounts non-existing guard page also, so check successfully passes but vmalloc_to_page() returns NULL (guard page does not physically exist). The following code pattern example should trigger an oops: static int oops_mmap(struct file *file, struct vm_area_struct *vma) { void *mem; mem = vmalloc_user(4096); BUG_ON(!mem); /* Do not care about mem leak */ return remap_vmalloc_range(vma, mem, 0); } And userspace simply mmaps size + PAGE_SIZE: mmap(NULL, 8192, PROT_WRITE|PROT_READ, MAP_PRIVATE, fd, 0); Possible candidates for oops which do not have any explicit size checks: *** drivers/media/usb/stkwebcam/stk-webcam.c: v4l_stk_mmap[789] ret = remap_vmalloc_range(vma, sbuf->buffer, 0); Or the following one: *** drivers/video/fbdev/core/fbmem.c static int fb_mmap(struct file *file, struct vm_area_struct * vma) ... res = fb->fb_mmap(info, vma); Where fb_mmap callback calls remap_vmalloc_range() directly without any explicit checks: *** drivers/video/fbdev/vfb.c static int vfb_mmap(struct fb_info *info, struct vm_area_struct *vma) { return remap_vmalloc_range(vma, (void *)info->fix.smem_start, vma->vm_pgoff); } Link: http://lkml.kernel.org/r/20190103145954.16942-2-rpenyaev@suse.deSigned-off-by: -
Roman Penyaev authored
This patch repeats the original one from David S Miller: 2dca6999 ("mm, perf_event: Make vmalloc_user() align base kernel virtual address to SHMLBA") but for missed vmalloc_32_user() case, which also requires correct alignment of virtual address on kernel side to avoid D-caches aliases. A bit of copy-paste from original patch to recover in memory of what is all about: When a vmalloc'd area is mmap'd into userspace, some kind of co-ordination is necessary for this to work on platforms with cpu D-caches which can have aliases. Otherwise kernel side writes won't be seen properly in userspace and vice versa. If the kernel side mapping and the user side one have the same alignment, modulo SHMLBA, this can work as long as VM_SHARED is shared of VMA and for all current users this is true. VM_SHARED will force SHMLBA alignment of the user side mmap on platforms with D-cache aliasing matters. David S. Miller > What are the user-visible runtime effects of this change? In simple words: proper alignment avoids possible difference in data, seen by different virtual mapings: userspace and kernel in our case. I.e. userspace reads cache line A, kernel writes to cache line B. Both cache lines correspond to the same physical memory (thus aliases). So this should fix data corruption for archs with vivt and vipt caches, e.g. armv6. Personally I've never worked with this archs, I just spotted the strange difference in code: for one case we do alignment, for another - not. I have a strong feeling that David simply missed vmalloc_32_user() case. > > Is a -stable backport needed? No, I do not think so. The only one user of vmalloc_32_user() is virtual frame buffer device drivers/video/fbdev/vfb.c, which has in the description "The main use of this frame buffer device is testing and debugging the frame buffer subsystem. Do NOT enable it for normal systems!". And it seems to me that this vfb.c does not need 32bit addressable pages (vmalloc_32_user() case), because it is virtual device and should not care about things like dma32 zones, etc. Probably is better to clean the code and switch vfb.c from vmalloc_32_user() to vmalloc_user() case and wipe out vmalloc_32_user() from vmalloc.c completely. But I'm not very much sure that this is worth to do, that's so minor, so we can leave it as is. Link: http://lkml.kernel.org/r/20190108110944.23591-1-rpenyaev@suse.deSigned-off-by:
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Shakeel Butt authored
Move the memcg_kmem_enabled() checks into memcg kmem charge/uncharge functions, so, the users don't have to explicitly check that condition. This is purely code cleanup patch without any functional change. Only the order of checks in memcg_charge_slab() can potentially be changed but the functionally it will be same. This should not matter as memcg_charge_slab() is not in the hot path. Link: http://lkml.kernel.org/r/20190103161203.162375-1-shakeelb@google.comSigned-off-by:
Shakeel Butt <shakeelb@google.com> Acked-by:
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Wei Yang authored
There are two cases when put_cpu_partial() is invoked. * __slab_free * get_partial_node This patch just makes it cover these two cases. Link: http://lkml.kernel.org/r/20181025094437.18951-3-richard.weiyang@gmail.comSigned-off-by:Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by:
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Kirill Tkhai authored
Add an optimization for KSM pages almost in the same way that we have for ordinary anonymous pages. If there is a write fault in a page, which is mapped to an only pte, and it is not related to swap cache; the page may be reused without copying its content. [ Note that we do not consider PageSwapCache() pages at least for now, since we don't want to complicate __get_ksm_page(), which has nice optimization based on this (for the migration case). Currenly it is spinning on PageSwapCache() pages, waiting for when they have unfreezed counters (i.e., for the migration finish). But we don't want to make it also spinning on swap cache pages, which we try to reuse, since there is not a very high probability to reuse them. So, for now we do not consider PageSwapCache() pages at all. ] So in reuse_ksm_page() we check for 1) PageSwapCache() and 2) page_stable_node(), to skip a page, which KSM is currently trying to link to stable tree. Then we do page_ref_freeze() to prohibit KSM to merge one more page into the page, we are reusing. After that, nobody can refer to the reusing page: KSM skips !PageSwapCache() pages with zero refcount; and the protection against of all other participants is the same as for reused ordinary anon pages pte lock, page lock and mmap_sem. [akpm@linux-foundation.org: replace BUG_ON()s with WARN_ON()s] Link: http://lkml.kernel.org/r/154471491016.31352.1168978849911555609.stgit@localhost.localdomainSigned-off-by:
Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by:
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Stephen Rothwell authored
This replaces all open encodings in tools with NUMA_NO_NODE. Also linux/numa.h is now needed for the perf build. [sfr@canb.auug.org.au: fix for replace open encodings for NUMA_NO_NODE] Link: http://lkml.kernel.org/r/20190108131141.730e9c4f@canb.auug.org.au Link: http://lkml.kernel.org/r/1545127933-10711-3-git-send-email-anshuman.khandual@arm.comSigned-off-by:
Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by:
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Anshuman Khandual authored
Patch series "Replace all open encodings for NUMA_NO_NODE", v3. All these places for replacement were found by running the following grep patterns on the entire kernel code. Please let me know if this might have missed some instances. This might also have replaced some false positives. I will appreciate suggestions, inputs and review. 1. git grep "nid == -1" 2. git grep "node == -1" 3. git grep "nid = -1" 4. git grep "node = -1" This patch (of 2): At present there are multiple places where invalid node number is encoded as -1. Even though implicitly understood it is always better to have macros in there. Replace these open encodings for an invalid node number with the global macro NUMA_NO_NODE. This helps remove NUMA related assumptions like 'invalid node' from various places redirecting them to a common definition. Link: http://lkml.kernel.org/r/1545127933-10711-2-git-send-email-anshuman.khandual@arm.comSigned-off-by:
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Liviu Dudau authored
find_vmap_area() can return a NULL pointer and we're going to dereference it without checking it first. Use the existing find_vm_area() function which does exactly what we want and checks for the NULL pointer. Link: http://lkml.kernel.org/r/20181228171009.22269-1-liviu@dudau.co.uk Fixes: f3c01d2f ("mm: vmalloc: avoid racy handling of debugobjects in vunmap") Signed-off-by:
Liviu Dudau <liviu@dudau.co.uk> Reviewed-by:
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David Hildenbrand authored
The content of pages that are marked PG_offline is not of interest (e.g. inflated by a balloon driver), let's skip these pages. In saveable_highmem_page(), move the PageReserved() check to a new check along with the PageOffline() check to separate it from the swsusp checks. [david@redhat.com: v2] Link: http://lkml.kernel.org/r/20181122100627.5189-9-david@redhat.com Link: http://lkml.kernel.org/r/20181119101616.8901-9-david@redhat.comSigned-off-by:
Pavel Machek <pavel@ucw.cz> Acked-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Len Brown <len.brown@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Christian Hansen <chansen3@cisco.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Juergen Gross <jgross@suse.com> Cc: Julien Freche <jfreche@vmware.com> Cc: Kairui Song <kasong@redhat.com> Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Lianbo Jiang <lijiang@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Nadav Amit <namit@vmware.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Omar Sandoval <osandov@fb.com> Cc: Pankaj gupta <pagupta@redhat.com> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Xavier Deguillard <xdeguillard@vmware.com> Signed-off-by:
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David Hildenbrand authored
Let's use pfn_to_online_page() instead of pfn_to_page() when checking for saveable pages to not save/restore offline memory sections. Link: http://lkml.kernel.org/r/20181119101616.8901-8-david@redhat.comSigned-off-by:
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David Hildenbrand authored
Mark inflated and never onlined pages PG_offline, to tell the world that the content is stale and should not be dumped. [david@redhat.com: use vmballoon_page_in_frames more widely] Link: http://lkml.kernel.org/r/20181122100627.5189-7-david@redhat.com Link: http://lkml.kernel.org/r/20181119101616.8901-7-david@redhat.comSigned-off-by:
Nadav Amit <namit@vmware.com> Cc: Xavier Deguillard <xdeguillard@vmware.com> Cc: Nadav Amit <namit@vmware.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Julien Freche <jfreche@vmware.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Christian Hansen <chansen3@cisco.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Juergen Gross <jgross@suse.com> Cc: Kairui Song <kasong@redhat.com> Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Len Brown <len.brown@intel.com> Cc: Lianbo Jiang <lijiang@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Omar Sandoval <osandov@fb.com> Cc: Pankaj gupta <pagupta@redhat.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by:
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David Hildenbrand authored
Mark inflated and never onlined pages PG_offline, to tell the world that the content is stale and should not be dumped. Link: http://lkml.kernel.org/r/20181119101616.8901-6-david@redhat.comSigned-off-by:
Pankaj gupta <pagupta@redhat.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Kairui Song <kasong@redhat.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Christian Hansen <chansen3@cisco.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Juergen Gross <jgross@suse.com> Cc: Julien Freche <jfreche@vmware.com> Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Len Brown <len.brown@intel.com> Cc: Lianbo Jiang <lijiang@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Nadav Amit <namit@vmware.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Omar Sandoval <osandov@fb.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Xavier Deguillard <xdeguillard@vmware.com> Signed-off-by:
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David Hildenbrand authored
Mark inflated and never onlined pages PG_offline, to tell the world that the content is stale and should not be dumped. Link: http://lkml.kernel.org/r/20181119101616.8901-5-david@redhat.comSigned-off-by:
Juergen Gross <jgross@suse.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Christian Hansen <chansen3@cisco.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Julien Freche <jfreche@vmware.com> Cc: Kairui Song <kasong@redhat.com> Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Len Brown <len.brown@intel.com> Cc: Lianbo Jiang <lijiang@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Nadav Amit <namit@vmware.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Omar Sandoval <osandov@fb.com> Cc: Pankaj gupta <pagupta@redhat.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Xavier Deguillard <xdeguillard@vmware.com> Signed-off-by:
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David Hildenbrand authored
Right now, pages inflated as part of a balloon driver will be dumped by dump tools like makedumpfile. While XEN is able to check in the crash kernel whether a certain pfn is actuall backed by memory in the hypervisor (see xen_oldmem_pfn_is_ram) and optimize this case, dumps of other balloon inflated memory will essentially result in zero pages getting allocated by the hypervisor and the dump getting filled with this data. The allocation and reading of zero pages can directly be avoided if a dumping tool could know which pages only contain stale information not to be dumped. We now have PG_offline which can be (and already is by virtio-balloon) used for marking pages as logically offline. Follow up patches will make use of this flag also in other balloon implementations. Let's export PG_offline via PAGE_OFFLINE_MAPCOUNT_VALUE, so makedumpfile can directly skip pages that are logically offline and the content therefore stale. Please note that this is also helpful for a problem we were seeing under Hyper-V: Dumping logically offline memory (pages kept fake offline while onlining a section via online_page_callback) would under some condicions result in a kernel panic when dumping them. Link: http://lkml.kernel.org/r/20181119101616.8901-4-david@redhat.comSigned-off-by:
Michael S. Tsirkin <mst@redhat.com> Acked-by:
Dave Young <dyoung@redhat.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Baoquan He <bhe@redhat.com> Cc: Omar Sandoval <osandov@fb.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Lianbo Jiang <lijiang@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Christian Hansen <chansen3@cisco.com> Cc: David Rientjes <rientjes@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Juergen Gross <jgross@suse.com> Cc: Julien Freche <jfreche@vmware.com> Cc: Kairui Song <kasong@redhat.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Len Brown <len.brown@intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Nadav Amit <namit@vmware.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Pankaj gupta <pagupta@redhat.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Xavier Deguillard <xdeguillard@vmware.com> Signed-off-by:
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David Hildenbrand authored
PG_balloon was introduced to implement page migration/compaction for pages inflated in virtio-balloon. Nowadays, it is only a marker that a page is part of virtio-balloon and therefore logically offline. We also want to make use of this flag in other balloon drivers - for inflated pages or when onlining a section but keeping some pages offline (e.g. used right now by XEN and Hyper-V via set_online_page_callback()). We are going to expose this flag to dump tools like makedumpfile. But instead of exposing PG_balloon, let's generalize the concept of marking pages as logically offline, so it can be reused for other purposes later on. Rename PG_balloon to PG_offline. This is an indicator that the page is logically offline, the content stale and that it should not be touched (e.g. a hypervisor would have to allocate backing storage in order for the guest to dump an unused page). We can then e.g. exclude such pages from dumps. We replace and reuse KPF_BALLOON (23), as this shouldn't really harm (and for now the semantics stay the same). In following patches, we will make use of this bit also in other balloon drivers. While at it, document PGTABLE. [akpm@linux-foundation.org: fix comment text, per David] Link: http://lkml.kernel.org/r/20181119101616.8901-3-david@redhat.comSigned-off-by:
Konstantin Khlebnikov <koct9i@gmail.com> Acked-by:
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