Changes in V5 => V6: V5: https://lore.kernel.org/all/20230908144320.2474-1-puranjay12@xxxxxxxxx/ 1. Implement a text poke api to reduce code repeatition. 2. Use flush_icache_range() in place of caches_clean_inval_pou() in the functions that modify code. 3. Optimize the bpf_jit_free() by not copying the all instructions on the rw image to the ro_image Changes in V4 => v5: 1. Remove the patch for making prog pack allocator portable as it will come through the RISCV tree[1]. 2. Add a new function aarch64_insn_set() to be used in bpf_arch_text_invalidate() for putting illegal instructions after a program is removed. The earlier implementation of bpf_arch_text_invalidate() was calling aarch64_insn_patch_text_nosync() in a loop and making it slow because each call invalidated the cache. Here is test_tag now: [root@ip-172-31-6-176 bpf]# time ./test_tag test_tag: OK (40945 tests) real 0m19.695s user 0m1.514s sys 0m17.841s test_tag without these patches: [root@ip-172-31-6-176 bpf]# time ./test_tag test_tag: OK (40945 tests) real 0m21.487s user 0m1.647s sys 0m19.106s test_tag in the previous version was really slow > 2 minutes. see [2] 3. Add cache invalidation in aarch64_insn_copy() so other users can call the function without worrying about the cache. Currently only bpf_arch_text_copy() is using it, but there might be more users in the future. Chanes in V3 => V4: Changes only in 3rd patch 1. Fix the I-cache maintenance: Clean the data cache and invalidate the i-Cache only *after* the instructions have been copied to the ROX region. Chanes in V2 => V3: Changes only in 3rd patch 1. Set prog = orig_prog; in the failure path of bpf_jit_binary_pack_finalize() call. 2. Add comments explaining the usage of the offsets in the exception table. Changes in v1 => v2: 1. Make the naming consistent in the 3rd patch: ro_image and image ro_header and header ro_image_ptr and image_ptr 2. Use names dst/src in place of addr/opcode in second patch. 3. Add Acked-by: Song Liu <song@xxxxxxxxxx> in 1st and 2nd patch. BPF programs currently consume a page each on ARM64. 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[3] 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. This patch series enables the BPF prog pack allocator for the ARM64 BPF JIT. ==================================================== Performance Analysis of prog pack allocator on ARM64 ==================================================== To test the performance of the BPF prog pack allocator on ARM64, a stresser tool[4] 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. In the above environment we try to build Python-3.8.4 and try to find different iTLB metrics for the compilation done by gcc-12.2.0. The source code[5] is configured with the following command: ./configure --enable-optimizations --with-ensurepip=install Then the runner script is executed with the following command: ./run.sh "perf stat -e ITLB_WALK,L1I_TLB,INST_RETIRED,iTLB-load-misses -a make -j32" This builds Python while 160 BPF programs are loaded and 100 are being constantly triggered and measures iTLB related metrics. 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-aarch64 with 32 cpus, 4G memory, -machine virt, -cpu host, and -enable-kvm. Results ------- Before enabling prog pack allocator: ------------------------------------ Performance counter stats for 'system wide': 333278635 ITLB_WALK 6762692976558 L1I_TLB 25359571423901 INST_RETIRED 15824054789 iTLB-load-misses 189.029769053 seconds time elapsed After enabling prog pack allocator: ----------------------------------- Performance counter stats for 'system wide': 190333544 ITLB_WALK 6712712386528 L1I_TLB 25278233304411 INST_RETIRED 5716757866 iTLB-load-misses 185.392650561 seconds time elapsed Improvements in metrics ----------------------- Compilation time ---> 1.92% faster iTLB-load-misses/Sec (Less is better) ---> 63.16% decrease ITLB_WALK/1000 INST_RETIRED (Less is better) ---> 42.71% decrease ITLB_Walk/L1I_TLB (Less is better) ---> 42.47% decrease [1] https://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git/commit/?h=for-next&id=20e490adea279d49d57b800475938f5b67926d98 [2] https://lore.kernel.org/all/CANk7y0gcP3dF2mESLp5JN1+9iDfgtiWRFGqLkCgZD6wby1kQOw@xxxxxxxxxxxxxx/ [3] https://lore.kernel.org/bpf/20220204185742.271030-1-song@xxxxxxxxxx/ [4] https://github.com/puranjaymohan/BPF-Allocator-Bench [5] https://www.python.org/ftp/python/3.8.4/Python-3.8.4.tgz Puranjay Mohan (2): arm64: patching: implement text_poke API bpf, arm64: use bpf_prog_pack for memory management arch/arm64/include/asm/patching.h | 2 + arch/arm64/kernel/patching.c | 80 +++++++++++++++++ arch/arm64/net/bpf_jit_comp.c | 139 ++++++++++++++++++++++++------ 3 files changed, 197 insertions(+), 24 deletions(-) -- 2.40.1
