There are many different ways that i/o scheduling can be done. Linux I/O Schedulers There are many different ways that i/o scheduling can be done.

How IO works on linux Programmed I/O: The processor issues an I/O command, on behalf of a process, to an I/O module; that process then busy waits for the operation to be completed before proceeding. • a process. There are then two possibilities. If the I/O instruction from the Interrupt-driven I/O: The processor issues an I/O command on behalf of process is nonblocking, then the processor continues to execute instructions from the process that issued the I/O command. If the I/O instruction is blocking,then the next instruction that the processor executes is from another process. contiued

How IO WORKS ON LINUx Direct memory access (DMA): A DMA module controls the exchange of data between main memory and an I/O module. The processor sends a request for the transfer of a block of data to the DMA module and is interrupted only after the entire block has been transferred.

IO controlled by it’s own processor More and more laptops and computers are coming with IO controller that have their own cpu on it that can speed IO up and not have noticeable blocks that an end user would notice

Below is a graphic which explains it as it relates to us

Io Schedulers:Design and problems Most Computers harddrive, until recently, were magnetic rotational harddrives so to prevent wear and tear on expensive hardrives, and if the scheduler was written correctly limit user delay.Thankfully now almost all computers have ssds Originally only three or 4 IO scheduling algorithms existed each with their own use case scenarios, now there are many different Io Scheduling algorithms and schemes to eek out as much power as needed,

Rotational Delay explained more On a movable-head system, the time it takes to position the head at the track is known as seek time . In either case, once the track is selected, the disk controller waits until the appropriate sector rotates to line up with the head. The time it takes for the beginning of the sector to reach the head is known as rotational delay , or rotational latency. The sum of the seek time, if any, and the rotational delay equals the access time , which is the time it takes to get into position to read or write. Once the head is in position, the read or write operation is then performed as the sector moves under the head; this is the data transfer portion of the operation; the time required for the transfer is the transfer time. –Operating Systems internal and design principles

Models Being familiar with the linux kernel on android I decided to model noop(fcfs), RoundRobin, Shortest Job First,UniProgramming With the exception of fcfs all of these sort and try to maximize throughput of io by guessing where the disk head is or how much processing the caller process is using.

What Schedulers are out there Lots. The main ones that are standard to the linux kernel are Deadling, anticipatory, no/op(fcfs),shortest job first, and Round Robin. Each one has their own use case whjere the performace gained is appropriate for whatever the computers doing.

All in all ioschedulers are important All done