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Fri, 24 Apr 2026 07:06:07 -0700 (PDT) X-Received: by 2002:a05:6830:2b0a:b0:7d7:fd71:f2e4 with SMTP id 46e09a7af769-7dc9518becbmr19395253a34.14.1777039566566; Fri, 24 Apr 2026 07:06:06 -0700 (PDT) Received: from x1.local ([142.189.10.167]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8b02ac7d4e6sm185486416d6.20.2026.04.24.07.06.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Apr 2026 07:06:05 -0700 (PDT) Date: Fri, 24 Apr 2026 10:06:04 -0400 From: Peter Xu To: Samuel Zhang Cc: qemu-devel@nongnu.org, farosas@suse.de, lizhijian@fujitsu.com, eblake@redhat.com, armbru@redhat.com, Emily.Deng@amd.com, Victor.Zhao@amd.com, PengJu.Zhou@amd.com, Qing.Ma@amd.com Subject: Re: [PATCH v5] migration/rdma: add x-rdma-chunk-size parameter Message-ID: References: <20260413035703.2602065-1-guoqing.zhang@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260413035703.2602065-1-guoqing.zhang@amd.com> 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-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: qemu development 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 Mon, Apr 13, 2026 at 11:57:03AM +0800, Samuel Zhang wrote: > The default 1MB RDMA chunk size causes slow live migration because > each chunk triggers a write_flush (ibv_post_send). For 8GB RAM, > 1MB chunk size produces ~15000 flushes vs ~3700 with 1024MB chunk size. > > Add x-rdma-chunk-size parameter to configure the RDMA chunk size for > faster migration. > Usage: `migrate_set_parameter x-rdma-chunk-size 1024M` > > Performance with RDMA live migration of 8GB RAM VM: > > | x-rdma-chunk-size (B) | time (s) | throughput (MB/s) | > |-----------------------|----------|-------------------| > | 1M (default) | 37.915 | 1,007 | > | 32M | 17.880 | 2,260 | > | 1024M | 4.368 | 17,529 | > > Signed-off-by: Samuel Zhang > Acked-by: Markus Armbruster > Acked-by: Li Zhijian > Tested-by: Li Zhijian Doesn't apply anymore.. Samuel, could you rebase to this branch and resend (the major diff is Fabiano's recent pull; it'll land master branch too in a few days)? https://gitlab.com/peterx/qemu/-/tree/next Thanks, -- Peter Xu