On Fri, Aug 25, 2023 at 10:06 AM Pu Lehui <pulehui@xxxxxxxxxx> wrote: > > > > On 2023/8/24 21:31, Puranjay Mohan wrote: > > Changes in v1 -> v2: > > 1. Implement a new function patch_text_set_nosync() to be used in bpf_arch_text_invalidate(). > > The implementation in v1 called patch_text_nosync() in a loop and it was bad as it would > > call flush_icache_range() for every word making it really slow. This was found by running > > the test_tag selftest which would take forever to complete. > > > > Here is some data to prove the V2 fixes the problem: > > > > Without this series: > > root@rv-selftester:~/src/kselftest/bpf# time ./test_tag > > test_tag: OK (40945 tests) > > > > real 7m47.562s > > user 0m24.145s > > sys 6m37.064s > > > > With this series applied: > > root@rv-selftester:~/src/selftest/bpf# time ./test_tag > > test_tag: OK (40945 tests) > > > > real 7m29.472s > > user 0m25.865s > > sys 6m18.401s > > > > BPF programs currently consume a page each on RISCV. For systems with many BPF > > programs, this adds significant pressure to instruction TLB. High iTLB pressure > > usually causes slow down for the whole system. > > > > Song Liu introduced the BPF prog pack allocator[1] to mitigate the above issue. > > It packs multiple BPF programs into a single huge page. It is currently only > > enabled for the x86_64 BPF JIT. > > > > I enabled this allocator on the ARM64 BPF JIT[2]. It is being reviewed now. > > > > This patch series enables the BPF prog pack allocator for the RISCV BPF JIT. > > This series needs a patch[3] from the ARM64 series to work. > > Is there a new version for arm64 currently? Maybe we could submit this > patch first as a separate patch to avoid dependencies. Okay, I will send that patch as a separate patch because it is needed for all architectures. > > > > > ====================================================== > > Performance Analysis of prog pack allocator on RISCV64 > > ====================================================== > > > > Test setup: > > =========== > > > > Host machine: Debian GNU/Linux 11 (bullseye) > > Qemu Version: QEMU emulator version 8.0.3 (Debian 1:8.0.3+dfsg-1) > > u-boot-qemu Version: 2023.07+dfsg-1 > > opensbi Version: 1.3-1 > > > > To test the performance of the BPF prog pack allocator on RV, a stresser > > tool[4] linked below was built. This tool loads 8 BPF programs on the system and > > triggers 5 of them in an infinite loop by doing system calls. > > > > The runner script starts 20 instances of the above which loads 8*20=160 BPF > > programs on the system, 5*20=100 of which are being constantly triggered. > > The script is passed a command which would be run in the above environment. > > > > The script was run with following perf command: > > ./run.sh "perf stat -a \ > > -e iTLB-load-misses \ > > -e dTLB-load-misses \ > > -e dTLB-store-misses \ > > -e instructions \ > > --timeout 60000" > > > > The output of the above command is discussed below before and after enabling the > > BPF prog pack allocator. > > > > The tests were run on qemu-system-riscv64 with 8 cpus, 16G memory. The rootfs > > was created using Bjorn's riscv-cross-builder[5] docker container linked below. > > > > Results > > ======= > > > > Before enabling prog pack allocator: > > ------------------------------------ > > > > Performance counter stats for 'system wide': > > > > 4939048 iTLB-load-misses > > 5468689 dTLB-load-misses > > 465234 dTLB-store-misses > > 1441082097998 instructions > > > > 60.045791200 seconds time elapsed > > > > After enabling prog pack allocator: > > ----------------------------------- > > > > Performance counter stats for 'system wide': > > > > 3430035 iTLB-load-misses > > 5008745 dTLB-load-misses > > 409944 dTLB-store-misses > > 1441535637988 instructions > > > > 60.046296600 seconds time elapsed > > > > Improvements in metrics > > ======================= > > > > It was expected that the iTLB-load-misses would decrease as now a single huge > > page is used to keep all the BPF programs compared to a single page for each > > program earlier. > > > > -------------------------------------------- > > The improvement in iTLB-load-misses: -30.5 % > > -------------------------------------------- > > > > I repeated this expriment more than 100 times in different setups and the > > improvement was always greater than 30%. > > > > This patch series is boot tested on the Starfive VisionFive 2 board[6]. > > The performance analysis was not done on the board because it doesn't > > expose iTLB-load-misses, etc. The stresser program was run on the board to test > > the loading and unloading of BPF programs > > > > [1] https://lore.kernel.org/bpf/20220204185742.271030-1-song@xxxxxxxxxx/ > > [2] https://lore.kernel.org/all/20230626085811.3192402-1-puranjay12@xxxxxxxxx/ > > [3] https://lore.kernel.org/all/20230626085811.3192402-2-puranjay12@xxxxxxxxx/ > > [4] https://github.com/puranjaymohan/BPF-Allocator-Bench > > [5] https://github.com/bjoto/riscv-cross-builder > > [6] https://www.starfivetech.com/en/site/boards > > > > Puranjay Mohan (3): > > riscv: extend patch_text_nosync() for multiple pages > > riscv: implement a memset like function for text > > bpf, riscv: use prog pack allocator in the BPF JIT > > > > arch/riscv/include/asm/patch.h | 1 + > > arch/riscv/kernel/patch.c | 113 ++++++++++++++++++++++++++++++-- > > arch/riscv/net/bpf_jit.h | 3 + > > arch/riscv/net/bpf_jit_comp64.c | 56 +++++++++++++--- > > arch/riscv/net/bpf_jit_core.c | 113 +++++++++++++++++++++++++++----- > > 5 files changed, 255 insertions(+), 31 deletions(-) > > -- Thanks and Regards Yours Truly, Puranjay Mohan
