[the_why_of_y]

Processing CPU interrupts has overheads. Previously for storage devices you always get one CPU interrupt per I/O operation. If you have many SSDs with some ridiculous IOPS then you spend a lot of CPU handling all those interrupts.

This change means that when the I/O load is high there is no longer one CPU interrupt per I/O operation, instead multiple operations are processed at once, so the CPU has more time to run user space applications to actually do something with all that data.