From: "Björn Töpel" <bjorn@kernel.org>
To: Puranjay Mohan <puranjay@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
bpf@vger.kernel.org, linux-riscv@lists.infradead.org,
linux-kernel@vger.kernel.org, Pu Lehui <pulehui@huawei.com>
Cc: puranjay12@gmail.com
Subject: Re: [PATCH bpf-next v2 2/2] riscv, bpf: inline bpf_get_smp_processor_id()
Date: Thu, 02 May 2024 18:19:04 +0200 [thread overview]
Message-ID: <87edakw5jb.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <20240430175834.33152-3-puranjay@kernel.org>
Puranjay Mohan <puranjay@kernel.org> writes:
> Inline the calls to bpf_get_smp_processor_id() in the riscv bpf jit.
>
> RISCV saves the pointer to the CPU's task_struct in the TP (thread
> pointer) register. This makes it trivial to get the CPU's processor id.
> As thread_info is the first member of task_struct, we can read the
> processor id from TP + offsetof(struct thread_info, cpu).
>
> RISCV64 JIT output for `call bpf_get_smp_processor_id`
> ======================================================
>
> Before After
> -------- -------
>
> auipc t1,0x848c ld a5,32(tp)
> jalr 604(t1)
> mv a5,a0
>
> Benchmark using [1] on Qemu.
>
> ./benchs/run_bench_trigger.sh glob-arr-inc arr-inc hash-inc
>
> +---------------+------------------+------------------+--------------+
> | Name | Before | After | % change |
> |---------------+------------------+------------------+--------------|
> | glob-arr-inc | 1.077 ± 0.006M/s | 1.336 ± 0.010M/s | + 24.04% |
> | arr-inc | 1.078 ± 0.002M/s | 1.332 ± 0.015M/s | + 23.56% |
> | hash-inc | 0.494 ± 0.004M/s | 0.653 ± 0.001M/s | + 32.18% |
> +---------------+------------------+------------------+--------------+
>
> NOTE: This benchmark includes changes from this patch and the previous
> patch that implemented the per-cpu insn.
>
> [1] https://github.com/anakryiko/linux/commit/8dec900975ef
>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
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prev parent reply other threads:[~2024-05-02 16:19 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 17:58 [PATCH bpf-next v2 0/2] riscv, bpf: Support per-CPU insn and inline bpf_get_smp_processor_id() Puranjay Mohan
2024-04-30 17:58 ` [PATCH bpf-next v2 1/2] riscv, bpf: add internal-only MOV instruction to resolve per-CPU addrs Puranjay Mohan
2024-05-01 16:39 ` Andrii Nakryiko
2024-05-02 16:18 ` Björn Töpel
2024-05-02 16:20 ` Puranjay Mohan
2024-04-30 17:58 ` [PATCH bpf-next v2 2/2] riscv, bpf: inline bpf_get_smp_processor_id() Puranjay Mohan
2024-04-30 19:18 ` Kumar Kartikeya Dwivedi
2024-05-01 16:46 ` Andrii Nakryiko
2024-05-02 13:16 ` Puranjay Mohan
2024-05-02 16:03 ` Andrii Nakryiko
2024-05-02 16:19 ` Björn Töpel [this message]
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