Chuang Xu <xuchuangxc...@bytedance.com> wrote: > The duration of loading non-iterable vmstate accounts for a significant > portion of downtime (starting with the timestamp of source qemu stop and > ending with the timestamp of target qemu start). Most of the time is spent > committing memory region changes repeatedly. > > This patch packs all the changes to memory region during the period of > loading non-iterable vmstate in a single memory transaction. With the > increase of devices, this patch will greatly improve the performance. > > Here are the test1 results: > test info: > - Host > - Intel(R) Xeon(R) Platinum 8260 CPU > - NVIDIA Mellanox ConnectX-5 > - VM > - 32 CPUs 128GB RAM VM > - 8 16-queue vhost-net device > - 16 4-queue vhost-user-blk device. > > time of loading non-iterable vmstate downtime > before about 150 ms 740+ ms > after about 30 ms 630+ ms > > In test2, we keep the number of the device the same as test1, reduce the > number of queues per device: > > Here are the test2 results: > test info: > - Host > - Intel(R) Xeon(R) Platinum 8260 CPU > - NVIDIA Mellanox ConnectX-5 > - VM > - 32 CPUs 128GB RAM VM > - 8 1-queue vhost-net device > - 16 1-queue vhost-user-blk device. > > time of loading non-iterable vmstate downtime > before about 90 ms about 250 ms > > after about 25 ms about 160 ms > > In test3, we keep the number of queues per device the same as test1, reduce > the number of devices: > > Here are the test3 results: > test info: > - Host > - Intel(R) Xeon(R) Platinum 8260 CPU > - NVIDIA Mellanox ConnectX-5 > - VM > - 32 CPUs 128GB RAM VM > - 1 16-queue vhost-net device > - 1 4-queue vhost-user-blk device. > > time of loading non-iterable vmstate downtime > before about 20 ms about 70 ms > after about 11 ms about 60 ms > > As we can see from the test results above, both the number of queues and > the number of devices have a great impact on the time of loading non-iterable > vmstate. The growth of the number of devices and queues will lead to more > mr commits, and the time consumption caused by the flatview reconstruction > will also increase. > > Signed-off-by: Chuang Xu <xuchuangxc...@bytedance.com>
Reviewed-by: Juan Quintela <quint...@redhat.com> And BTW, nice load times improvements.
