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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7be61480541sm565914585a.42.2025.01.21.07.50.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jan 2025 07:50:31 -0800 (PST) Date: Tue, 21 Jan 2025 10:50:29 -0500 From: Peter Xu To: Prasad Pandit Cc: qemu-devel@nongnu.org, farosas@suse.de, berrange@redhat.com, Prasad Pandit Subject: Re: [PATCH v3 0/4] Allow to enable multifd and postcopy migration together Message-ID: References: <20250121131032.1611245-1-ppandit@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250121131032.1611245-1-ppandit@redhat.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -51 X-Spam_score: -5.2 X-Spam_bar: ----- X-Spam_report: (-5.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.996, 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=-0.086, 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 Tue, Jan 21, 2025 at 06:40:28PM +0530, Prasad Pandit wrote: > From: Prasad Pandit > > Hello, > > * Currently Multifd and Postcopy migration can not be used together. > QEMU shows "Postcopy is not yet compatible with multifd" message. > > When migrating guests with large (100's GB) RAM, Multifd threads > help to accelerate migration, but inability to use it with the > Postcopy mode delays guest start up on the destination side. > > * This patch series allows to enable both Multifd and Postcopy > migration together. Precopy and Multifd threads work during > the initial guest (RAM) transfer. When migration moves to the > Postcopy phase, Multifd threads are restrained and the Postcopy > threads start to request pages from the source side. > > * This series removes magic value (4-bytes) introduced in the > previous series for the Postcopy channel. And refactoring of > the 'ram_save_target_page' function is made independent of > the multifd & postcopy change. > > * This series passes all existing 'tests/qtest/migration/*' test > cases and adds a new one to enable multifd channels with postcopy > migration. > > v2: https://lore.kernel.org/qemu-devel/20241129122256.96778-1-ppandit@redhat.com/T/#u > v1: https://lore.kernel.org/qemu-devel/20241126115748.118683-1-ppandit@redhat.com/T/#u > v0: https://lore.kernel.org/qemu-devel/20241029150908.1136894-1-ppandit@redhat.com/T/#u Another comment for the cover letter (besides the test request): please consider adding some changelog into cover letter whenever possible. Normally we don't suggest a changelog only if the wholeset has been drastically rewritten. Otherwise having a changelog would help people understand what has happened between the versions. Thanks, -- Peter Xu