Why does host kvcache need to be larger than device cache

[yuukidach]

In host cache implementaion, there is an assertion

assert (
    self.size > device_pool.size
), "The host memory should be larger than the device memory with the current protocol"

I want to know why this assertion is necessary. Even if the host cache is smaller than the device cache, it should still work properly

[hnyls2002]

@xiezhq-hermann Can you explain this?

[stmatengss]

In extreme cases, such as when there's no storage backend and the device cache is full, offloading to hicache will cause an OOM error. To better handle this case, a more sophisticated method should be used, eliminating the need to ensure the host KV cache is larger than the device cache.