Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2 0/4] mm: arm64: bring up BATCHED_UNMAP_TLB_FLUSH | From | Xin Hao <> | Date | Thu, 14 Jul 2022 11:28:56 +0800 |
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Hi barry.
I do some test on Kunpeng arm64 machine use Unixbench.
The test result as below.
One core, we can see the performance improvement above +30%. ./Run -c 1 -i 1 shell1 w/o System Benchmarks Partial Index BASELINE RESULT INDEX Shell Scripts (1 concurrent) 42.4 5481.0 1292.7 ======== System Benchmarks Index Score (Partial Only) 1292.7
w/ System Benchmarks Partial Index BASELINE RESULT INDEX Shell Scripts (1 concurrent) 42.4 6974.6 1645.0 ======== System Benchmarks Index Score (Partial Only) 1645.0
But with whole cores, there have little performance degradation above -5%
./Run -c 96 -i 1 shell1 w/o Shell Scripts (1 concurrent) 80765.5 lpm (60.0 s, 1 samples) System Benchmarks Partial Index BASELINE RESULT INDEX Shell Scripts (1 concurrent) 42.4 80765.5 19048.5 ======== System Benchmarks Index Score (Partial Only) 19048.5
w Shell Scripts (1 concurrent) 76333.6 lpm (60.0 s, 1 samples) System Benchmarks Partial Index BASELINE RESULT INDEX Shell Scripts (1 concurrent) 42.4 76333.6 18003.2 ======== System Benchmarks Index Score (Partial Only) 18003.2
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After discuss with you, and do some changes in the patch.
ndex a52381a680db..1ecba81f1277 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -727,7 +727,11 @@ void flush_tlb_batched_pending(struct mm_struct *mm) int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
if (pending != flushed) { +#ifdef CONFIG_ARCH_HAS_MM_CPUMASK flush_tlb_mm(mm); +#else + dsb(ish); +#endif /* * If the new TLB flushing is pending during flushing, leave * mm->tlb_flush_batched as is, to avoid losing flushing. there have a performance improvement with whole cores, above +30%
./Run -c 96 -i 1 shell1 96 CPUs in system; running 96 parallel copies of tests
Shell Scripts (1 concurrent) 109229.0 lpm (60.0 s, 1 samples) System Benchmarks Partial Index BASELINE RESULT INDEX Shell Scripts (1 concurrent) 42.4 109229.0 25761.6 ======== System Benchmarks Index Score (Partial Only) 25761.6
Tested-by: Xin Hao<xhao@linux.alibaba.com>
Looking forward to your next version patch.
On 7/11/22 11:46 AM, Barry Song wrote: > 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. > > > -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, Yicong, Peter, Dave and Nadav for your testing or reviewing > , and comments. > > -v1: > https://lore.kernel.org/lkml/20220707125242.425242-1-21cnbao@gmail.com/ > > Barry Song (4): > Revert "Documentation/features: mark BATCHED_UNMAP_TLB_FLUSH doesn't > apply to ARM64" > mm: rmap: Allow platforms without mm_cpumask to defer TLB flush > 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/arm/Kconfig | 1 + > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/tlbbatch.h | 12 ++++++++++ > arch/arm64/include/asm/tlbflush.h | 23 +++++++++++++++++-- > arch/loongarch/Kconfig | 1 + > arch/mips/Kconfig | 1 + > arch/openrisc/Kconfig | 1 + > arch/powerpc/Kconfig | 1 + > arch/riscv/Kconfig | 1 + > arch/s390/Kconfig | 1 + > arch/um/Kconfig | 1 + > arch/x86/Kconfig | 1 + > arch/x86/include/asm/tlbflush.h | 3 ++- > mm/Kconfig | 3 +++ > mm/rmap.c | 14 +++++++---- > 17 files changed, 59 insertions(+), 9 deletions(-) > create mode 100644 arch/arm64/include/asm/tlbbatch.h > -- Best Regards! Xin Hao
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