From 75fe4c0b3e181f5e3b990128013ac192fdfd4012 Mon Sep 17 00:00:00 2001 From: Puranjay Mohan Date: Thu, 2 May 2024 15:18:54 +0000 Subject: bpf, arm64: inline bpf_get_smp_processor_id() helper MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20240502151854.9810-5-puranjay@kernel.org Signed-off-by: Alexei Starovoitov --- arch/arm64/include/asm/insn.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/arm64/include') 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 { -- cgit v1.2.3