- 22 Feb, 2024 40 commits
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SeongJae Park authored
DAMOS operation actions are explained nearly twice on the DAMON usage document, once for the sysfs interface, and then again for the debugfs interface. Duplication is bad. Also it would better to keep this kind of concept level details in design document and keep the usage document small and focus on only the usage. Move the list to design document and update usage document to reference it. Link: https://lkml.kernel.org/r/20240217005842.87348-3-sj@kernel.orgSigned-off-by:
SeongJae Park <sj@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org>
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SeongJae Park authored
Patch series "Docs/mm/damon: misc readability improvements". Fix trivial mistakes and improve layout of information on different documents for DAMON. This patch (of 5): A couple of sentences on maintainer-profile.rst are having reference links for mm-unstable and mm-stable trees with wrong rst markup. Fix those. Link: https://lkml.kernel.org/r/20240217005842.87348-1-sj@kernel.org Link: https://lkml.kernel.org/r/20240217005842.87348-2-sj@kernel.orgSigned-off-by:
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Lokesh Gidra authored
All userfaultfd operations, except write-protect, opportunistically use per-vma locks to lock vmas. On failure, attempt again inside mmap_lock critical section. Write-protect operation requires mmap_lock as it iterates over multiple vmas. Link: https://lkml.kernel.org/r/20240215182756.3448972-5-lokeshgidra@google.comSigned-off-by:
Lokesh Gidra <lokeshgidra@google.com> Reviewed-by:
Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Brian Geffon <bgeffon@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Nicolas Geoffray <ngeoffray@google.com> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Tim Murray <timmurray@google.com> Signed-off-by:
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Lokesh Gidra authored
vma_assert_locked() is needed to replace mmap_assert_locked() once we start using per-vma locks in userfaultfd operations. In !CONFIG_PER_VMA_LOCK case when mm is locked, it implies that the given VMA is locked. Link: https://lkml.kernel.org/r/20240215182756.3448972-4-lokeshgidra@google.comSigned-off-by:
Suren Baghdasaryan <surenb@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Brian Geffon <bgeffon@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Nicolas Geoffray <ngeoffray@google.com> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Tim Murray <timmurray@google.com> Signed-off-by:
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Lokesh Gidra authored
Increments and loads to mmap_changing are always in mmap_lock critical section. This ensures that if userspace requests event notification for non-cooperative operations (e.g. mremap), userfaultfd operations don't occur concurrently. This can be achieved by using a separate read-write semaphore in userfaultfd_ctx such that increments are done in write-mode and loads in read-mode, thereby eliminating the dependency on mmap_lock for this purpose. This is a preparatory step before we replace mmap_lock usage with per-vma locks in fill/move ioctls. Link: https://lkml.kernel.org/r/20240215182756.3448972-3-lokeshgidra@google.comSigned-off-by:
Mike Rapoport (IBM) <rppt@kernel.org> Reviewed-by:
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Lokesh Gidra authored
Patch series "per-vma locks in userfaultfd", v7. Performing userfaultfd operations (like copy/move etc.) in critical section of mmap_lock (read-mode) causes significant contention on the lock when operations requiring the lock in write-mode are taking place concurrently. We can use per-vma locks instead to significantly reduce the contention issue. Android runtime's Garbage Collector uses userfaultfd for concurrent compaction. mmap-lock contention during compaction potentially causes jittery experience for the user. During one such reproducible scenario, we observed the following improvements with this patch-set: - Wall clock time of compaction phase came down from ~3s to <500ms - Uninterruptible sleep time (across all threads in the process) was ~10ms (none in mmap_lock) during compaction, instead of >20s This patch (of 4): Move the struct to userfaultfd_k.h to be accessible from mm/userfaultfd.c. There are no other changes in the struct. This is required to prepare for using per-vma locks in userfaultfd operations. Link: https://lkml.kernel.org/r/20240215182756.3448972-1-lokeshgidra@google.com Link: https://lkml.kernel.org/r/20240215182756.3448972-2-lokeshgidra@google.comSigned-off-by:
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Juntong Deng authored
In 5d4c6ac9 ("kasan: record and report more information") I thought that printk only displays a maximum of 99999 seconds, but actually printk can display a larger number of seconds. So increase the number of bits to shift when recording the extra timestamp (44 bits), without affecting the precision, shift it right by 9 bits, discarding all bits that do not affect the microsecond part (nanoseconds will not be shown). Currently the maximum time that can be displayed is 9007199.254740s, because 11111111111111111111111111111111111111111111 (44 bits) << 9 = 11111111111111111111111111111111111111111111000000000 = 9007199.254740 Link: https://lkml.kernel.org/r/AM6PR03MB58481629F2F28CE007412139994D2@AM6PR03MB5848.eurprd03.prod.outlook.com Fixes: 5d4c6ac9 ("kasan: record and report more information") Signed-off-by:
Juntong Deng <juntong.deng@outlook.com> Acked-by:
Andrey Konovalov <andreyknvl@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Signed-off-by:
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Matthew Wilcox (Oracle) authored
Removes two unnecessary conversions from folio to page. Should be no difference in behaviour. Link: https://lkml.kernel.org/r/20240215205307.674707-1-willy@infradead.orgSigned-off-by:
Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by:
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Mathieu Desnoyers authored
commit d92576f1 ("dax: does not work correctly with virtual aliasing caches") prevents DAX from building on architectures with virtually aliased dcache with: depends on !(ARM || MIPS || SPARC) This check is too broad (e.g. recent ARMv7 don't have virtually aliased dcaches), and also misses many other architectures with virtually aliased data cache. This is a regression introduced in the v4.0 Linux kernel where the dax mount option is removed for 32-bit ARMv7 boards which have no data cache aliasing, and therefore should work fine with FS_DAX. This was turned into the following check in alloc_dax() by a preparatory change: if (ops && (IS_ENABLED(CONFIG_ARM) || IS_ENABLED(CONFIG_MIPS) || IS_ENABLED(CONFIG_SPARC))) return NULL; Use cpu_dcache_is_aliasing() instead to figure out whether the environment has aliasing data caches. Link: https://lkml.kernel.org/r/20240215144633.96437-10-mathieu.desnoyers@efficios.com Fixes: d92576f1 ("dax: does not work correctly with virtual aliasing caches") Signed-off-by:
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reviewed-by:
Dan Williams <dan.j.williams@intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Russell King <linux@armlinux.org.uk> Cc: Alasdair Kergon <agk@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: kernel test robot <lkp@intel.com> Cc: Michael Sclafani <dm-devel@lists.linux.dev> Cc: Mike Snitzer <snitzer@kernel.org> Cc: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by:
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Mathieu Desnoyers authored
Introduce a generic way to query whether the data cache is virtually aliased on all architectures. Its purpose is to ensure that subsystems which are incompatible with virtually aliased data caches (e.g. FS_DAX) can reliably query this. For data cache aliasing, there are three scenarios dependending on the architecture. Here is a breakdown based on my understanding: A) The data cache is always aliasing: * arc * csky * m68k (note: shared memory mappings are incoherent ? SHMLBA is missing there.) * sh * parisc B) The data cache aliasing is statically known or depends on querying CPU state at runtime: * arm (cache_is_vivt() || cache_is_vipt_aliasing()) * mips (cpu_has_dc_aliases) * nios2 (NIOS2_DCACHE_SIZE > PAGE_SIZE) * sparc32 (vac_cache_size > PAGE_SIZE) * sparc64 (L1DCACHE_SIZE > PAGE_SIZE) * xtensa (DCACHE_WAY_SIZE > PAGE_SIZE) C) The data cache is never aliasing: * alpha * arm64 (aarch64) * hexagon * loongarch (but with incoherent write buffers, which are disabled since commit d23b7795 ("LoongArch: Change SHMLBA from SZ_64K to PAGE_SIZE")) * microblaze * openrisc * powerpc * riscv * s390 * um * x86 Require architectures in A) and B) to select ARCH_HAS_CPU_CACHE_ALIASING and implement "cpu_dcache_is_aliasing()". Architectures in C) don't select ARCH_HAS_CPU_CACHE_ALIASING, and thus cpu_dcache_is_aliasing() simply evaluates to "false". Note that this leaves "cpu_icache_is_aliasing()" to be implemented as future work. This would be useful to gate features like XIP on architectures which have aliasing CPU dcache-icache but not CPU dcache-dcache. Use "cpu_dcache" and "cpu_cache" rather than just "dcache" and "cache" to clarify that we really mean "CPU data cache" and "CPU cache" to eliminate any possible confusion with VFS "dentry cache" and "page cache". Link: https://lore.kernel.org/lkml/20030910210416.GA24258@mail.jlokier.co.uk/ Link: https://lkml.kernel.org/r/20240215144633.96437-9-mathieu.desnoyers@efficios.com Fixes: d92576f1 ("dax: does not work correctly with virtual aliasing caches") Signed-off-by: -
Mathieu Desnoyers authored
Replace the following fs/Kconfig:FS_DAX dependency: depends on !(ARM || MIPS || SPARC) By a runtime check within alloc_dax(). This runtime check returns ERR_PTR(-EOPNOTSUPP) if the @ops parameter is non-NULL (which means the kernel is using an aliased mapping) on an architecture which has data cache aliasing. Change the return value from NULL to PTR_ERR(-EOPNOTSUPP) for CONFIG_DAX=n for consistency. This is done in preparation for using cpu_dcache_is_aliasing() in a following change which will properly support architectures which detect data cache aliasing at runtime. Link: https://lkml.kernel.org/r/20240215144633.96437-8-mathieu.desnoyers@efficios.com Fixes: d92576f1 ("dax: does not work correctly with virtual aliasing caches") Signed-off-by:
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Mathieu Desnoyers authored
In preparation for checking whether the architecture has data cache aliasing within alloc_dax(), modify the error handling of virtio virtio_fs_setup_dax() to treat alloc_dax() -EOPNOTSUPP failure as non-fatal. Link: https://lkml.kernel.org/r/20240215144633.96437-7-mathieu.desnoyers@efficios.comCo-developed-by:
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Mathieu Desnoyers authored
In preparation for checking whether the architecture has data cache aliasing within alloc_dax(), modify the error handling of dcssblk dcssblk_add_store() to handle alloc_dax() -EOPNOTSUPP failures. Considering that s390 is not a data cache aliasing architecture, and considering that DCSSBLK selects DAX, a return value of -EOPNOTSUPP from alloc_dax() should make dcssblk_add_store() fail. Link: https://lkml.kernel.org/r/20240215144633.96437-6-mathieu.desnoyers@efficios.com Fixes: d92576f1 ("dax: does not work correctly with virtual aliasing caches") Signed-off-by:
Heiko Carstens <hca@linux.ibm.com> Cc: Alasdair Kergon <agk@redhat.com> Cc: Mike Snitzer <snitzer@kernel.org> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Russell King <linux@armlinux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: kernel test robot <lkp@intel.com> Cc: Michael Sclafani <dm-devel@lists.linux.dev> Signed-off-by:
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Mathieu Desnoyers authored
In preparation for checking whether the architecture has data cache aliasing within alloc_dax(), modify the error handling of dm alloc_dev() to treat alloc_dax() -EOPNOTSUPP failure as non-fatal. Link: https://lkml.kernel.org/r/20240215144633.96437-5-mathieu.desnoyers@efficios.com Fixes: d92576f1 ("dax: does not work correctly with virtual aliasing caches") Suggested-by:
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Mathieu Desnoyers authored
In preparation for checking whether the architecture has data cache aliasing within alloc_dax(), modify the error handling of nvdimm/pmem pmem_attach_disk() to treat alloc_dax() -EOPNOTSUPP failure as non-fatal. [ Based on commit "nvdimm/pmem: Fix leak on dax_add_host() failure". ] Link: https://lkml.kernel.org/r/20240215144633.96437-4-mathieu.desnoyers@efficios.com Fixes: d92576f1 ("dax: does not work correctly with virtual aliasing caches") Signed-off-by:
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Mathieu Desnoyers authored
Change the return value from NULL to PTR_ERR(-EOPNOTSUPP) for CONFIG_DAX=n to be consistent with the fact that CONFIG_DAX=y never returns NULL. This is done in preparation for using cpu_dcache_is_aliasing() in a following change which will properly support architectures which detect data cache aliasing at runtime. Link: https://lkml.kernel.org/r/20240215144633.96437-3-mathieu.desnoyers@efficios.com Fixes: 4e4ced93 ("dax: Move mandatory ->zero_page_range() check in alloc_dax()") Signed-off-by:
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Mathieu Desnoyers authored
Patch series "Introduce cpu_dcache_is_aliasing() to fix DAX regression", v6. This commit introduced in v4.0 prevents building FS_DAX on 32-bit ARM, even on ARMv7 which does not have virtually aliased data caches: commit d92576f1 ("dax: does not work correctly with virtual aliasing caches") Even though it used to work fine before. The root of the issue here is the fact that DAX was never designed to handle virtually aliasing data caches (VIVT and VIPT with aliasing data cache). It touches the pages through their linear mapping, which is not consistent with the userspace mappings with virtually aliasing data caches. This patch series introduces cpu_dcache_is_aliasing() with the new Kconfig option ARCH_HAS_CPU_CACHE_ALIASING and implements it for all architectures. The implementation of cpu_dcache_is_aliasing() is either evaluated to a constant at compile-time or a runtime check, which is what is needed on ARM. With this we can basically narrow down the list of architectures which are unsupported by DAX to those which are really affected. This patch (of 9): When building a kernel with CONFIG_DAX=n, all uses of set_dax_nocache() and set_dax_nomc() need to be either within regions of code or compile units which are explicitly not compiled, or they need to rely on compiler optimizations to eliminate calls to those undefined symbols. It appears that at least the openrisc and loongarch architectures don't end up eliminating those undefined symbols even if they are provably within code which is eliminated due to conditional branches depending on constants. Implement empty static inline functions for set_dax_nocache() and set_dax_nomc() in CONFIG_DAX=n to ensure those undefined references are removed. Link: https://lkml.kernel.org/r/20240215144633.96437-1-mathieu.desnoyers@efficios.com Link: https://lkml.kernel.org/r/20240215144633.96437-2-mathieu.desnoyers@efficios.comReported-by:
kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202402140037.wGfA1kqX-lkp@intel.com/Reported-by:
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Mathieu Desnoyers authored
Fix a leak on dax_add_host() error, where "goto out_cleanup_dax" is done before setting pmem->dax_dev, which therefore issues the two following calls on NULL pointers: out_cleanup_dax: kill_dax(pmem->dax_dev); put_dax(pmem->dax_dev); Link: https://lkml.kernel.org/r/20240208184913.484340-1-mathieu.desnoyers@efficios.com Link: https://lkml.kernel.org/r/20240208184913.484340-2-mathieu.desnoyers@efficios.comSigned-off-by:Fan Ni <fan.ni@samsung.com> Reviewed-by:
Dave Jiang <dave.jiang@intel.com> Cc: Alasdair Kergon <agk@redhat.com> Cc: Mike Snitzer <snitzer@kernel.org> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Russell King <linux@armlinux.org.uk> Cc: Dave Chinner <david@fromorbit.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by:
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Ryan Roberts authored
There are situations where a change to a single PTE could cause the contpte block in which it resides to become foldable (i.e. could be repainted with the contiguous bit). Such situations arise, for example, when user space temporarily changes protections, via mprotect, for individual pages, such can be the case for certain garbage collectors. We would like to detect when such a PTE change occurs. However this can be expensive due to the amount of checking required. Therefore only perform the checks when an indiviual PTE is modified via mprotect (ptep_modify_prot_commit() -> set_pte_at() -> set_ptes(nr=1)) and only when we are setting the final PTE in a contpte-aligned block. Link: https://lkml.kernel.org/r/20240215103205.2607016-19-ryan.roberts@arm.comSigned-off-by:
Ryan Roberts <ryan.roberts@arm.com> Acked-by:
Mark Rutland <mark.rutland@arm.com> Acked-by:
Catalin Marinas <catalin.marinas@arm.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Barry Song <21cnbao@gmail.com> Cc: Borislav Petkov (AMD) <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Morse <james.morse@arm.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by:
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Ryan Roberts authored
As set_ptes() and wrprotect_ptes() become a bit more complex, the compiler may choose not to inline them. But this is critical for fork() performance. So mark the functions, along with contpte_try_unfold() which is called by them, as __always_inline. This is worth ~1% on the fork() microbenchmark with order-0 folios (the common case). Link: https://lkml.kernel.org/r/20240215103205.2607016-18-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
When core code iterates over a range of ptes and calls ptep_get() for each of them, if the range happens to cover contpte mappings, the number of pte reads becomes amplified by a factor of the number of PTEs in a contpte block. This is because for each call to ptep_get(), the implementation must read all of the ptes in the contpte block to which it belongs to gather the access and dirty bits. This causes a hotspot for fork(), as well as operations that unmap memory such as munmap(), exit and madvise(MADV_DONTNEED). Fortunately we can fix this by implementing pte_batch_hint() which allows their iterators to skip getting the contpte tail ptes when gathering the batch of ptes to operate on. This results in the number of PTE reads returning to 1 per pte. Link: https://lkml.kernel.org/r/20240215103205.2607016-17-ryan.roberts@arm.comSigned-off-by:
David Hildenbrand <david@redhat.com> Tested-by:
John Hubbard <jhubbard@nvidia.com> Acked-by:
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Ryan Roberts authored
Some architectures (e.g. arm64) can tell from looking at a pte, if some follow-on ptes also map contiguous physical memory with the same pgprot. (for arm64, these are contpte mappings). Take advantage of this knowledge to optimize folio_pte_batch() so that it can skip these ptes when scanning to create a batch. By default, if an arch does not opt-in, folio_pte_batch() returns a compile-time 1, so the changes are optimized out and the behaviour is as before. arm64 will opt-in to providing this hint in the next patch, which will greatly reduce the cost of ptep_get() when scanning a range of contptes. Link: https://lkml.kernel.org/r/20240215103205.2607016-16-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Optimize the contpte implementation to fix some of the exit/munmap/dontneed performance regression introduced by the initial contpte commit. Subsequent patches will solve it entirely. During exit(), munmap() or madvise(MADV_DONTNEED), mappings must be cleared. Previously this was done 1 PTE at a time. But the core-mm supports batched clear via the new [get_and_]clear_full_ptes() APIs. So let's implement those APIs and for fully covered contpte mappings, we no longer need to unfold the contpte. This significantly reduces unfolding operations, reducing the number of tlbis that must be issued. Link: https://lkml.kernel.org/r/20240215103205.2607016-15-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Optimize the contpte implementation to fix some of the fork performance regression introduced by the initial contpte commit. Subsequent patches will solve it entirely. During fork(), any private memory in the parent must be write-protected. Previously this was done 1 PTE at a time. But the core-mm supports batched wrprotect via the new wrprotect_ptes() API. So let's implement that API and for fully covered contpte mappings, we no longer need to unfold the contpte. This has 2 benefits: - reduced unfolding, reduces the number of tlbis that must be issued. - The memory remains contpte-mapped ("folded") in the parent, so it continues to benefit from the more efficient use of the TLB after the fork. The optimization to wrprotect a whole contpte block without unfolding is possible thanks to the tightening of the Arm ARM in respect to the definition and behaviour when 'Misprogramming the Contiguous bit'. See section D21194 at https://developer.arm.com/documentation/102105/ja-07/ Link: https://lkml.kernel.org/r/20240215103205.2607016-14-ryan.roberts@arm.comSigned-off-by: -
Ryan Roberts authored
With the ptep API sufficiently refactored, we can now introduce a new "contpte" API layer, which transparently manages the PTE_CONT bit for user mappings. In this initial implementation, only suitable batches of PTEs, set via set_ptes(), are mapped with the PTE_CONT bit. Any subsequent modification of individual PTEs will cause an "unfold" operation to repaint the contpte block as individual PTEs before performing the requested operation. While, a modification of a single PTE could cause the block of PTEs to which it belongs to become eligible for "folding" into a contpte entry, "folding" is not performed in this initial implementation due to the costs of checking the requirements are met. Due to this, contpte mappings will degrade back to normal pte mappings over time if/when protections are changed. This will be solved in a future patch. Since a contpte block only has a single access and dirty bit, the semantic here changes slightly; when getting a pte (e.g. ptep_get()) that is part of a contpte mapping, the access and dirty information are pulled from the block (so all ptes in the block return the same access/dirty info). When changing the access/dirty info on a pte (e.g. ptep_set_access_flags()) that is part of a contpte mapping, this change will affect the whole contpte block. This is works fine in practice since we guarantee that only a single folio is mapped by a contpte block, and the core-mm tracks access/dirty information per folio. In order for the public functions, which used to be pure inline, to continue to be callable by modules, export all the contpte_* symbols that are now called by those public inline functions. The feature is enabled/disabled with the ARM64_CONTPTE Kconfig parameter at build time. It defaults to enabled as long as its dependency, TRANSPARENT_HUGEPAGE is also enabled. The core-mm depends upon TRANSPARENT_HUGEPAGE to be able to allocate large folios, so if its not enabled, then there is no chance of meeting the physical contiguity requirement for contpte mappings. Link: https://lkml.kernel.org/r/20240215103205.2607016-13-ryan.roberts@arm.comSigned-off-by:
Ard Biesheuvel <ardb@kernel.org> Tested-by:
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Ryan Roberts authored
Split __flush_tlb_range() into __flush_tlb_range_nosync() + __flush_tlb_range(), in the same way as the existing flush_tlb_page() arrangement. This allows calling __flush_tlb_range_nosync() to elide the trailing DSB. Forthcoming "contpte" code will take advantage of this when clearing the young bit from a contiguous range of ptes. Ordering between dsb and mmu_notifier_arch_invalidate_secondary_tlbs() has changed, but now aligns with the ordering of __flush_tlb_page(). It has been discussed that __flush_tlb_page() may be wrong though. Regardless, both will be resolved separately if needed. Link: https://lkml.kernel.org/r/20240215103205.2607016-12-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Create a new layer for the in-table PTE manipulation APIs. For now, The existing API is prefixed with double underscore to become the arch-private API and the public API is just a simple wrapper that calls the private API. The public API implementation will subsequently be used to transparently manipulate the contiguous bit where appropriate. But since there are already some contig-aware users (e.g. hugetlb, kernel mapper), we must first ensure those users use the private API directly so that the future contig-bit manipulations in the public API do not interfere with those existing uses. The following APIs are treated this way: - ptep_get - set_pte - set_ptes - pte_clear - ptep_get_and_clear - ptep_test_and_clear_young - ptep_clear_flush_young - ptep_set_wrprotect - ptep_set_access_flags Link: https://lkml.kernel.org/r/20240215103205.2607016-11-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
ptep_clear() is a generic wrapper around the arch-implemented ptep_get_and_clear(). We are about to convert ptep_get_and_clear() into a public version and private version (__ptep_get_and_clear()) to support the transparent contpte work. We won't have a private version of ptep_clear() so let's convert it to directly call ptep_get_and_clear(). Link: https://lkml.kernel.org/r/20240215103205.2607016-10-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Since set_ptes() was introduced, set_pte_at() has been implemented as a generic macro around set_ptes(..., 1). So this change should continue to generate the same code. However, making this change prepares us for the transparent contpte support. It means we can reroute set_ptes() to __set_ptes(). Since set_pte_at() is a generic macro, there will be no equivalent __set_pte_at() to reroute to. Note that a couple of calls to set_pte_at() remain in the arch code. This is intentional, since those call sites are acting on behalf of core-mm and should continue to call into the public set_ptes() rather than the arch-private __set_ptes(). Link: https://lkml.kernel.org/r/20240215103205.2607016-9-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
There are a number of places in the arch code that read a pte by using the READ_ONCE() macro. Refactor these call sites to instead use the ptep_get() helper, which itself is a READ_ONCE(). Generated code should be the same. This will benefit us when we shortly introduce the transparent contpte support. In this case, ptep_get() will become more complex so we now have all the code abstracted through it. Link: https://lkml.kernel.org/r/20240215103205.2607016-8-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Now that the all architecture overrides of pte_next_pfn() have been replaced with pte_advance_pfn(), we can simplify the definition of the generic pte_next_pfn() macro so that it is unconditionally defined. Link: https://lkml.kernel.org/r/20240215103205.2607016-7-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Core-mm needs to be able to advance the pfn by an arbitrary amount, so override the new pte_advance_pfn() API to do so. Link: https://lkml.kernel.org/r/20240215103205.2607016-6-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Core-mm needs to be able to advance the pfn by an arbitrary amount, so override the new pte_advance_pfn() API to do so. Link: https://lkml.kernel.org/r/20240215103205.2607016-5-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
The goal is to be able to advance a PTE by an arbitrary number of PFNs. So introduce a new API that takes a nr param. Define the default implementation here and allow for architectures to override. pte_next_pfn() becomes a wrapper around pte_advance_pfn(). Follow up commits will convert each overriding architecture's pte_next_pfn() to pte_advance_pfn(). Link: https://lkml.kernel.org/r/20240215103205.2607016-4-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Refactor __split_huge_pmd_locked() so that a present PMD can be collapsed to PTEs in a single batch using set_ptes(). This should improve performance a little bit, but the real motivation is to remove the need for the arm64 backend to have to fold the contpte entries. Instead, since the ptes are set as a batch, the contpte blocks can be initially set up pre-folded (once the arm64 contpte support is added in the next few patches). This leads to noticeable performance improvement during split. Link: https://lkml.kernel.org/r/20240215103205.2607016-3-ryan.roberts@arm.comSigned-off-by:
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Ryan Roberts authored
Patch series "Transparent Contiguous PTEs for User Mappings", v6. This is a series to opportunistically and transparently use contpte mappings (set the contiguous bit in ptes) for user memory when those mappings meet the requirements. The change benefits arm64, but there is some (very) minor refactoring for x86 to enable its integration with core-mm. It is part of a wider effort to improve performance by allocating and mapping variable-sized blocks of memory (folios). One aim is for the 4K kernel to approach the performance of the 16K kernel, but without breaking compatibility and without the associated increase in memory. Another aim is to benefit the 16K and 64K kernels by enabling 2M THP, since this is the contpte size for those kernels. We have good performance data that demonstrates both aims are being met (see below). Of course this is only one half of the change. We require the mapped physical memory to be the correct size and alignment for this to actually be useful (i.e. 64K for 4K pages, or 2M for 16K/64K pages). Fortunately folios are solving this problem for us. Filesystems that support it (XFS, AFS, EROFS, tmpfs, ...) will allocate large folios up to the PMD size today, and more filesystems are coming. And for anonymous memory, "multi-size THP" is now upstream. Patch Layout ============ In this version, I've split the patches to better show each optimization: - 1-2: mm prep: misc code and docs cleanups - 3-6: mm,arm64,x86 prep: Add pte_advance_pfn() and make pte_next_pfn() a generic wrapper around it - 7-11: arm64 prep: Refactor ptep helpers into new layer - 12: functional contpte implementation - 23-18: various optimizations on top of the contpte implementation Testing ======= I've tested this series on both Ampere Altra (bare metal) and Apple M2 (VM): - mm selftests (inc new tests written for multi-size THP); no regressions - Speedometer Java script benchmark in Chromium web browser; no issues - Kernel compilation; no issues - Various tests under high memory pressure with swap enabled; no issues Performance =========== High Level Use Cases ~~~~~~~~~~~~~~~~~~~~ First some high level use cases (kernel compilation and speedometer JavaScript benchmarks). These are running on Ampere Altra (I've seen similar improvements on Android/Pixel 6). baseline: mm-unstable (mTHP switched off) mTHP: + enable 16K, 32K, 64K mTHP sizes "always" mTHP + contpte: + this series mTHP + contpte + exefolio: + patch at [6], which series supports Kernel Compilation with -j8 (negative is faster): | kernel | real-time | kern-time | user-time | |---------------------------|-----------|-----------|-----------| | baseline | 0.0% | 0.0% | 0.0% | | mTHP | -5.0% | -39.1% | -0.7% | | mTHP + contpte | -6.0% | -41.4% | -1.5% | | mTHP + contpte + exefolio | -7.8% | -43.1% | -3.4% | Kernel Compilation with -j80 (negative is faster): | kernel | real-time | kern-time | user-time | |---------------------------|-----------|-----------|-----------| | baseline | 0.0% | 0.0% | 0.0% | | mTHP | -5.0% | -36.6% | -0.6% | | mTHP + contpte | -6.1% | -38.2% | -1.6% | | mTHP + contpte + exefolio | -7.4% | -39.2% | -3.2% | Speedometer (positive is faster): | kernel | runs_per_min | |:--------------------------|--------------| | baseline | 0.0% | | mTHP | 1.5% | | mTHP + contpte | 3.2% | | mTHP + contpte + exefolio | 4.5% | Micro Benchmarks ~~~~~~~~~~~~~~~~ The following microbenchmarks are intended to demonstrate the performance of fork() and munmap() do not regress. I'm showing results for order-0 (4K) mappings, and for order-9 (2M) PTE-mapped THP. Thanks to David for sharing his benchmarks. baseline: mm-unstable + batch zap [7] series contpte-basic: + patches 0-19; functional contpte implementation contpte-batch: + patches 20-23; implement new batched APIs contpte-inline: + patch 24; __always_inline to help compiler contpte-fold: + patch 25; fold contpte mapping when sensible Primary platform is Ampere Altra bare metal. I'm also showing results for M2 VM (on top of MacOS) for reference, although experience suggests this might not be the most reliable for performance numbers of this sort: | FORK | order-0 | order-9 | | Ampere Altra |------------------------|------------------------| | (pte-map) | mean | stdev | mean | stdev | |----------------|------------|-----------|------------|-----------| | baseline | 0.0% | 2.7% | 0.0% | 0.2% | | contpte-basic | 6.3% | 1.4% | 1948.7% | 0.2% | | contpte-batch | 7.6% | 2.0% | -1.9% | 0.4% | | contpte-inline | 3.6% | 1.5% | -1.0% | 0.2% | | contpte-fold | 4.6% | 2.1% | -1.8% | 0.2% | | MUNMAP | order-0 | order-9 | | Ampere Altra |------------------------|------------------------| | (pte-map) | mean | stdev | mean | stdev | |----------------|------------|-----------|------------|-----------| | baseline | 0.0% | 0.5% | 0.0% | 0.3% | | contpte-basic | 1.8% | 0.3% | 1104.8% | 0.1% | | contpte-batch | -0.3% | 0.4% | 2.7% | 0.1% | | contpte-inline | -0.1% | 0.6% | 0.9% | 0.1% | | contpte-fold | 0.1% | 0.6% | 0.8% | 0.1% | | FORK | order-0 | order-9 | | Apple M2 VM |------------------------|------------------------| | (pte-map) | mean | stdev | mean | stdev | |----------------|------------|-----------|------------|-----------| | baseline | 0.0% | 1.4% | 0.0% | 0.8% | | contpte-basic | 6.8% | 1.2% | 469.4% | 1.4% | | contpte-batch | -7.7% | 2.0% | -8.9% | 0.7% | | contpte-inline | -6.0% | 2.1% | -6.0% | 2.0% | | contpte-fold | 5.9% | 1.4% | -6.4% | 1.4% | | MUNMAP | order-0 | order-9 | | Apple M2 VM |------------------------|------------------------| | (pte-map) | mean | stdev | mean | stdev | |----------------|------------|-----------|------------|-----------| | baseline | 0.0% | 0.6% | 0.0% | 0.4% | | contpte-basic | 1.6% | 0.6% | 233.6% | 0.7% | | contpte-batch | 1.9% | 0.3% | -3.9% | 0.4% | | contpte-inline | 2.2% | 0.8% | -1.6% | 0.9% | | contpte-fold | 1.5% | 0.7% | -1.7% | 0.7% | Misc ~~~~ John Hubbard at Nvidia has indicated dramatic 10x performance improvements for some workloads at [8], when using 64K base page kernel. [1] https://lore.kernel.org/linux-arm-kernel/20230622144210.2623299-1-ryan.roberts@arm.com/ [2] https://lore.kernel.org/linux-arm-kernel/20231115163018.1303287-1-ryan.roberts@arm.com/ [3] https://lore.kernel.org/linux-arm-kernel/20231204105440.61448-1-ryan.roberts@arm.com/ [4] https://lore.kernel.org/lkml/20231218105100.172635-1-ryan.roberts@arm.com/ [5] https://lore.kernel.org/linux-mm/633af0a7-0823-424f-b6ef-374d99483f05@arm.com/ [6] https://lore.kernel.org/lkml/08c16f7d-f3b3-4f22-9acc-da943f647dc3@arm.com/ [7] https://lore.kernel.org/linux-mm/20240214204435.167852-1-david@redhat.com/ [8] https://lore.kernel.org/linux-mm/c507308d-bdd4-5f9e-d4ff-e96e4520be85@nvidia.com/ [9] https://gitlab.arm.com/linux-arm/linux-rr/-/tree/features/granule_perf/contpte-lkml_v6 This patch (of 18): set_ptes() spec implies that it can only be used to set a present pte because it interprets the PFN field to increment it. However, set_pte_at() has been implemented on top of set_ptes() since set_ptes() was introduced, and set_pte_at() allows setting a pte to a not-present state. So clarify the spec to state that when nr==1, new state of pte may be present or not present. When nr>1, new state of all ptes must be present. While we are at it, tighten the spec to set requirements around the initial state of ptes; when nr==1 it may be either present or not-present. But when nr>1 all ptes must initially be not-present. All set_ptes() callsites already conform to this requirement. Stating it explicitly is useful because it allows for a simplification to the upcoming arm64 contpte implementation. Link: https://lkml.kernel.org/r/20240215103205.2607016-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20240215103205.2607016-2-ryan.roberts@arm.comSigned-off-by: -
David Hildenbrand authored
Similar to how we optimized fork(), let's implement PTE batching when consecutive (present) PTEs map consecutive pages of the same large folio. Most infrastructure we need for batching (mmu gather, rmap) is already there. We only have to add get_and_clear_full_ptes() and clear_full_ptes(). Similarly, extend zap_install_uffd_wp_if_needed() to process a PTE range. We won't bother sanity-checking the mapcount of all subpages, but only check the mapcount of the first subpage we process. If there is a real problem hiding somewhere, we can trigger it simply by using small folios, or when we zap single pages of a large folio. Ideally, we had that check in rmap code (including for delayed rmap), but then we cannot print the PTE. Let's keep it simple for now. If we ever have a cheap folio_mapcount(), we might just want to check for underflows there. To keep small folios as fast as possible force inlining of a specialized variant using __always_inline with nr=1. Link: https://lkml.kernel.org/r/20240214204435.167852-11-david@redhat.comSigned-off-by:
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David Hildenbrand authored
In tlb_batch_pages_flush(), we can end up freeing up to 512 pages or now up to 256 folio fragments that span more than one page, before we conditionally reschedule. It's a pain that we have to handle cond_resched() in tlb_batch_pages_flush() manually and cannot simply handle it in release_pages() -- release_pages() can be called from atomic context. Well, in a perfect world we wouldn't have to make our code more complicated at all. With page poisoning and init_on_free, we might now run into soft lockups when we free a lot of rather large folio fragments, because page freeing time then depends on the actual memory size we are freeing instead of on the number of folios that are involved. In the absolute (unlikely) worst case, on arm64 with 64k we will be able to free up to 256 folio fragments that each span 512 MiB: zeroing out 128 GiB does sound like it might take a while. But instead of ignoring this unlikely case, let's just handle it. So, let's teach tlb_batch_pages_flush() that there are some configurations where page freeing is horribly slow, and let's reschedule more frequently -- similarly like we did for now before we had large folio fragments in there. Avoid yet another loop over all encoded pages in the common case by handling that separately. Note that with page poisoning/zeroing, we might now end up freeing only a single folio fragment at a time that might exceed the old 512 pages limit: but if we cannot even free a single MAX_ORDER page on a system without running into soft lockups, something else is already completely bogus. Freeing a PMD-mapped THP would similarly cause trouble. In theory, we might even free 511 order-0 pages + a single MAX_ORDER page, effectively having to zero out 8703 pages on arm64 with 64k, translating to ~544 MiB of memory: however, if 512 MiB doesn't result in soft lockups, 544 MiB is unlikely to result in soft lockups, so we won't care about that for the time being. In the future, we might want to detect if handling cond_resched() is required at all, and just not do any of that with full preemption enabled. Link: https://lkml.kernel.org/r/20240214204435.167852-10-david@redhat.comSigned-off-by:
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David Hildenbrand authored
Add __tlb_remove_folio_pages(), which will remove multiple consecutive pages that belong to the same large folio, instead of only a single page. We'll be using this function when optimizing unmapping/zapping of large folios that are mapped by PTEs. We're using the remaining spare bit in an encoded_page to indicate that the next enoced page in an array contains actually shifted "nr_pages". Teach swap/freeing code about putting multiple folio references, and delayed rmap handling to remove page ranges of a folio. This extension allows for still gathering almost as many small folios as we used to (-1, because we have to prepare for a possibly bigger next entry), but still allows for gathering consecutive pages that belong to the same large folio. Note that we don't pass the folio pointer, because it is not required for now. Further, we don't support page_size != PAGE_SIZE, it won't be required for simple PTE batching. We have to provide a separate s390 implementation, but it's fairly straight forward. Another, more invasive and likely more expensive, approach would be to use folio+range or a PFN range instead of page+nr_pages. But, we should do that consistently for the whole mmu_gather. For now, let's keep it simple and add "nr_pages" only. Note that it is now possible to gather significantly more pages: In the past, we were able to gather ~10000 pages, now we can also gather ~5000 folio fragments that span multiple pages. A folio fragment on x86-64 can span up to 512 pages (2 MiB THP) and on arm64 with 64k in theory 8192 pages (512 MiB THP). Gathering more memory is not considered something we should worry about, especially because these are already corner cases. While we can gather more total memory, we won't free more folio fragments. As long as page freeing time primarily only depends on the number of involved folios, there is no effective change for !preempt configurations. However, we'll adjust tlb_batch_pages_flush() separately to handle corner cases where page freeing time grows proportionally with the actual memory size. Link: https://lkml.kernel.org/r/20240214204435.167852-9-david@redhat.comSigned-off-by:
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David Hildenbrand authored
Let's add a helper that lets us batch-process multiple consecutive PTEs. Note that the loop will get optimized out on all architectures except on powerpc. We have to add an early define of __tlb_remove_tlb_entry() on ppc to make the compiler happy (and avoid making tlb_remove_tlb_entries() a macro). [arnd@kernel.org: change __tlb_remove_tlb_entry() to an inline function] Link: https://lkml.kernel.org/r/20240221154549.2026073-1-arnd@kernel.org Link: https://lkml.kernel.org/r/20240214204435.167852-8-david@redhat.comSigned-off-by:
Arnd Bergmann <arnd@arndb.de> Reviewed-by:
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