On Tue, Apr 30, 2024 at 4:48 PM Puranjay Mohan <puranjay@xxxxxxxxxx> wrote: > > Inline calls to bpf_get_smp_processor_id() helper in the JIT by emitting > a read from struct thread_info. The SP_EL0 system register holds the > pointer to the task_struct and thread_info is the first member of this > struct. We can read the cpu number from the thread_info. > > Here is how the ARM64 JITed assembly changes after this commit: > > ARM64 JIT > =========== > > BEFORE AFTER > -------- ------- > > int cpu = bpf_get_smp_processor_id(); int cpu = bpf_get_smp_processor_id(); > > mov x10, #0xfffffffffffff4d0 mrs x10, sp_el0 > movk x10, #0x802b, lsl #16 ldr w7, [x10, #24] > movk x10, #0x8000, lsl #32 > blr x10 > add x7, x0, #0x0 > > Performance improvement using benchmark[1] > > ./benchs/run_bench_trigger.sh glob-arr-inc arr-inc hash-inc > > +---------------+-------------------+-------------------+--------------+ > | Name | Before | After | % change | > |---------------+-------------------+-------------------+--------------| > | glob-arr-inc | 23.380 ± 1.675M/s | 25.893 ± 0.026M/s | + 10.74% | > | arr-inc | 23.928 ± 0.034M/s | 25.213 ± 0.063M/s | + 5.37% | > | hash-inc | 12.352 ± 0.005M/s | 12.609 ± 0.013M/s | + 2.08% | > +---------------+-------------------+-------------------+--------------+ > > [1] https://github.com/anakryiko/linux/commit/8dec900975ef > > Signed-off-by: Puranjay Mohan <puranjay@xxxxxxxxxx> > --- > arch/arm64/include/asm/insn.h | 1 + > arch/arm64/net/bpf_jit.h | 2 ++ > arch/arm64/net/bpf_jit_comp.c | 23 +++++++++++++++++++++++ > 3 files changed, 26 insertions(+) > Nice improvements! I suggest combining arm64 and risc-v patches together when resubmitting, so that we can land them in one go. This one depends on RISC-V patches landing first to avoid a warning about global function without a prototype, right? Please add my ack as well Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h > index 8de0e39b29f3..8c0a36f72d6f 100644 > --- a/arch/arm64/include/asm/insn.h > +++ b/arch/arm64/include/asm/insn.h > @@ -138,6 +138,7 @@ enum aarch64_insn_special_register { > enum aarch64_insn_system_register { > AARCH64_INSN_SYSREG_TPIDR_EL1 = 0x4684, > AARCH64_INSN_SYSREG_TPIDR_EL2 = 0x6682, > + AARCH64_INSN_SYSREG_SP_EL0 = 0x4208, > }; > > enum aarch64_insn_variant { > diff --git a/arch/arm64/net/bpf_jit.h b/arch/arm64/net/bpf_jit.h > index b627ef7188c7..b22ab2f97a30 100644 > --- a/arch/arm64/net/bpf_jit.h > +++ b/arch/arm64/net/bpf_jit.h > @@ -302,5 +302,7 @@ > aarch64_insn_gen_mrs(Rt, AARCH64_INSN_SYSREG_TPIDR_EL1) > #define A64_MRS_TPIDR_EL2(Rt) \ > aarch64_insn_gen_mrs(Rt, AARCH64_INSN_SYSREG_TPIDR_EL2) > +#define A64_MRS_SP_EL0(Rt) \ > + aarch64_insn_gen_mrs(Rt, AARCH64_INSN_SYSREG_SP_EL0) > > #endif /* _BPF_JIT_H */ > diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c > index ed8f9716d9d5..8084f3e61e0b 100644 > --- a/arch/arm64/net/bpf_jit_comp.c > +++ b/arch/arm64/net/bpf_jit_comp.c > @@ -1215,6 +1215,19 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, > const u8 r0 = bpf2a64[BPF_REG_0]; > bool func_addr_fixed; > u64 func_addr; > + u32 cpu_offset = offsetof(struct thread_info, cpu); > + > + /* Implement helper call to bpf_get_smp_processor_id() inline */ > + if (insn->src_reg == 0 && insn->imm == BPF_FUNC_get_smp_processor_id) { > + emit(A64_MRS_SP_EL0(tmp), ctx); > + if (is_lsi_offset(cpu_offset, 2)) { > + emit(A64_LDR32I(r0, tmp, cpu_offset), ctx); > + } else { > + emit_a64_mov_i(1, tmp2, cpu_offset, ctx); > + emit(A64_LDR32(r0, tmp, tmp2), ctx); > + } > + break; > + } > > ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass, > &func_addr, &func_addr_fixed); > @@ -2541,6 +2554,16 @@ bool bpf_jit_supports_percpu_insn(void) > return true; > } > > +bool bpf_jit_inlines_helper_call(s32 imm) > +{ > + switch (imm) { > + case BPF_FUNC_get_smp_processor_id: > + return true; > + } > + > + return false; same minor nit to use default: return false inside the switch itself > +} > + > void bpf_jit_free(struct bpf_prog *prog) > { > if (prog->jited) { > -- > 2.40.1 >
