On Thu, May 15, 2025 at 8:17 AM Si-Wei Liu <si-wei....@oracle.com> wrote: > > Hi Eugenio, > > On 5/14/2025 8:49 AM, Eugenio Perez Martin wrote: > > On Wed, May 7, 2025 at 8:47 PM Jonah Palmer <jonah.pal...@oracle.com> wrote: > >> Current memory operations like pinning may take a lot of time at the > >> destination. Currently they are done after the source of the migration 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 continue > >> (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 the > >> 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 moment > >> 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
