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Fri, 21 Apr 2023 14:54:56 -0700 (PDT) Received: from redhat.com ([31.4.212.142]) by smtp.gmail.com with ESMTPSA id p17-20020a056000019100b002fda1b12a0bsm5319619wrx.2.2023.04.21.14.54.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Apr 2023 14:54:56 -0700 (PDT) From: Juan Quintela To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Paolo Bonzini , Thomas Huth , John Snow , Li Zhijian , Stefan Hajnoczi , Zhang Chen , Laurent Vivier Subject: Re: [PATCH v2 2/6] tests/qtests: remove migration test iterations config In-Reply-To: <20230421171411.566300-3-berrange@redhat.com> ("Daniel P. =?utf-8?Q?Berrang=C3=A9=22's?= message of "Fri, 21 Apr 2023 18:14:07 +0100") References: <20230421171411.566300-1-berrange@redhat.com> <20230421171411.566300-3-berrange@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) Date: Fri, 21 Apr 2023 23:54:55 +0200 Message-ID: <87r0scgats.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.129.124; envelope-from=quintela@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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-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: , Reply-To: quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9 wrote: > The 'unsigned int interations' config for migration is somewhat > overkill. Most tests don't set it, and a value of '0' is treated > as equivalent to '1'. The only test that does set it, xbzrle, > used a value of '2'. > > This setting, however, only relates to the migration iterations > that take place prior to allowing convergence. IOW, on top of > this iteration count, there is always at least 1 further migration > iteration done to deal with pages that are dirtied during the > previous iteration(s). > > IOW, even with iterations=3D=3D1, the xbzrle test will be running for > a minimum of 2 iterations. With this in mind we can simplify the > code and just get rid of the special case. Perhaps the old code was already wrong, but we need at least three iterations for the xbzrle test: - 1st iteration: xbzrle is not used, nothing is on cache. - 2nd iteration: pages are put into cache, no xbzrle is used because there is no previous page. - 3rd iteration: We really use xbzrle now against the copy of the previous iterations. And yes, this should be commented somewhere. Later, Juan.