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[82.29.237.198]) by smtp.gmail.com with ESMTPSA id x18sm28753676wrw.19.2021.07.22.03.02.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Jul 2021 03:02:16 -0700 (PDT) Date: Thu, 22 Jul 2021 11:02:14 +0100 From: "Dr. David Alan Gilbert" To: richard.henderson@linaro.org Subject: Prefetches in buffer_zero_* Message-ID: MIME-Version: 1.0 User-Agent: Mutt/2.0.7 (2021-05-04) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.459, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, jmario@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Richard, I think you were the last person to fiddle with the prefetching in buffer_zero_avx2 and friends; Joe (cc'd) wondered if explicit prefetching still made sense on modern CPUs, and that their hardware generally figures stuff out better on simple increments. What was your thinking on this, and did you actually measure any improvement? Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK