Hi, On 2/24/21 2:35 AM, wangyanan (Y) wrote: > Hi Alex, > > On 2021/2/23 23:55, Alexandru Elisei wrote: >> Hi Yanan, >> >> I wanted to review the patches, but unfortunately I get an error when trying to >> apply the first patch in the series: >> >> Applying: KVM: arm64: Move the clean of dcache to the map handler >> error: patch failed: arch/arm64/kvm/hyp/pgtable.c:464 >> error: arch/arm64/kvm/hyp/pgtable.c: patch does not apply >> error: patch failed: arch/arm64/kvm/mmu.c:882 >> error: arch/arm64/kvm/mmu.c: patch does not apply >> Patch failed at 0001 KVM: arm64: Move the clean of dcache to the map handler >> hint: Use 'git am --show-current-patch=diff' to see the failed patch >> When you have resolved this problem, run "git am --continue". >> If you prefer to skip this patch, run "git am --skip" instead. >> To restore the original branch and stop patching, run "git am --abort". >> >> Tried this with Linux tags v5.11-rc1 to v5.11-rc7. It looks like pgtable.c and >> mmu.c from your patch is different than what is found on upstream master. Did you >> use another branch as the base for your patches? > Thanks for your attention. > Indeed, this series was more or less based on the patches I post before (Link: > https://lore.kernel.org/r/20210114121350.123684-4-wangyanan55@xxxxxxxxxx). > And they have already been merged into up-to-data upstream master (commit: > 509552e65ae8287178a5cdea2d734dcd2d6380ab), but not into tags v5.11-rc1 to > v5.11-rc7. > Could you please try the newest upstream master(since commit: > 509552e65ae8287178a5cdea2d734dcd2d6380ab) ? I have tested on my local and no > apply errors occur. That worked for me, thank you for the quick reply. Just to double check, when you run the benchmarks, the before results are for a kernel built from commit 509552e65ae8 ("KVM: arm64: Mark the page dirty only if the fault is handled successfully"), and the after results are with this series on top, right? Thanks, Alex > > Thanks, > > Yanan. > >> Thanks, >> >> Alex >> >> On 2/8/21 11:22 AM, Yanan Wang wrote: >>> Hi, >>> >>> This series makes some efficiency improvement of stage2 page table code, >>> and there are some test results to present the performance changes, which >>> were tested by a kvm selftest [1] that I have post: >>> [1] https://lore.kernel.org/lkml/20210208090841.333724-1-wangyanan55@xxxxxxxxxx/ >>> >>> About patch 1: >>> We currently uniformly clean dcache in user_mem_abort() before calling the >>> fault handlers, if we take a translation fault and the pfn is cacheable. >>> But if there are concurrent translation faults on the same page or block, >>> clean of dcache for the first time is necessary while the others are not. >>> >>> By moving clean of dcache to the map handler, we can easily identify the >>> conditions where CMOs are really needed and avoid the unnecessary ones. >>> As it's a time consuming process to perform CMOs especially when flushing >>> a block range, so this solution reduces much load of kvm and improve the >>> efficiency of creating mappings. >>> >>> Test results: >>> (1) when 20 vCPUs concurrently access 20G ram (all 1G hugepages): >>> KVM create block mappings time: 52.83s -> 3.70s >>> KVM recover block mappings time(after dirty-logging): 52.0s -> 2.87s >>> >>> (2) when 40 vCPUs concurrently access 20G ram (all 1G hugepages): >>> KVM creating block mappings time: 104.56s -> 3.70s >>> KVM recover block mappings time(after dirty-logging): 103.93s -> 2.96s >>> >>> About patch 2, 3: >>> When KVM needs to coalesce the normal page mappings into a block mapping, >>> we currently invalidate the old table entry first followed by invalidation >>> of TLB, then unmap the page mappings, and install the block entry at last. >>> >>> It will cost a lot of time to unmap the numerous page mappings, which means >>> the table entry will be left invalid for a long time before installation of >>> the block entry, and this will cause many spurious translation faults. >>> >>> So let's quickly install the block entry at first to ensure uninterrupted >>> memory access of the other vCPUs, and then unmap the page mappings after >>> installation. This will reduce most of the time when the table entry is >>> invalid, and avoid most of the unnecessary translation faults. >>> >>> Test results based on patch 1: >>> (1) when 20 vCPUs concurrently access 20G ram (all 1G hugepages): >>> KVM recover block mappings time(after dirty-logging): 2.87s -> 0.30s >>> >>> (2) when 40 vCPUs concurrently access 20G ram (all 1G hugepages): >>> KVM recover block mappings time(after dirty-logging): 2.96s -> 0.35s >>> >>> So combined with patch 1, it makes a big difference of KVM creating mappings >>> and recovering block mappings with not much code change. >>> >>> About patch 4: >>> A new method to distinguish cases of memcache allocations is introduced. >>> By comparing fault_granule and vma_pagesize, cases that require allocations >>> from memcache and cases that don't can be distinguished completely. >>> >>> --- >>> >>> Details of test results >>> platform: HiSilicon Kunpeng920 (FWB not supported) >>> host kernel: Linux mainline (v5.11-rc6) >>> >>> (1) performance change of patch 1 >>> cmdline: ./kvm_page_table_test -m 4 -t 2 -g 1G -s 20G -v 20 >>> (20 vcpus, 20G memory, block mappings(granule 1G)) >>> Before patch: KVM_CREATE_MAPPINGS: 52.8338s 52.8327s 52.8336s 52.8255s 52.8303s >>> After patch: KVM_CREATE_MAPPINGS: 3.7022s 3.7031s 3.7028s 3.7012s 3.7024s >>> >>> Before patch: KVM_ADJUST_MAPPINGS: 52.0466s 52.0473s 52.0550s 52.0518s 52.0467s >>> After patch: KVM_ADJUST_MAPPINGS: 2.8787s 2.8781s 2.8785s 2.8742s 2.8759s >>> >>> cmdline: ./kvm_page_table_test -m 4 -t 2 -g 1G -s 20G -v 40 >>> (40 vcpus, 20G memory, block mappings(granule 1G)) >>> Before patch: KVM_CREATE_MAPPINGS: 104.560s 104.556s 104.554s 104.556s 104.550s >>> After patch: KVM_CREATE_MAPPINGS: 3.7011s 3.7103s 3.7005s 3.7024s 3.7106s >>> >>> Before patch: KVM_ADJUST_MAPPINGS: 103.931s 103.936s 103.927s 103.942s 103.927s >>> After patch: KVM_ADJUST_MAPPINGS: 2.9621s 2.9648s 2.9474s 2.9587s 2.9603s >>> >>> (2) performance change of patch 2, 3(based on patch 1) >>> cmdline: ./kvm_page_table_test -m 4 -t 2 -g 1G -s 20G -v 1 >>> (1 vcpu, 20G memory, block mappings(granule 1G)) >>> Before patch: KVM_ADJUST_MAPPINGS: 2.8241s 2.8234s 2.8245s 2.8230s 2.8652s >>> After patch: KVM_ADJUST_MAPPINGS: 0.2444s 0.2442s 0.2423s 0.2441s 0.2429s >>> >>> cmdline: ./kvm_page_table_test -m 4 -t 2 -g 1G -s 20G -v 20 >>> (20 vcpus, 20G memory, block mappings(granule 1G)) >>> Before patch: KVM_ADJUST_MAPPINGS: 2.8787s 2.8781s 2.8785s 2.8742s 2.8759s >>> After patch: KVM_ADJUST_MAPPINGS: 0.3008s 0.3004s 0.2974s 0.2917s 0.2900s >>> >>> cmdline: ./kvm_page_table_test -m 4 -t 2 -g 1G -s 20G -v 40 >>> (40 vcpus, 20G memory, block mappings(granule 1G)) >>> Before patch: KVM_ADJUST_MAPPINGS: 2.9621s 2.9648s 2.9474s 2.9587s 2.9603s >>> After patch: KVM_ADJUST_MAPPINGS: 0.3541s 0.3694s 0.3656s 0.3693s 0.3687s >>> >>> --- >>> >>> Yanan Wang (4): >>> KVM: arm64: Move the clean of dcache to the map handler >>> KVM: arm64: Add an independent API for coalescing tables >>> KVM: arm64: Install the block entry before unmapping the page mappings >>> KVM: arm64: Distinguish cases of memcache allocations completely >>> >>> arch/arm64/include/asm/kvm_mmu.h | 16 ------- >>> arch/arm64/kvm/hyp/pgtable.c | 82 +++++++++++++++++++++----------- >>> arch/arm64/kvm/mmu.c | 39 ++++++--------- >>> 3 files changed, 69 insertions(+), 68 deletions(-) >>> >> .
