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[109.43.176.14]) by smtp.gmail.com with ESMTPSA id m4-20020a5d6a04000000b0030aea925fbesm1104766wru.50.2023.06.02.02.24.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Jun 2023 02:24:01 -0700 (PDT) Message-ID: Date: Fri, 2 Jun 2023 11:24:00 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: Big TCG slowdown when using zstd with aarch64 Content-Language: en-US To: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Juan Quintela Cc: qemu-devel@nongnu.org, peter.maydell@linaro.org, Richard Henderson , Peter Xu References: <87y1l2rixp.fsf@secure.mitica> From: Thomas Huth In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.166, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-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 02/06/2023 11.10, Daniel P. Berrangé wrote: ... > IMHO this feels like just another example of compression being largely > useless. The CPU overhead of compression can't keep up with the guest > dirty workload, making the supposedly network bandwidth saving irrelevant. Has anybody ever shown that there is a benefit in some use cases with compression? ... if not, we should maybe deprecate this feature and remove it in a couple of releases if nobody complains. That would mean less code to maintain, less testing effort, and likely no disadvantages for the users. Thomas