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Tue, 06 Feb 2024 14:29:20 -0800 (PST) Message-ID: <14b49de5-67d7-46f1-9e15-be60fb925dd3@linaro.org> Date: Wed, 7 Feb 2024 08:29:18 +1000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 4/6] util/bufferiszero: remove useless prefetches Content-Language: en-US To: Alexander Monakov , qemu-devel@nongnu.org Cc: Mikhail Romanov , Paolo Bonzini References: <20240206204809.9859-1-amonakov@ispras.ru> <20240206204809.9859-5-amonakov@ispras.ru> From: Richard Henderson In-Reply-To: <20240206204809.9859-5-amonakov@ispras.ru> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::1034; envelope-from=richard.henderson@linaro.org; helo=mail-pj1-x1034.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 On 2/7/24 06:48, Alexander Monakov wrote: > Use of prefetching in bufferiszero.c is quite questionable: > > - prefetches are issued just a few CPU cycles before the corresponding > line would be hit by demand loads; > > - they are done for simple access patterns, i.e. where hardware > prefetchers can perform better; > > - they compete for load ports in loops that should be limited by load > port throughput rather than ALU throughput. > > Signed-off-by: Alexander Monakov > Signed-off-by: Mikhail Romanov > --- > util/bufferiszero.c | 3 --- > 1 file changed, 3 deletions(-) Reviewed-by: Richard Henderson r~