- 30 Apr, 2021 40 commits
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Lukas Bulwahn authored
Patch series "kernel-doc and MAINTAINERS clean-up". Roughly 900 warnings of about 21.000 kernel-doc warnings in the kernel tree warn with 'cannot understand function prototype:', i.e., the kernel-doc parser cannot parse the function's signature. The majority, about 600 cases of those, are just struct definitions following the kernel-doc description. Further, spot-check investigations suggest that the authors of the specific kernel-doc descriptions simply were not aware that the general format for a kernel-doc description for a structure requires to prefix the struct name with the keyword 'struct', as in 'struct struct_name - Brief description.'. Details on kernel-doc are at the Link below. Without the struct keyword, kernel-doc does not check if the kernel-doc description fits to the actual struct definition in the source code. Fortunately, in roughly a quarter of these cases, the kernel-doc description is actually complete wrt. its corresponding struct definition. So, the trivial change adding the struct keyword will allow us to keep the kernel-doc descriptions more consistent for future changes, by checking for new kernel-doc warnings. Also, some of the files in ./include/ are not assigned to a specific MAINTAINERS section and hence have no dedicated maintainer. So, if needed, the files in ./include/ are also assigned to the fitting MAINTAINERS section, as I need to identify whom to send the clean-up patch anyway. Here is the change from this kernel-doc janitorial work in the ./include/ directory for MEMORY MANAGEMENT. This patch (of 2): Commit a520110e ("mm: split out a new pagewalk.h header from mm.h") adds a new file in ./include/linux, but misses to update MAINTAINERS accordingly. Hence, ./scripts/get_maintainers.pl include/linux/pagewalk.h points only to lkml as general fallback for all files, whereas the original include/linux/mm.h clearly marks this file part of MEMORY MANAGEMENT. Assign include/linux/pagewalk.h to MEMORY MANAGEMENT. Link: https://lkml.kernel.org/r/20210322122542.15072-1-lukas.bulwahn@gmail.com Link: https://lkml.kernel.org/r/20210322122542.15072-2-lukas.bulwahn@gmail.comSigned-off-by:
Lukas Bulwahn <lukas.bulwahn@gmail.com> Cc: Joe Perches <joe@perches.com> Cc: Ralf Ramsauer <ralf.ramsauer@oth-regensburg.de> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Matthew Wilcox (Oracle) authored
kerneldoc in include/linux/mm.h and include/linux/mm_types.h wasn't being included in the html build. Link: https://lkml.kernel.org/r/20210322195022.2143603-4-willy@infradead.orgSigned-off-by:
Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by:
Mike Rapoport <rppt@linux.ibm.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by:
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Matthew Wilcox (Oracle) authored
The kernel-doc script complains about include/linux/mm.h:425: warning: wrong kernel-doc identifier on line: * Fault flag definitions. I don't know how to document a series of #defines, so turn these definitions into an enum and document that instead. Link: https://lkml.kernel.org/r/20210322195022.2143603-3-willy@infradead.orgSigned-off-by:
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Matthew Wilcox (Oracle) authored
make htmldocs reports: include/linux/mm.h:1341: warning: Excess function parameter 'Return' description in 'page_maybe_dma_pinned' Fix a few other formatting nits while I'm editing this description. Link: https://lkml.kernel.org/r/20210322195022.2143603-2-willy@infradead.orgSigned-off-by:
John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by:
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Matthew Wilcox (Oracle) authored
make htmldocs reports: include/linux/mm.h:496: warning: Function parameter or member 'flags' not described in 'fault_flag_allow_retry_first' Add a description. Link: https://lkml.kernel.org/r/20210322195022.2143603-1-willy@infradead.orgSigned-off-by:
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Uladzislau Rezki (Sony) authored
Link: https://lkml.kernel.org/r/20210402202237.20334-5-urezki@gmail.comSigned-off-by:
Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Hillf Danton <hdanton@sina.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by:
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Uladzislau Rezki (Sony) authored
Instead of keeping open-coded style, move the code related to preloading into a separate function. Therefore introduce the preload_this_cpu_lock() routine that prelaods a current CPU with one extra vmap_area object. There is no functional change as a result of this patch. Link: https://lkml.kernel.org/r/20210402202237.20334-4-urezki@gmail.comSigned-off-by:
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Uladzislau Rezki (Sony) authored
A 'single_cpu_test' parameter is odd and it does not exist anymore. Instead there was introduced a 'nr_threads' one. If it is not set it behaves as the former parameter. That is why update a "stress mode" according to this change specifying number of workers which are equal to number of CPUs. Also update an output of help message based on a new interface. Link: https://lkml.kernel.org/r/20210402202237.20334-3-urezki@gmail.comSigned-off-by:
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Uladzislau Rezki (Sony) authored
By using this parameter we can specify how many workers are created to perform vmalloc tests. By default it is one CPU. The maximum value is set to 1024. As a result of this change a 'single_cpu_test' one becomes obsolete, therefore it is no longer needed. [urezki@gmail.com: extend max value of nr_threads parameter] Link: https://lkml.kernel.org/r/20210406124536.19658-1-urezki@gmail.com Link: https://lkml.kernel.org/r/20210402202237.20334-2-urezki@gmail.comSigned-off-by:
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Uladzislau Rezki (Sony) authored
Remove two test cases related to kvfree_rcu() and SLAB. Those are considered as redundant now, because similar test functionality has recently been introduced in the "rcuscale" RCU test-suite. Link: https://lkml.kernel.org/r/20210402202237.20334-1-urezki@gmail.comSigned-off-by:
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Vijayanand Jitta authored
A potential use after free can occur in _vm_unmap_aliases where an already freed vmap_area could be accessed, Consider the following scenario: Process 1 Process 2 __vm_unmap_aliases __vm_unmap_aliases purge_fragmented_blocks_allcpus rcu_read_lock() rcu_read_lock() list_del_rcu(&vb->free_list) list_for_each_entry_rcu(vb .. ) __purge_vmap_area_lazy kmem_cache_free(va) va_start = vb->va->va_start Here Process 1 is in purge path and it does list_del_rcu on vmap_block and later frees the vmap_area, since Process 2 was holding the rcu lock at this time vmap_block will still be present in and Process 2 accesse it and thereby it tries to access vmap_area of that vmap_block which was already freed by Process 1 and this results in use after free. Fix this by adding a check for vb->dirty before accessing vmap_area structure since vb->dirty will be set to VMAP_BBMAP_BITS in purge path checking for this will prevent the use after free. Link: https://lkml.kernel.org/r/1616062105-23263-1-git-send-email-vjitta@codeaurora.orgSigned-off-by:
Vijayanand Jitta <vjitta@codeaurora.org> Reviewed-by:
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Nicholas Piggin authored
There are several reasons why a vmalloc can fail, virtual space exhausted, page array allocation failure, page allocation failure, and kernel page table allocation failure. Add distinct warning messages for the main causes of failure, with some added information like page order or allocation size where applicable. [urezki@gmail.com: print correct vmalloc allocation size] Link: https://lkml.kernel.org/r/20210329193214.GA28602@pc638.lan Link: https://lkml.kernel.org/r/20210322021806.892164-6-npiggin@gmail.comSigned-off-by:
Nicholas Piggin <npiggin@gmail.com> Signed-off-by:
Christoph Hellwig <hch@lst.de> Cc: Cédric Le Goater <clg@kaod.org> Signed-off-by:
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Nicholas Piggin authored
This is a shim around vunmap_range, get rid of it. Move the main API comment from the _noflush variant to the normal variant, and make _noflush internal to mm/. [npiggin@gmail.com: fix nommu builds and a comment bug per sfr] Link: https://lkml.kernel.org/r/1617292598.m6g0knx24s.astroid@bobo.none [akpm@linux-foundation.org: move vunmap_range_noflush() stub inside !CONFIG_MMU, not !CONFIG_NUMA] [npiggin@gmail.com: fix nommu builds] Link: https://lkml.kernel.org/r/1617292497.o1uhq5ipxp.astroid@bobo.none Link: https://lkml.kernel.org/r/20210322021806.892164-5-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
iounmap will remove ptes. Link: https://lkml.kernel.org/r/20210322021806.892164-4-npiggin@gmail.comSigned-off-by:
Cédric Le Goater <clg@kaod.org> Cc: Uladzislau Rezki <urezki@gmail.com> Signed-off-by:
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Nicholas Piggin authored
vunmap will remove ptes. Link: https://lkml.kernel.org/r/20210322021806.892164-3-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
Patch series "mm/vmalloc: cleanup after hugepage series", v2. Christoph pointed out some overdue cleanups required after the huge vmalloc series, and I had another failure error message improvement as well. This patch (of 5): This is a shim around vmap_pages_range, get rid of it. Move the main API comment from the _noflush variant to the normal variant, and make _noflush internal to mm/. Link: https://lkml.kernel.org/r/20210322021806.892164-1-npiggin@gmail.com Link: https://lkml.kernel.org/r/20210322021806.892164-2-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
Support huge page vmalloc mappings. Config option HAVE_ARCH_HUGE_VMALLOC enables support on architectures that define HAVE_ARCH_HUGE_VMAP and supports PMD sized vmap mappings. vmalloc will attempt to allocate PMD-sized pages if allocating PMD size or larger, and fall back to small pages if that was unsuccessful. Architectures must ensure that any arch specific vmalloc allocations that require PAGE_SIZE mappings (e.g., module allocations vs strict module rwx) use the VM_NOHUGE flag to inhibit larger mappings. This can result in more internal fragmentation and memory overhead for a given allocation, an option nohugevmalloc is added to disable at boot. [colin.king@canonical.com: fix read of uninitialized pointer area] Link: https://lkml.kernel.org/r/20210318155955.18220-1-colin.king@canonical.com Link: https://lkml.kernel.org/r/20210317062402.533919-14-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
As a side-effect, the order of flush_cache_vmap() and arch_sync_kernel_mappings() calls are switched, but that now matches the other callers in this file. Link: https://lkml.kernel.org/r/20210317062402.533919-13-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
This is a generic kernel virtual memory mapper, not specific to ioremap. Code is unchanged other than making vmap_range non-static. Link: https://lkml.kernel.org/r/20210317062402.533919-12-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
If an architecture doesn't support a particular page table level as a huge vmap page size then allow it to skip defining the support query function. Link: https://lkml.kernel.org/r/20210317062402.533919-11-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
This allows unsupported levels to be constant folded away, and so p4d_free_pud_page can be removed because it's no longer linked to. Link: https://lkml.kernel.org/r/20210317062402.533919-10-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
This allows unsupported levels to be constant folded away, and so p4d_free_pud_page can be removed because it's no longer linked to. Link: https://lkml.kernel.org/r/20210317062402.533919-9-npiggin@gmail.comSigned-off-by:
Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Christoph Hellwig <hch@lst.de> Cc: Ding Tianhong <dingtianhong@huawei.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by:
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Nicholas Piggin authored
This allows unsupported levels to be constant folded away, and so p4d_free_pud_page can be removed because it's no longer linked to. Link: https://lkml.kernel.org/r/20210317062402.533919-8-npiggin@gmail.comSigned-off-by:
Michael Ellerman <mpe@ellerman.id.au> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Ding Tianhong <dingtianhong@huawei.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Will Deacon <will@kernel.org> Signed-off-by:
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Nicholas Piggin authored
This changes the awkward approach where architectures provide init functions to determine which levels they can provide large mappings for, to one where the arch is queried for each call. This removes code and indirection, and allows constant-folding of dead code for unsupported levels. This also adds a prot argument to the arch query. This is unused currently but could help with some architectures (e.g., some powerpc processors can't map uncacheable memory with large pages). Link: https://lkml.kernel.org/r/20210317062402.533919-7-npiggin@gmail.comSigned-off-by:
Ding Tianhong <dingtianhong@huawei.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> [arm64] Cc: Will Deacon <will@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Russell King <linux@armlinux.org.uk> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by:
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Nicholas Piggin authored
This will be used as a generic kernel virtual mapping function, so re-name it in preparation. Link: https://lkml.kernel.org/r/20210317062402.533919-6-npiggin@gmail.comSigned-off-by:
Miaohe Lin <linmiaohe@huawei.com> Reviewed-by:
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Nicholas Piggin authored
The vmalloc mapper operates on a struct page * array rather than a linear physical address, re-name it to make this distinction clear. Link: https://lkml.kernel.org/r/20210317062402.533919-5-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
apply_to_pte_range might mistake a large pte for bad, or treat it as a page table, resulting in a crash or corruption. Add a test to warn and return error if large entries are found. Link: https://lkml.kernel.org/r/20210317062402.533919-4-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
vmalloc_to_page returns NULL for addresses mapped by larger pages[*]. Whether or not a vmap is huge depends on the architecture details, alignments, boot options, etc., which the caller can not be expected to know. Therefore HUGE_VMAP is a regression for vmalloc_to_page. This change teaches vmalloc_to_page about larger pages, and returns the struct page that corresponds to the offset within the large page. This makes the API agnostic to mapping implementation details. [*] As explained by commit 029c54b0 ("mm/vmalloc.c: huge-vmap: fail gracefully on unexpected huge vmap mappings") [npiggin@gmail.com: sparc32: add stub pud_page define for walking huge vmalloc page tables] Link: https://lkml.kernel.org/r/20210324232825.1157363-1-npiggin@gmail.com Link: https://lkml.kernel.org/r/20210317062402.533919-3-npiggin@gmail.comSigned-off-by:
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Nicholas Piggin authored
Patch series "huge vmalloc mappings", v13. The kernel virtual mapping layer grew support for mapping memory with > PAGE_SIZE ptes with commit 0ddab1d2 ("lib/ioremap.c: add huge I/O map capability interfaces"), and implemented support for using those huge page mappings with ioremap. According to the submission, the use-case is mapping very large non-volatile memory devices, which could be GB or TB: https://lore.kernel.org/lkml/1425404664-19675-1-git-send-email-toshi.kani@hp.com/ The benefit is said to be in the overhead of maintaining the mapping, perhaps both in memory overhead and setup / teardown time. Memory overhead for the mapping with a 4kB page and 8 byte page table is 2GB per TB of mapping, down to 4MB / TB with 2MB pages. The same huge page vmap infrastructure can be quite easily adapted and used for mapping vmalloc memory pages without more complexity for arch or core vmap code. However unlike ioremap, vmalloc page table overhead is not a real problem, so the advantage to justify this is performance. Several of the most structures in the kernel (e.g., vfs and network hash tables) are allocated with vmalloc on NUMA machines, in order to distribute access bandwidth over the machine. Mapping these with larger pages can improve TLB usage significantly, for example this reduces TLB misses by nearly 30x on a `git diff` workload on a 2-node POWER9 (59,800 -> 2,100) and reduces CPU cycles by 0.54%, due to vfs hashes being allocated with 2MB pages. [ Other numbers? - The difference is even larger in a guest due to more costly TLB misses. - Eric Dumazet was keen on the network hash performance possibilities. - Other archs? Ding was doing x86 testing. ] The kernel module allocator also uses vmalloc to map module images even on non-NUMA, which can result in high iTLB pressure on highly modular distro type of kernels. This series does not implement huge mappings for modules yet, but it's a step along the way. Rick Edgecombe was looking at that IIRC. The per-cpu allocator similarly might be able to take advantage of this. Also on the todo list. The disadvantages of this I can see are: * Memory fragmentation can waste some physical memory because it will attempt to allocate larger pages to fit the required size, rounding up (once the requested size is >= 2MB). - I don't see it being a big problem in practice unless some user crops up that allocates thousands of 2.5MB ranges. We can tewak heuristics a bit there if needed to reduce peak waste. * Less granular mappings can make the NUMA distribution less balanced. - Similar to the above. - Could also allocate all major system hashes with one allocation up-front and spread them all across the one block, which should help overall NUMA distribution and reduce fragmentation waste. * Callers might expect something about the underlying allocated pages. - Tried to keep the apperance of base PAGE_SIZE pages throughout the APIs and exposed data structures. - Added a VM_NO_HUGE_VMAP flag to hammer troublesome cases with. - Finally, added a nohugevmalloc boot option to turn it off (independent of nohugeiomap). This patch (of 14): ARM uses its own PMD folding scheme which is missing pud_page which should just pass through to pmd_page. Move this from the 3-level page table to common header. Link: https://lkml.kernel.org/r/20210317062402.533919-2-npiggin@gmail.comSigned-off-by:
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Serapheim Dimitropoulos authored
vread() has been linearly searching vmap_area_list for looking up vmalloc areas to read from. These same areas are also tracked by a rb_tree (vmap_area_root) which offers logarithmic lookup. This patch modifies vread() to use the rb_tree structure instead of the list and the speedup for heavy /proc/kcore readers can be pretty significant. Below are the wall clock measurements of a Python application that leverages the drgn debugging library to read and interpret data read from /proc/kcore. Before the patch: ----- $ time sudo sdb -e 'dbuf | head 3000 | wc' (unsigned long)3000 real 0m22.446s user 0m2.321s sys 0m20.690s ----- With the patch: ----- $ time sudo sdb -e 'dbuf | head 3000 | wc' (unsigned long)3000 real 0m2.104s user 0m2.043s sys 0m0.921s ----- Link: https://lkml.kernel.org/r/20210209190253.108763-1-serapheim@delphix.comSigned-off-by:
Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by:
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Christoph Hellwig authored
remap_vmalloc_range_partial is only used to implement remap_vmalloc_range and by procfs. Unexport it. Link: https://lkml.kernel.org/r/20210301082235.932968-3-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Patch series "remap_vmalloc_range cleanups". This series removes an open coded instance of remap_vmalloc_range and removes the unused remap_vmalloc_range_partial export. This patch (of 2): Use remap_vmalloc_range instead of open coding it using remap_vmalloc_range_partial. Link: https://lkml.kernel.org/r/20210301082235.932968-1-hch@lst.de Link: https://lkml.kernel.org/r/20210301082235.932968-2-hch@lst.deSigned-off-by:
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Wang Wensheng authored
sparse_buffer_init() and sparse_buffer_fini() should appear in pair, or a WARN issue would be through the next time sparse_buffer_init() runs. Add the missing sparse_buffer_fini() in error branch. Link: https://lkml.kernel.org/r/20210325113155.118574-1-wangwensheng4@huawei.com Fixes: 85c77f79 ("mm/sparse: add new sparse_init_nid() and sparse_init()") Signed-off-by:
Wang Wensheng <wangwensheng4@huawei.com> Reviewed-by:
David Hildenbrand <david@redhat.com> Reviewed-by:
Oscar Salvador <osalvador@suse.de> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Signed-off-by:
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Zhiyuan Dai authored
strlcpy is marked as deprecated in Documentation/process/deprecated.rst, and there is no functional difference when the caller expects truncation (when not checking the return value). strscpy is relatively better as it also avoids scanning the whole source string. Link: https://lkml.kernel.org/r/1613962050-14188-1-git-send-email-daizhiyuan@phytium.com.cnSigned-off-by:
Zhiyuan Dai <daizhiyuan@phytium.com.cn> Signed-off-by:
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Brian Geffon authored
This test extends the current mremap tests to validate that the MREMAP_DONTUNMAP operation can be performed on shmem mappings. Link: https://lkml.kernel.org/r/20210323182520.2712101-3-bgeffon@google.comSigned-off-by:
Brian Geffon <bgeffon@google.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Lokesh Gidra <lokeshgidra@google.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Peter Xu <peterx@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: "Michael S . Tsirkin" <mst@redhat.com> Cc: Brian Geffon <bgeffon@google.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Sonny Rao <sonnyrao@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Dmitry Safonov <dima@arista.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Alejandro Colomar <alx.manpages@gmail.com> Signed-off-by:
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Brian Geffon authored
This reverts commit cd544fd1. As discussed in [1] this commit was a no-op because the mapping type was checked in vma_to_resize before move_vma is ever called. This meant that vm_ops->mremap() would never be called on such mappings. Furthermore, we've since expanded support of MREMAP_DONTUNMAP to non-anonymous mappings, and these special mappings are still protected by the existing check of !VM_DONTEXPAND and !VM_PFNMAP which will result in a -EINVAL. 1. https://lkml.org/lkml/2020/12/28/2340 Link: https://lkml.kernel.org/r/20210323182520.2712101-2-bgeffon@google.comSigned-off-by:
Hugh Dickins <hughd@google.com> Reviewed-by:
Dmitry Safonov <0x7f454c46@gmail.com> Cc: Alejandro Colomar <alx.manpages@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Lokesh Gidra <lokeshgidra@google.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: "Michael S . Tsirkin" <mst@redhat.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Peter Xu <peterx@redhat.com> Cc: Sonny Rao <sonnyrao@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by:
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Brian Geffon authored
Patch series "mm: Extend MREMAP_DONTUNMAP to non-anonymous mappings", v5. This patch (of 3): Currently MREMAP_DONTUNMAP only accepts private anonymous mappings. This restriction was placed initially for simplicity and not because there exists a technical reason to do so. This change will widen the support to include any mappings which are not VM_DONTEXPAND or VM_PFNMAP. The primary use case is to support MREMAP_DONTUNMAP on mappings which may have been created from a memfd. This change will result in mremap(MREMAP_DONTUNMAP) returning -EINVAL if VM_DONTEXPAND or VM_PFNMAP mappings are specified. Lokesh Gidra who works on the Android JVM, provided an explanation of how such a feature will improve Android JVM garbage collection: "Android is developing a new garbage collector (GC), based on userfaultfd. The garbage collector will use userfaultfd (uffd) on the java heap during compaction. On accessing any uncompacted page, the application threads will find it missing, at which point the thread will create the compacted page and then use UFFDIO_COPY ioctl to get it mapped and then resume execution. Before starting this compaction, in a stop-the-world pause the heap will be mremap(MREMAP_DONTUNMAP) so that the java heap is ready to receive UFFD_EVENT_PAGEFAULT events after resuming execution. To speedup mremap operations, pagetable movement was optimized by moving PUD entries instead of PTE entries [1]. It was necessary as mremap of even modest sized memory ranges also took several milliseconds, and stopping the application for that long isn't acceptable in response-time sensitive cases. With UFFDIO_CONTINUE feature [2], it will be even more efficient to implement this GC, particularly the 'non-moveable' portions of the heap. It will also help in reducing the need to copy (UFFDIO_COPY) the pages. However, for this to work, the java heap has to be on a 'shared' vma. Currently MREMAP_DONTUNMAP only supports private anonymous mappings, this patch will enable using UFFDIO_CONTINUE for the new userfaultfd-based heap compaction." [1] https://lore.kernel.org/linux-mm/20201215030730.NC3CU98e4%25akpm@linux-foundation.org/ [2] https://lore.kernel.org/linux-mm/20210302000133.272579-1-axelrasmussen@google.com/ Link: https://lkml.kernel.org/r/20210323182520.2712101-1-bgeffon@google.comSigned-off-by:
Lokesh Gidra <lokeshgidra@google.com> Reviewed-by:
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Huang Ying authored
With NUMA balancing, in hint page fault handler, the faulting page will be migrated to the accessing node if necessary. During the migration, TLB will be shot down on all CPUs that the process has run on recently. Because in the hint page fault handler, the PTE will be made accessible before the migration is tried. The overhead of TLB shooting down can be high, so it's better to be avoided if possible. In fact, if we delay mapping the page until migration, that can be avoided. This is what this patch doing. For the multiple threads applications, it's possible that a page is accessed by multiple threads almost at the same time. In the original implementation, because the first thread will install the accessible PTE before migrating the page, the other threads may access the page directly before the page is made inaccessible again during migration. While with the patch, the second thread will go through the page fault handler too. And because of the PageLRU() checking in the following code path, migrate_misplaced_page() numamigrate_isolate_page() isolate_lru_page() the migrate_misplaced_page() will return 0, and the PTE will be made accessible in the second thread. This will introduce a little more overhead. But we think the possibility for a page to be accessed by the multiple threads at the same time is low, and the overhead difference isn't too large. If this becomes a problem in some workloads, we need to consider how to reduce the overhead. To test the patch, we run a test case as follows on a 2-socket Intel server (1 NUMA node per socket) with 128GB DRAM (64GB per socket). 1. Run a memory eater on NUMA node 1 to use 40GB memory before running pmbench. 2. Run pmbench (normal accessing pattern) with 8 processes, and 8 threads per process, so there are 64 threads in total. The working-set size of each process is 8960MB, so the total working-set size is 8 * 8960MB = 70GB. The CPU of all pmbench processes is bound to node 1. The pmbench processes will access some DRAM on node 0. 3. After the pmbench processes run for 10 seconds, kill the memory eater. Now, some pages will be migrated from node 0 to node 1 via NUMA balancing. Test results show that, with the patch, the pmbench throughput (page accesses/s) increases 5.5%. The number of the TLB shootdowns interrupts reduces 98% (from ~4.7e7 to ~9.7e5) with about 9.2e6 pages (35.8GB) migrated. From the perf profile, it can be found that the CPU cycles spent by try_to_unmap() and its callees reduces from 6.02% to 0.47%. That is, the CPU cycles spent by TLB shooting down decreases greatly. Link: https://lkml.kernel.org/r/20210408132236.1175607-1-ying.huang@intel.comSigned-off-by:"Huang, Ying" <ying.huang@intel.com> Reviewed-by:
Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Peter Xu <peterx@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: "Matthew Wilcox" <willy@infradead.org> Cc: Will Deacon <will@kernel.org> Cc: Michel Lespinasse <walken@google.com> Cc: Arjun Roy <arjunroy@google.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Signed-off-by:
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Christoph Hellwig authored
remap_io_sg claims that the pgprot is pre-verified using an io_mapping, but actually does not get passed an io_mapping and just uses the pgprot in the VMA. Remove the apply_to_page_range abuse and just loop over remap_pfn_range for each segment. Note: this could use io_mapping_map_user by passing an iomap to remap_io_sg if the maintainers can verify that the pgprot in the iomap in the only caller is indeed the desired one here. Link: https://lkml.kernel.org/r/20210326055505.1424432-5-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Replace the home-grown remap_io_mapping that abuses apply_to_page_range with the proper io_mapping_map_user interface. Link: https://lkml.kernel.org/r/20210326055505.1424432-4-hch@lst.deSigned-off-by:
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