Daniel Borkmann <daniel@xxxxxxxxxxxxx> writes: > On 8/29/23 12:06 PM, Björn Töpel wrote: >> 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. > > Palmer, did the riscv PR already go to Linus? > > If not yet, perhaps you could ship this series along with your PR to Linus > during this merge window given the big net PR (incl. bpf) was already merged > yesterday. So from our side only fixes ship to Linus. > > Otherwise we could take it into bpf-next for the next dev cycle if there are > no objections, let us know. Daniel, I'll bring this up on the RISC-V patchwork sync meeting [1] today. [1] https://lore.kernel.org/linux-riscv/mhng-775d4068-6c1e-48a4-a1dc-b4a76ff26bb3@palmer-ri-x1c9a/
