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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-466c405493esm76904421cf.11.2024.12.04.11.10.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Dec 2024 11:10:36 -0800 (PST) Date: Wed, 4 Dec 2024 14:10:24 -0500 From: Peter Xu To: "Maciej S. Szmigiero" Cc: Fabiano Rosas , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eric Blake , Markus Armbruster , Daniel P =?utf-8?B?LiBCZXJyYW5nw6k=?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: Re: [PATCH v3 00/24] =?utf-8?Q?Multifd_?= =?utf-8?B?8J+UgA==?= device state transfer support with VFIO consumer Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -50 X-Spam_score: -5.1 X-Spam_bar: ----- X-Spam_report: (-5.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.999, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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: 2.1.29 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 Sun, Nov 17, 2024 at 08:19:55PM +0100, Maciej S. Szmigiero wrote: > Important note: > 4 VF benchmarks were done with commit 5504a8126115 > ("KVM: Dynamic sized kvm memslots array") and its revert-dependencies > reverted since this seems to improve performance in this VM config if the > multifd transfer is enabled: the downtime performance with this commit > present is 1141 ms enabled / 1730 ms disabled. > > Smaller VF counts actually do seem to benefit from this commit, so it's > likely that in the future adding some kind of a memslot pre-allocation > bit stream message might make sense to avoid this downtime regression for > 4 VF configs (and likely higher VF count too). I'm confused why revert 5504a8126115 could be faster, and it affects as much as 600ms. Also how that effect differs can relevant to num of VFs. Could you share more on this regression? Because if that's problematic we need to fix it, or upstream QEMU (after this series merged) will still not work. -- Peter Xu