spaceReserver HIGH_WATERMARK_RATIO'Default value should not be 1.0
We had better set the default value of
as 0.95 rather than 1.0 for each store_level
Because high watermark ratio is hard to be 1.0, when a new block want to enter the worker’s storage, if the worker’s space can not accept this block, the worker will evict some blocks to free space and let the new block getting in, then the worker’s space is still not full, so it still cannot reach the high watermark 1.0. So the 1.0 is not a better default value, maybe 0.95 is suitable.