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d25675ff44
Provide a knob in scx_rustland_core to automatically turn the scheduler into a simple FIFO when the system is underutilized. This choice is based on the assumption that, in the case of system underutilization (less tasks running than the amount of available CPUs), the best scheduling policy is FIFO. With this option enabled the scheduler starts in FIFO mode. If most of the CPUs are busy (nr_running >= num_cpus - 1), the scheduler immediately exits from FIFO mode and starts to apply the logic implemented by the user-space component. Then the scheduler can switch back to FIFO if there are no tasks waiting to be scheduled (evaluated using a moving average). This option can be enabled/disabled by the user-space scheduler using the fifo_sched parameter in BpfScheduler: if set, the BPF component will periodically check for system utilization and switch back and forth to FIFO mode based on that. This allows to improve performance of workloads that are using a small amount of the available CPUs in the system, while still maintaining the same good level of performance for interactive tasks when the system is over commissioned. In certain video games, such as Baldur's Gate 3 or Counter-Strike 2, running in "normal" system conditions, we can experience a boost in fps of approximately 4-8% with this change applied. Signed-off-by: Andrea Righi <andrea.righi@canonical.com> |
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scx_rlfifo
This is a single user-defined scheduler used within sched_ext, which is a Linux kernel feature which enables implementing kernel thread schedulers in BPF and dynamically loading them. Read more about sched_ext.
Overview
scx_rlfifo is a simple FIFO scheduler runs in user-space, based on the scx_rustland_core framework.
Typical Use Case
This scheduler is provided as a simple template that can be used as a baseline to test more complex scheduling policies.
Production Ready?
Definitely not. Using this scheduler in a production environment is not recommended, unless there are specific requirements that necessitate a basic FIFO scheduling approach. Even then, it's still recommended to use the kernel's SCHED_FIFO real-time class.