65c8d30e67
Patch series "arm64: support batched/deferred tlb shootdown during page reclamation/migration", v11. Though ARM64 has the hardware to do tlb shootdown, the hardware broadcasting is not free. A simplest micro benchmark shows even on snapdragon 888 with only 8 cores, the overhead for ptep_clear_flush is huge even for paging out one page mapped by only one process: 5.36% a.out [kernel.kallsyms] [k] ptep_clear_flush While pages are mapped by multiple processes or HW has more CPUs, the cost should become even higher due to the bad scalability of tlb shootdown. The same benchmark can result in 16.99% CPU consumption on ARM64 server with around 100 cores according to the test on patch 4/4. This patchset leverages the existing BATCHED_UNMAP_TLB_FLUSH by 1. only send tlbi instructions in the first stage - arch_tlbbatch_add_mm() 2. wait for the completion of tlbi by dsb while doing tlbbatch sync in arch_tlbbatch_flush() Testing on snapdragon shows the overhead of ptep_clear_flush is removed by the patchset. The micro benchmark becomes 5% faster even for one page mapped by single process on snapdragon 888. Since BATCHED_UNMAP_TLB_FLUSH is implemented only on x86, the patchset does some renaming/extension for the current implementation first (Patch 1-3), then add the support on arm64 (Patch 4). This patch (of 4): The entire scheme of deferred TLB flush in reclaim path rests on the fact that the cost to refill TLB entries is less than flushing out individual entries by sending IPI to remote CPUs. But architecture can have different ways to evaluate that. Hence apart from checking TTU_BATCH_FLUSH in the TTU flags, rest of the decision should be architecture specific. [yangyicong@hisilicon.com: rebase and fix incorrect return value type] Link: https://lkml.kernel.org/r/20230717131004.12662-1-yangyicong@huawei.com Link: https://lkml.kernel.org/r/20230717131004.12662-2-yangyicong@huawei.com Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> [https://lore.kernel.org/linuxppc-dev/20171101101735.2318-2-khandual@linux.vnet.ibm.com/] Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> Reviewed-by: Barry Song <baohua@kernel.org> Reviewed-by: Xin Hao <xhao@linux.alibaba.com> Tested-by: Punit Agrawal <punit.agrawal@bytedance.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Darren Hart <darren@os.amperecomputing.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: lipeifeng <lipeifeng@oppo.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Steven Miao <realmz6@gmail.com> Cc: Will Deacon <will@kernel.org> Cc: Zeng Tao <prime.zeng@hisilicon.com> Cc: Barry Song <v-songbaohua@oppo.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Nadav Amit <namit@vmware.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.