An important feature within the Linux I/O stack is a part of the kernel block layer called the I/O scheduler. The issue being addressed here is basically this: I/O requests are being more or less continually issued by the kernel (due to apps wanting to perform various file data/code reads and writes); this results in a continuous stream of I/O requests being ultimately received and processed by the block driver(s). The kernel folks know that one of the primary reasons that I/O sucks out performance is that the physical seek of a typical SCSI disk is really slow (compared to silicon speeds; yes, of course, SSDs (solid state devices) are making this a lot more palatable nowadays).
So, if we could use some intelligence to sort ...
