If you’re running a Fedora Workstation, you may have noticed that there are several I/O schedulers to choose from. The I/O scheduler is responsible for determining the order in which read and write requests are processed by the storage subsystem of your computer. Choosing the right scheduler can have a significant impact on system performance and responsiveness.

The default I/O scheduler for Fedora Workstation is mq-deadline, which is optimized for solid-state drives (SSDs) and provides a good balance between latency and throughput. However, if you have heavy I/O workloads and want to prioritize low latency and responsiveness over throughput, you may want to switch to the bfq scheduler.

To check the currently active scheduler for your block devices, run the following command in a terminal:

cat /sys/block/sda/queue/scheduler

Replace sda with the name of the block device, you want to check. The output will show the available I/O schedulers for the device, with the currently active scheduler in square brackets.

Output from the above cat command could be:

none [mq-deadline] kyber bfq

this means the active scheduler is mq-deadline, kyber and bfq are available

To change the I/O scheduler for your block devices, run the following command in a terminal:

sudo sh -c "echo <scheduler-name> > /sys/block/<device>/queue/scheduler"

Replace <scheduler-name> with the name of the scheduler you want to use (mq-deadline, kyber, or bfq), and <device> with the name of the block device you want to set the scheduler for (e.g., sda). Make sure to run the command with elevated privileges using sudo.

After changing the scheduler, you may want to test your system to see if the new scheduler provides better performance or responsiveness for your workload.

In summary, choosing the right I/O scheduler can have a significant impact on system performance and responsiveness. If you have heavy I/O workloads, consider switching to the bfq scheduler for improved latency and responsiveness. However, the default mq-deadline scheduler provides a good balance between latency and throughput and is a good choice for most users.

Appendum:

The best I/O scheduler for an SSD depends on your specific needs and workload. In general, mq-deadline is a good all-around choice, while kyber and bfq can be better for specific tasks.

• mq-deadline is a simple, straightforward scheduler that is good for general workloads. It provides good latency and throughput, and it is easy to configure.
• kyber is a more advanced scheduler that can provide better performance for some workloads. It is especially good for workloads with a lot of small, random I/O.
• bfq is another advanced scheduler that can provide better performance for some workloads. It is especially good for workloads with a lot of mixed I/O.

If you are not sure which scheduler to use, mq-deadline is a good place to start. If you are experiencing performance problems, you can try kyber or bfq to see if they provide better performance for your specific workload.

Here is a table that summarizes the pros and cons of each scheduler:

In Short

I/O schedulers are a crucial component of the Linux kernel that help manage and prioritize input/output (I/O) requests from various processes and applications. There are several different I/O schedulers available on Linux systems, including BFQ, Kyber, and MQ-Deadline.

BFQ (Budget Fair Queuing) is an I/O scheduler that is designed to provide low latency and fairness to I/O requests. It uses a complex algorithm that takes into account the size and urgency of I/O requests to improve system responsiveness. BFQ is a good all-around scheduler and is particularly well-suited for solid-state drives (SSDs).

Kyber is a newer I/O scheduler that was introduced in Linux kernel version 4.12. It is designed to improve I/O performance on SSDs by using a simple and predictable algorithm that reduces latency and improves throughput. Kyber is particularly effective for scenarios with heavy I/O loads or large amounts of small I/O requests.

MQ-Deadline is the default I/O scheduler in many Linux distributions, including Fedora. It uses a multiple-queue approach to handle I/O requests and can handle a large number of requests and prioritize them based on their deadline to improve system responsiveness.

Overall, the choice of I/O scheduler will depend on your specific hardware configuration, workload, and usage patterns. While BFQ is a good all-around scheduler, Kyber may be a better choice for SSDs and heavy I/O loads, and MQ-Deadline may be a good default choice for many users. It’s always a good idea to experiment with different schedulers and monitor their performance to find the best fit for your system.