Messages in this thread | | | From | xhao@linux ... | Subject | Re: [PATCH v2 0/4] mm: arm64: bring up BATCHED_UNMAP_TLB_FLUSH | Date | Sat, 23 Jul 2022 17:22:45 +0800 |
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On 7/20/22 7:18 PM, Barry Song wrote: > On Tue, Jul 19, 2022 at 1:28 AM Yicong Yang <yangyicong@huawei.com> wrote: >> On 2022/7/14 12:51, Barry Song wrote: >>> On Thu, Jul 14, 2022 at 3:29 PM Xin Hao <xhao@linux.alibaba.com> wrote: >>>> 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%. >>> I am really pleased to see the 30%+ improvement on unixbench on single core. >>> >>>> ./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% >>> That is sad as we might get more concurrency between mprotect(), madvise(), >>> mremap(), zap_pte_range() and the deferred tlbi. >>> >>>> ./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 >>>> >>>> ---------------------------------------------------------------------------------------------- >>>> >>>> >>>> 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 >>>> >>> i was guessing the problem might be flush_tlb_batched_pending() >>> so i asked you to change this to verify my guess. >>> >> flush_tlb_batched_pending() looks like the critical path for this issue then the code >> above can mitigate this. >> >> I cannot reproduce this on a 2P 128C Kunpeng920 server. The kernel is based on the >> v5.19-rc6 and unixbench of version 5.1.3. The result of `./Run -c 128 -i 1 shell1` is: >> iter-1 iter-2 iter-3 >> w/o 17708.1 17637.1 17630.1 >> w 17766.0 17752.3 17861.7 >> >> And flush_tlb_batched_pending()isn't the hot spot with the patch: >> 7.00% sh [kernel.kallsyms] [k] ptep_clear_flush >> 4.17% sh [kernel.kallsyms] [k] ptep_set_access_flags >> 2.43% multi.sh [kernel.kallsyms] [k] ptep_clear_flush >> 1.98% sh [kernel.kallsyms] [k] _raw_spin_unlock_irqrestore >> 1.69% sh [kernel.kallsyms] [k] next_uptodate_page >> 1.66% sort [kernel.kallsyms] [k] ptep_clear_flush >> 1.56% multi.sh [kernel.kallsyms] [k] ptep_set_access_flags >> 1.27% sh [kernel.kallsyms] [k] page_counter_cancel >> 1.11% sh [kernel.kallsyms] [k] page_remove_rmap >> 1.06% sh [kernel.kallsyms] [k] perf_event_alloc >> >> Hi Xin Hao, >> >> I'm not sure the test setup as well as the config is same with yours. (96C vs 128C >> should not be the reason I think). Did you check that the 5% is a fluctuation or >> not? It'll be helpful if more information provided for reproducing this issue. >> >> Thanks. > I guess that is because "./Run -c 1 -i 1 shell1" isn't an application > stressed on > memory. Hi Xin, in what kinds of configurations can we reproduce your test > result?
Oh, my fault, I do the test is not based on the lastest upstream kernel, there maybe some impact here, i will do a new test on the lastest kernel.
> As I suppose tlbbatch will mainly affect the performance of user scenarios > which require memory page-out/page-in like reclaiming file/anon pages. > "./Run -c 1 -i 1 shell1" on a system with sufficient free memory won't be > affected by tlbbatch at all, I believe. > > Thanks > Barry
-- Best Regards! Xin Hao
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