Puranjay Mohan <puranjay12@xxxxxxxxx> writes: > Changes in v2 -> v3: > 1. Fix maximum width of code in patches from 80 to 100. [All patches] > 2. Add checks for ctx->ro_insns == NULL. [Patch 3] > 3. Fix check for edge condition where amount of text to set > 2 * pagesize > [Patch 1 and 2] > 4. Add reviewed-by in patches. > 5. Adding results of selftest here: > Using the command: ./test_progs on qemu > Without the series: Summary: 336/3162 PASSED, 56 SKIPPED, 90 FAILED > With this series: Summary: 336/3162 PASSED, 56 SKIPPED, 90 FAILED > > 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. > > ====================================================== > 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 Thank you! For the series: Acked-by: Björn Töpel <bjorn@xxxxxxxxxx> Tested-by: Björn Töpel <bjorn@xxxxxxxxxxxx> @Alexei @Daniel This series depends on a core BPF patch from the Arm series [3]. @Palmer LMK if you have any concerns taking the RISC-V text patching stuff via the BPF tree. Björn
