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[70.24.86.62]) by smtp.gmail.com with ESMTPSA id ph9-20020a0562144a4900b00605f796d30esm5761492qvb.51.2023.05.31.05.58.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 May 2023 05:58:21 -0700 (PDT) Date: Wed, 31 May 2023 08:58:19 -0400 From: Peter Xu To: "Wang, Wei W" Cc: "quintela@redhat.com" , "Wang, Lei4" , "qemu-devel@nongnu.org" Subject: Re: [PATCH v2 2/2] qtest/migration-tests.c: use "-incoming defer" for postcopy tests Message-ID: References: <20230530090259.189462-1-wei.w.wang@intel.com> <20230530090259.189462-3-wei.w.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.163, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01, T_SPF_TEMPERROR=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 Wed, May 31, 2023 at 10:41:37AM +0000, Wang, Wei W wrote: > On Tuesday, May 30, 2023 10:41 PM, Peter Xu wrote: > > On Tue, May 30, 2023 at 05:02:59PM +0800, Wei Wang wrote: > > > The Postcopy preempt capability requires to be set before incoming > > > starts, so change the postcopy tests to start with deferred incoming > > > and call migrate-incoming after the cap has been set. > > > > > > Signed-off-by: Wei Wang > > > > Hmm.. so we used to do socket_start_incoming_migration_internal() before > > setting the right num for the preempt test, then I'm curious why it wasn't > > failing before this patch when trying to connect with the preempt channel.. > > > > Wei, do you know? > > I think there are two reasons: > #1 "backlog" specifies the number of pending connections. As long as the server > accepts the connections faster than the clients side connecting, connection > will succeed. For the preempt test, it uses only 2 channels, so very likely to not have > pending connections. (This is easier to trigger for the multifd case, e.g. use a much > larger number like 16). > #2 per my tests (on kernel 6.2), the number of pending connections allowed is actually > "backlog + 1", which is 2 in this case. Adding more pending connections will then be > dropped. I'm not sure if " backlog + 1" is true for older versions of kernel, though. Interesting to know, thanks. If there'll be a new version, please consider adding some of those into the commit message. Reviewed-by: Peter Xu -- Peter Xu