Puranjay Mohan <puranjay12@xxxxxxxxx> writes: > 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 (2): > riscv: Extend patch_text_nosync() for multiple pages > bpf, riscv: use prog pack allocator in the BPF JIT I get a hang for "test_tag", but it's not directly related to your series, but rather "remote fence.i". | rcu: INFO: rcu_sched detected stalls on CPUs/tasks: | rcu: 0-....: (1400 ticks this GP) idle=d5e4/1/0x4000000000000000 softirq=5542/5542 fqs=1862 | rcu: (detected by 1, t=5252 jiffies, g=10253, q=195 ncpus=4) | Task dump for CPU 0: | task:kworker/0:5 state:R running task stack:0 pid:319 ppid:2 flags:0x00000008 | Workqueue: events bpf_prog_free_deferred | Call Trace: | [<ffffffff80cbc444>] __schedule+0x2d0/0x940 | watchdog: BUG: soft lockup - CPU#0 stuck for 21s! [kworker/0:5:319] | Modules linked in: nls_iso8859_1 drm fuse i2c_core drm_panel_orientation_quirks backlight dm_mod configfs ip_tables x_tables | CPU: 0 PID: 319 Comm: kworker/0:5 Not tainted 6.5.0-rc5 #1 | Hardware name: riscv-virtio,qemu (DT) | Workqueue: events bpf_prog_free_deferred | epc : __sbi_rfence_v02_call.isra.0+0x74/0x11a | ra : __sbi_rfence_v02+0xda/0x1a4 | epc : ffffffff8000ab4c ra : ffffffff8000accc sp : ff20000001c9bbd0 | gp : ffffffff82078c48 tp : ff600000888e6a40 t0 : ff20000001c9bd44 | t1 : 0000000000000000 t2 : 0000000000000040 s0 : ff20000001c9bbf0 | s1 : 0000000000000010 a0 : 0000000000000000 a1 : 0000000000000000 | a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 | a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000052464e43 | s2 : 000000000000ffff s3 : 00000000ffffffff s4 : ffffffff81667528 | s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000 | s8 : 0000000000000001 s9 : 0000000000000003 s10: 0000000000000040 | s11: ffffffff8207d240 t3 : 000000000000000f t4 : 000000000000002a | t5 : ff600000872df140 t6 : ffffffff81e26828 | status: 0000000200000120 badaddr: 0000000000000000 cause: 8000000000000005 | [<ffffffff8000ab4c>] __sbi_rfence_v02_call.isra.0+0x74/0x11a | [<ffffffff8000accc>] __sbi_rfence_v02+0xda/0x1a4 | [<ffffffff8000a886>] sbi_remote_fence_i+0x1e/0x26 | [<ffffffff8000cee2>] flush_icache_all+0x1a/0x48 | [<ffffffff80007736>] patch_text_nosync+0x6c/0x8c | [<ffffffff8000f0f8>] bpf_arch_text_invalidate+0x62/0xac | [<ffffffff8016c538>] bpf_prog_pack_free+0x9c/0x1b2 | [<ffffffff8016c84a>] bpf_jit_binary_pack_free+0x20/0x4a | [<ffffffff8000f198>] bpf_jit_free+0x56/0x9e | [<ffffffff8016b43a>] bpf_prog_free_deferred+0x15a/0x182 | [<ffffffff800576c4>] process_one_work+0x1b6/0x3d6 | [<ffffffff80057d52>] worker_thread+0x84/0x378 | [<ffffffff8005fc2c>] kthread+0xe8/0x108 | [<ffffffff80003ffa>] ret_from_fork+0xe/0x20 I'm digging into that now, and I would appreciate if you could run the test_tag on VF2 or similar (I'm missing that HW). It seems like we're hitting a bug with this series, so let's try to figure out where the problems is, prior merging it. Björn
