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[198.0.60.179]) by smtp.gmail.com with ESMTPSA id r15sm8426605pfh.81.2019.11.22.09.37.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Nov 2019 09:37:12 -0800 (PST) Date: Fri, 22 Nov 2019 09:37:12 -0800 From: John Fastabend To: Alexei Starovoitov , davem@davemloft.net Cc: daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com Message-ID: <5dd81cc8275d3_15482ad476a405b890@john-XPS-13-9370.notmuch> In-Reply-To: <20191122011515.255371-1-ast@kernel.org> References: <20191122011515.255371-1-ast@kernel.org> Subject: RE: [PATCH bpf-next] selftests/bpf: Add BPF trampoline performance test Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Alexei Starovoitov wrote: > Add a test that benchmarks different ways of attaching BPF program to a kernel function. > Here are the results for 2.4Ghz x86 cpu on a kernel without mitigations: > $ ./test_progs -n 49 -v|grep events > task_rename base 2743K events per sec > task_rename kprobe 2419K events per sec > task_rename kretprobe 1876K events per sec > task_rename raw_tp 2578K events per sec > task_rename fentry 2710K events per sec > task_rename fexit 2685K events per sec > > On a kernel with retpoline: > $ ./test_progs -n 49 -v|grep events > task_rename base 2401K events per sec > task_rename kprobe 1930K events per sec > task_rename kretprobe 1485K events per sec > task_rename raw_tp 2053K events per sec > task_rename fentry 2351K events per sec > task_rename fexit 2185K events per sec > > All 5 approaches: > - kprobe/kretprobe in __set_task_comm() > - raw tracepoint in trace_task_rename() > - fentry/fexit in __set_task_comm() > are roughly equivalent. > > __set_task_comm() by itself is quite fast, so any extra instructions add up. > Until BPF trampoline was introduced the fastest mechanism was raw tracepoint. > kprobe via ftrace was second best. kretprobe is slow due to trap. New > fentry/fexit methods via BPF trampoline are clearly the fastest and the > difference is more pronounced with retpoline on, since BPF trampoline doesn't > use indirect jumps. > > Signed-off-by: Alexei Starovoitov > --- > .../selftests/bpf/prog_tests/test_overhead.c | 142 ++++++++++++++++++ > .../selftests/bpf/progs/test_overhead.c | 43 ++++++ > 2 files changed, 185 insertions(+) > create mode 100644 tools/testing/selftests/bpf/prog_tests/test_overhead.c > create mode 100644 tools/testing/selftests/bpf/progs/test_overhead.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/test_overhead.c b/tools/testing/selftests/bpf/prog_tests/test_overhead.c > new file mode 100644 > index 000000000000..c32aa28bd93f Acked-by: John Fastabend