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Thu, 15 May 2025 18:49:18 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEq0yLyJlb9jLXdJUK/iTM5SkvvqpnHKnIGZzbRXgNY7VOfaIY+PiCM4oyzQjgQuSdalsuTKjUThDUpEMZSmGA= X-Received: by 2002:a17:90b:1b4a:b0:30e:77bf:6139 with SMTP id 98e67ed59e1d1-30e7d4ebdcbmr1749994a91.5.1747360158435; Thu, 15 May 2025 18:49:18 -0700 (PDT) MIME-Version: 1.0 References: <20250507184647.15580-1-jonah.palmer@oracle.com> <8c465eb3-2db9-47ab-b949-e19a176a5fde@oracle.com> In-Reply-To: <8c465eb3-2db9-47ab-b949-e19a176a5fde@oracle.com> From: Jason Wang Date: Fri, 16 May 2025 09:49:07 +0800 X-Gm-Features: AX0GCFuGzVXRxARQd2NUc-xSZpvP3gWvY7HBKPZVQQFAnUnqxbhu--jQq2EWb7s Message-ID: Subject: Re: [PATCH v4 0/7] Move memory listener register to vhost_vdpa_init To: Si-Wei Liu Cc: Eugenio Perez Martin , Jonah Palmer , qemu-devel@nongnu.org, peterx@redhat.com, mst@redhat.com, lvivier@redhat.com, dtatulea@nvidia.com, leiyang@redhat.com, parav@mellanox.com, sgarzare@redhat.com, lingshan.zhu@intel.com, boris.ostrovsky@oracle.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.133.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -37 X-Spam_score: -3.8 X-Spam_bar: --- X-Spam_report: (-3.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.686, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 Thu, May 15, 2025 at 8:17=E2=80=AFAM Si-Wei Liu = wrote: > > Hi Eugenio, > > On 5/14/2025 8:49 AM, Eugenio Perez Martin wrote: > > On Wed, May 7, 2025 at 8:47=E2=80=AFPM Jonah Palmer wrote: > >> Current memory operations like pinning may take a lot of time at the > >> destination. Currently they are done after the source of the migratio= n is > >> stopped, and before the workload is resumed at the destination. This = is a > >> period where neigher traffic can flow, nor the VM workload can continu= e > >> (downtime). > >> > >> We can do better as we know the memory layout of the guest RAM at the > >> destination from the moment that all devices are initializaed. So > >> moving that operation allows QEMU to communicate the kernel the maps > >> while the workload is still running in the source, so Linux can start > >> mapping them. > >> > >> As a small drawback, there is a time in the initialization where QEMU > >> cannot respond to QMP etc. By some testing, this time is about > >> 0.2seconds. This may be further reduced (or increased) depending on t= he > >> vdpa driver and the platform hardware, and it is dominated by the cost > >> of memory pinning. > >> > >> This matches the time that we move out of the called downtime window. > >> The downtime is measured as checking the trace timestamp from the mome= nt > >> the source suspend the device to the moment the destination starts the > >> eight and last virtqueue pair. For a 39G guest, it goes from ~2.2526 > >> secs to 2.0949. > >> > > Hi Jonah, > > > > Could you update this benchmark? I don't think it changed a lot but > > just to be as updated as possible. > Jonah is off this week and will be back until next Tuesday, but I recall > he indeed did some downtime test with VM with 128GB memory before taking > off, which shows obvious improvement from around 10 seconds to 5.8 > seconds after applying this series. Since this is related to update on > the cover letter, would it be okay for you and Jason to ack now and then > proceed to Michael for upcoming merge? I will go through the series. Thanks