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| author | Puranjay Mohan <puranjay@kernel.org> | 2024-05-02 15:18:54 +0000 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2024-05-12 16:54:34 -0700 |
| commit | 75fe4c0b3e181f5e3b990128013ac192fdfd4012 (patch) | |
| tree | fd23f2dc376d2db2d93c1831ad0abae58eb0868e /arch/arm64/include/asm/insn.h | |
| parent | 7a4c32222b0e14349a6311e72bf6ebd3e1d1064b (diff) | |
bpf, arm64: inline bpf_get_smp_processor_id() helper
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@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240502151854.9810-5-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'arch/arm64/include/asm/insn.h')
| -rw-r--r-- | arch/arm64/include/asm/insn.h | 1 |
1 files changed, 1 insertions, 0 deletions
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 { |