Hi mm and arm64 maintainers, a gentle ping for this.. Thanks. On 2022/8/22 16:21, Yicong Yang wrote: > From: Yicong Yang <yangyicong@xxxxxxxxxxxxx> > > 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 Yicong's 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() > My 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. > > -v3: > 1. Declare arch's tlbbatch defer support by arch_tlbbatch_should_defer() instead > of ARCH_HAS_MM_CPUMASK, per Barry and Kefeng > 2. Add Tested-by from Xin Hao > Link: https://lore.kernel.org/linux-mm/20220711034615.482895-1-21cnbao@xxxxxxxxx/ > > -v2: > 1. Collected Yicong's test result on kunpeng920 ARM64 server; > 2. Removed the redundant vma parameter in arch_tlbbatch_add_mm() > according to the comments of Peter Zijlstra and Dave Hansen > 3. Added ARCH_HAS_MM_CPUMASK rather than checking if mm_cpumask > is empty according to the comments of Nadav Amit > > Thanks, Peter, Dave and Nadav for your testing or reviewing > , and comments. > > -v1: > https://lore.kernel.org/lkml/20220707125242.425242-1-21cnbao@xxxxxxxxx/ > > Anshuman Khandual (1): > mm/tlbbatch: Introduce arch_tlbbatch_should_defer() > > Barry Song (3): > Revert "Documentation/features: mark BATCHED_UNMAP_TLB_FLUSH doesn't > apply to ARM64" > mm: rmap: Extend tlbbatch APIs to fit new platforms > arm64: support batched/deferred tlb shootdown during page reclamation > > Documentation/features/arch-support.txt | 1 - > .../features/vm/TLB/arch-support.txt | 2 +- > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/tlbbatch.h | 12 ++++++++ > arch/arm64/include/asm/tlbflush.h | 28 +++++++++++++++++-- > arch/x86/include/asm/tlbflush.h | 15 +++++++++- > mm/rmap.c | 19 +++++-------- > 7 files changed, 61 insertions(+), 17 deletions(-) > create mode 100644 arch/arm64/include/asm/tlbbatch.h >
