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Fri, 16 Feb 2024 03:05:24 -0800 (PST) Received: from draig (localhost [IPv6:::1]) by draig.lan (Postfix) with ESMTP id 5CBFD5F7B1; Fri, 16 Feb 2024 11:05:24 +0000 (GMT) From: =?utf-8?Q?Alex_Benn=C3=A9e?= To: Richard Henderson Cc: qemu-devel@nongnu.org, amonakov@ispras.ru, mmromanov@ispras.ru Subject: Re: [RFC PATCH v4 10/10] util/bufferiszero: Add sve acceleration for aarch64 In-Reply-To: <20240215081449.848220-11-richard.henderson@linaro.org> (Richard Henderson's message of "Wed, 14 Feb 2024 22:14:49 -1000") References: <20240215081449.848220-1-richard.henderson@linaro.org> <20240215081449.848220-11-richard.henderson@linaro.org> User-Agent: mu4e 1.11.28; emacs 29.1 Date: Fri, 16 Feb 2024 11:05:24 +0000 Message-ID: <87a5o06557.fsf@draig.linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::32c; envelope-from=alex.bennee@linaro.org; helo=mail-wm1-x32c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Richard Henderson writes: > Signed-off-by: Richard Henderson > --- > > RFC because I've not benchmarked this on real hw, only run it > through qemu for validation. > >=20=20 > +#ifdef CONFIG_SVE_OPT > +static unsigned accel_index; > +static void __attribute__((constructor)) init_accel(void) > +{ > + accel_index =3D (cpuinfo & CPUINFO_SVE ? 2 : 1); > + buffer_is_zero_accel =3D accel_table[accel_index]; > +} This really needs to be: - accel_index =3D (cpuinfo & CPUINFO_SVE ? 2 : 1); + unsigned info =3D cpuinfo_init(); + accel_index =3D (info & CPUINFO_SVE ? 2 : 1); because otherwise you are relying on constructor initialisation order and on the Graviton 3 I built on it wasn't detecting the SVE. With that I get this from "perf record ./tests/unit/test-bufferiszero -m thorough" 51.17% test-bufferisze test-bufferiszero [.] buffer_is_zero_sve 18.92% test-bufferisze test-bufferiszero [.] buffer_is_zero_simd 18.02% test-bufferisze test-bufferiszero [.] buffer_is_zero_int_ge= 256 7.67% test-bufferisze test-bufferiszero [.] buffer_is_zero_ool 4.09% test-bufferisze test-bufferiszero [.] test_1 but as I mentioned before it would be nice to have a proper benchmark for the buffer utils as I'm sure the unit test would be prone to noise. --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro