GPU jump during rendering, is this normal?

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Recently I changed the GPU from 1080ti to 4080s, but keep the CPU as the old 8700K. Now there is a strange thing happened during rendering: the GPU usage always continue jump while the CPU usage is in a line and not overloaded, no matter the PC power option is in balance or in high performance. I can remember the usage was always in 99%-100% when using 1080ti.

Is this GPU jump normal? What's the possible problem of my settings?

Above is under SubD 3, below is SubD 4, it brings more deep jump, is that something related to SubD?