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Tue, 18 Aug 2026 04:57:11 -0700 (PDT) Received: from [10.3.188.167] ([61.213.176.9]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39531e84244sm8670836a91.6.2026.08.18.04.57.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Aug 2026 04:57:10 -0700 (PDT) Message-ID: <4d0d08d3-ad6e-4de3-85b8-587b70286b04@gmail.com> Date: Tue, 18 Aug 2026 19:57:06 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/10] migration/rdma: Remove unregister code To: Peter Xu , qemu-devel@nongnu.org Cc: Li Zhijian , Samuel Zhang , Fabiano Rosas , Jack Wang , Juraj Marcin , Yanfei Xu References: <20260817202424.2901438-1-peterx@redhat.com> <20260817202424.2901438-3-peterx@redhat.com> From: Yanfei Xu In-Reply-To: <20260817202424.2901438-3-peterx@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::1034; envelope-from=isyanfei.xu@gmail.com; helo=mail-pj1-x1034.google.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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: 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 Hi Peter, No objection to removing the dead code — it clearly never worked I do have one question about the direction, though. The removed logic was the only in-tree attempt at MR unregistration for the non-pin-all path. Without it, registered MRs grow monotonically over a migration, and with large, widely-spread dirty memory over chunks the accumulated MR metadata (user + kernel) can cost more than pin-all and even perform worse — which rather defeats the purpose of not pinning everything. do we still intend to keep and improve the non-pin-all path going forward? If so, some form of dynamic MR unregistration will eventually be needed and it might be worth keeping this code，or at least leaving a TODO to mark the gap? Thanks, Yanfei On 2026/8/18 04:24, Peter Xu wrote: > The unregister code was there since the first commit RDMA migration was > merged, but it was never functioning. Remove the dead code. > > Since the two control messages are the last ones, we don't even need to > worry about compatibility of legacy RDMA control commands, we can directly > remove the messages too. > > As a side effect, this patch closes a report by removing the code > completely. > > Reported-by: Tristan (@TristanInSec) > Closes:https://gitlab.com/qemu-project/qemu/-/work_items/4003 > Signed-off-by: Peter Xu