CPU and I/O Burst Cycles

Summary

This lecture delves into the concept of CPU scheduling, focusing on the alternating cycles of CPU and I/O bursts within process execution. It explains CPU burst as the active use of the CPU by a process and I/O burst as the waiting period for input/output operations to complete. The lecture uses a diagram to illustrate these bursts and emphasizes the importance of understanding these cycles for effective CPU scheduling, aiming to maximize CPU utilization and minimize idle time.

Takeaways

• 🕒 CPU Scheduling is about assigning time slots to different processes for their utilization of the CPU to avoid idleness.
• 🔄 Process execution alternates between two main states: CPU execution state and I/O waiting state.
• 💡 A CPU burst is the period when a process is actively using the CPU for execution.
• 🔄 An I/O burst is the period when a process is waiting for an I/O operation to complete, not utilizing the CPU.
• 🔁 The execution of a process typically follows a cycle of CPU burst followed by an I/O burst, repeating until termination.
• 📈 Maximizing CPU utilization is a key goal of effective CPU scheduling by managing these bursts.
• 🚫 The CPU should not remain idle while a process is waiting for I/O operations; it should be assigned to other processes.
• 🔚 The final CPU burst ends with a system request to terminate the process's execution.
• 📊 The script provides an example illustrating the alternating sequence of CPU and I/O bursts during process execution.
• 📝 Understanding the concepts of CPU burst and I/O burst is crucial for grasping the fundamentals of CPU scheduling.
• 👋 The lecture concludes with an emphasis on the importance of these concepts for anyone studying CPU scheduling.

Q & A

What is the primary purpose of CPU scheduling?

The primary purpose of CPU scheduling is to assign time to different processes for their utilization of the CPU, ensuring the CPU does not remain idle and maximizing its utilization.

What are the two main states a process can be in during its execution?

The two main states a process can be in during its execution are the CPU execution state and the input/output waiting state.

What is a CPU burst?

A CPU burst is the period of time when a process is actively using the CPU for its execution.

What is an I/O burst?

An I/O burst is the period of time when a process is waiting for an input/output operation to be completed, and is not using the CPU.

Why is it important for a process to alternate between CPU burst and I/O burst states?

It is important for a process to alternate between CPU burst and I/O burst states to ensure efficient use of the CPU, preventing it from being idle while waiting for I/O operations to complete.

What happens during the final CPU burst in a process's execution?

During the final CPU burst, the system issues a request to terminate the execution of the process, which leads to the process being terminated once the burst is completed.

Can you provide an example of a CPU burst from the script?

An example of a CPU burst from the script is when a process is performing operations such as load, store, add, and store, which require the use of the CPU.

Can you provide an example of an I/O burst from the script?

An example of an I/O burst from the script is when a process is waiting for an input/output operation to be completed, such as reading from a file.

What is the significance of understanding CPU and I/O bursts in CPU scheduling?

Understanding CPU and I/O bursts is significant in CPU scheduling as it helps in developing efficient scheduling algorithms that can balance CPU usage and I/O wait times, improving overall system performance.

How does the pattern of alternating CPU burst and I/O burst affect the performance of a system?

The pattern of alternating CPU burst and I/O burst affects system performance by determining how efficiently the CPU is used. Efficient alternation can lead to higher CPU utilization and reduced idle times, enhancing overall system throughput.

What is the role of process cancellation in the context of CPU and I/O bursts?

Process cancellation plays a role in CPU and I/O bursts by providing a mechanism to terminate a process's execution when necessary, allowing the CPU to be freed up for other processes, especially during the final CPU burst of a process's lifecycle.

Outlines

00:00

💻 CPU Scheduling and Burst Cycles Overview

This paragraph introduces the concept of CPU scheduling and the importance of utilizing the CPU efficiently to prevent idleness, especially during I/O operations. It explains the two primary states a process can be in: CPU execution state and I/O waiting state. The paragraph also defines CPU burst as the period a process actively uses the CPU and I/O burst as the time the process waits for I/O operations to complete. The explanation emphasizes the alternating pattern of these bursts in a process's execution, highlighting the goal of maximizing CPU utilization.

05:01

🔁 Example of CPU and I/O Burst Cycles in Process Execution

The second paragraph provides an illustrative example to demonstrate the cycle of CPU and I/O bursts in a process's execution. It describes a sequence of operations such as load, store, add, and file read/write, which require CPU usage (CPU burst) and periods of waiting for I/O operations to complete (I/O burst). The paragraph uses a diagram to visually represent this alternating sequence, showing how a process moves between needing CPU resources and waiting for I/O. It concludes with the final CPU burst, which includes a system request to terminate the process, marking the end of the CPU and I/O burst cycle for that process.

Keywords

💡CPU Scheduling

CPU Scheduling is the process of determining which process gets access to the CPU for execution. It is essential for efficient use of the CPU, ensuring that it is not idle while one process is waiting for I/O operations to complete. In the video, CPU scheduling is the overarching theme, with the script discussing how to manage CPU time to maximize its utilization.

💡CPU Burst

A CPU burst refers to a period when a process is actively using the CPU for execution. In the script, CPU bursts are depicted as phases where the process is engaged in operations such as load, store, and arithmetic computations, which require the CPU's processing power.

💡I/O Burst

An I/O burst is the time when a process is waiting for input/output operations to complete, and thus not actively using the CPU. The script illustrates I/O bursts as intervals where the process is idle, waiting for operations like reading from or writing to a file to finish.

💡Process Execution

Process execution refers to the running of a process, which involves alternating between CPU execution and waiting for I/O operations. The script describes process execution as a cycle of CPU bursts and I/O bursts, which is fundamental to understanding the process's behavior and the need for efficient CPU scheduling.

💡CPU Execution State

The CPU execution state is when a process is actively utilizing the CPU to perform tasks. The script mentions this state as a period where the process is in 'CPU burst,' making use of the CPU for its execution needs.

💡Input/Output Waiting State

The input/output waiting state is when a process is not using the CPU because it is waiting for I/O operations to be completed. The script describes this state as the 'I/O burst,' indicating the process is idle, waiting for I/O operations such as file reads or writes.

💡Process Termination

Process termination is the end of a process's execution, which can be initiated by the system or due to the process completing its task. The script explains that the final CPU burst often includes a system request to terminate the process's execution.

💡Process Cancellation

Process cancellation is a concept related to terminating a process's execution before it naturally completes. While the script does not delve deeply into this concept, it mentions process cancellation in the context of the final CPU burst leading to process termination.

💡Maximizing CPU Utilization

Maximizing CPU utilization is the goal of efficient CPU scheduling, aiming to keep the CPU busy and minimize idle time. The script emphasizes the importance of assigning CPU time to different processes to ensure the CPU is always in use, thus maximizing its utilization.

💡I/O Operations

I/O operations are tasks related to input and output, such as reading from or writing to a file. The script uses I/O operations as examples of activities that cause a process to enter an I/O burst, where it waits for these operations to complete before resuming CPU execution.

Highlights

Introduction to CPU scheduling and its importance for maximizing CPU utilization.

Definition of scheduling as the assignment of time for different processes to use the CPU.

Explanation of the need to avoid CPU idleness during IO operations by assigning CPU time to other processes.

Introduction to the concepts of CPU burst and IO burst as key terms in CPU scheduling.

Description of process execution as alternating between CPU execution and IO waiting states.

Clarification of CPU burst as the time a process is utilizing the CPU for execution.

Definition of IO burst as the time a process is waiting for IO operations to complete.

Illustration of how processes alternate between CPU bursts and IO bursts during execution.

Explanation of the final CPU burst ending with a system request to terminate process execution.

Discussion on process cancellation and termination in the context of CPU and IO bursts.

Presentation of a diagram depicting the alternating sequence of CPU and IO bursts.

Example of process execution cycle with operations like load, store, add, and read from file.

Demonstration of how a process uses CPU during operations and waits during IO bursts.

Continuation of the pattern of CPU bursts followed by IO bursts until process termination.

Final emphasis on the importance of understanding CPU burst and IO burst in CPU scheduling.

Conclusion and appreciation for the audience's attention to the lecture on CPU and IO bursts.

Transcripts

in the previous lecture we have started

studying about CPU scheduling and we

have seen a basic introduction to CPU

scheduling now moving ahead in this

lecture we'll be studying about CPU and

i/o burst cycles now when we studied

about CPU scheduling in the previous

lecture we understood what the

scheduling is in a very basic term so

what we actually mean by scheduling is

the time that we are assigning to

different processes for their

utilization of the CPU so we don't want

the CPU to remain idle when one process

that was in hold of the CPU is waiting

for some IO operations to complete so

during that waiting time we want the CPU

to be assigned to some other process so

that the CPU doesn't remain idle and

hence we can maximize the utilization of

our CPU so with regards to that these

are two important terms that we should

know and we should understand CPU burst

and IO burst so we will try to

understand what we mean by CPU burst and

i/o bus and we will also understand what

is the CPU and IO burst cycle so process

execution consists of a cycle of CPU

execution and i/o we so when we studied

about CPU scheduling we already saw that

a process can be in either of these two

states and what are those states CPU

execution state and input and output

waiting state so processes alternate

between these two states now what do we

mean by these two states of CPU

execution and input/output wait so when

a process has begun its execution it is

under the CPU execution state that means

it is making use of the CPU for its

execution so if it is in that state we

call it a CPU execution state and after

that the process may need to wait for an

input/output operation to be complete in

order to continue with its execution at

that time when it is waiting for an

input/output operation to be complete we

say that the process is in IO wait State

so these are the two states in which a

process can be in once it has begun its

execution so processes always alternate

between these two states of

execution order input/output we so when

we use the term CPU burst we should

understand that what we mean by CPU

burst is the time when the process is

under CPU execution so when the process

is under CPU execution we say that that

is a CPU burst and then when the process

is waiting for some IO operation to be

complete or when it is waiting then we

call it IO burst so in simple terms CPU

burst and IO burst are nothing but the

time in which the process is under CPU

execution and IO wait respectively so

that is what we mean by CPU and i/o bus

so when a process execution begins these

are the stages it goes through so

process execution begins with a cpu

burst that is followed by an i/o burst

which is followed by another CPU burst

then another i/o burst and so on so we

see that when a process begins its

execution it starts with a CPU burst

that means it is under CPU execution it

is using the CPU for its execution and

at some point of time it will need some

input/output operations to be done so at

that time it will wait for the input or

output operation to be complete and that

is what we call IO burst

so there is an IO burst over here and

after the IO burst is complete that

means after the wait for the

input/output operation is complete it

will again use the CPU for its execution

so hence we have a CPU burst again and

then again it may need to wait for some

input/output operations and hence we

have a input/output burst and so on this

pattern will continue it will alternate

between these two states of CPU burst

and IO burst and it will go on so these

are the stages data process goes through

in its execution it is alternating

between the two states of CPU burst and

i/o burst so remember the meanings of

Scipio bus and i/o bus again

CPU burst is when the process is being

executed in the CPU and IO burst is when

the CPU is waiting for I

for further execution that means when

the CPU is waiting for some input/output

operations to be complete then we call

it IO burst so that is CPU burst an IO

burst and processes they alternate

between these two states during the

course of its execution and eventually

the final CPU burst ends with a system

request to terminate execution so once

these pattern continues and at the end

what happens is that there will be a

final CPU burst that means a final

execution of the CPU in which there will

be a system request to terminate the

execution of a process so we have

already studied abroad process

cancellation and we have seen what do we

mean by process cancellation and how

process termination takes place now let

us look at a simple example to see and

understand the way CPU burst and i/o

burst occurs in a process execution

cycle so here is a small diagram in

which the alternating sequence of CPU

and i/o bursts are depicted here we

assume that a process has begun its

execution and these are some of the

operations that are performed during the

execution of a process so here we see

there are some operations like load

store add store and read from file so

these are the operations that has to be

performed in the CPU so the process

requires the processor or the CPU for

this to happen at this time the process

is using the CPU and that time is known

as CPU burst and after this operation is

complete the process is waiting for some

input output operation to be performed

so here it is waiting for input output

and at that time when it is waiting for

input/output it is not using the CPU and

at that time we call it is a IO burst or

input/output burst and again we see that

after the wait was complete Alfred I Oh

operation has been completed

there are some other operations like

store increment index or a right to file

so these are operations that again

requires the CPU or the processor so at

this time when the process is doing this

with the help of the CPU we call it a

CPU burst

and again similarly it comes down and

has to use some input/output operations

so it is waiting for the input/output

operation to be complete and there we

have our yoke blessed again and moving

forward again there are some operations

like Lord store ad store it from file

which is similar to this one so we

already saw that this is our kind of

operation that requires the CPU so this

is again a CPU burst and then it is

again waiting for some i/o operation to

be complete which is known as the i/o

burst and this pattern continues and

until when will it continue it will

continue till the processes terminated

so when the process is going to be

terminated there will be a final CPU

burst in which the system will request

for the termination of the process and

once that is completed this process will

be terminated and then the CPU and IO

burst cycle for that particular process

will be finished that is what we mean by

CPU burst and IO burst and here we have

seen an example of how it happens so as

we continue studying about CPU

scheduling these are two important

things that we should always keep in

mind and whenever we use this terms of

CPU burst or i/o burst you should always

remember what it means as we have

studied in this lecture so I hope this

lecture about CPU burst and i/o burst

and CPU and i/o bus cycles were clear to

you thank you for watching and see you

in the next one

[Applause]

you

[Music]