When a process waits for a block device data request to complete, it incurs I/O wait time, and all idle time becomes wait time.
当一个过程等待一个块设备数据请求完成时,它会增加 I/O 等待时间,而所有空闲都会变成等待时间。
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The two biggest drawbacks to KVM are that it requires newer virtualization-capable processors and a user-space QEMU process to provide I/O virtualization.
This can cut the time required to process queries by as much as 20 percent because more data can be kept in memory, reducing the number of I/O operations to slower mechanical disk drives.