Replace the BPF_MAP_TYPE_QUEUE with a BPF_MAP_TYPE_USER_RINGBUF to store
the tasks dispatched from the user-space scheduler to the BPF component.
This eliminates the need of the bpf() syscalls, significantly reducing
the overhead of the user-space->kernel communication and delivering a
notable performance boost in the overall system throughput.
Based on experimental results, this change allows to reduces the scheduling
overhead by approximately 30-35% when the system is overcommitted.
This improvement has the potential to make user-space schedulers based
on scx_rustland_core viable options for real production systems.
Link: https://github.com/libbpf/libbpf-rs/pull/776
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Do not encode dispatch flags in the cpu field, but simply use a separate
"flags" field.
This makes the code much simpler and it increases the size of
dispatched_task_ctx from 24 to 32, that is probably better in terms of
cacheline allocation / performance.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Introduce the new dispatch flag RL_PREEMPT_CPU that can be used to
dispatch tasks that can preempt others.
Tasks with this flag set will be dispatched by the BPF part using
SCX_ENQ_PREEMPT, so they can potentially preempt any other task running
on the target CPU.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Reserve some bits of the `cpu` attribute of a task to store special
dispatch flags.
Initially, let's introduce just RL_CPU_ANY to replace the special value
NO_CPU, indicating that the task can be dispatched on any CPU,
specifically the first CPU that becomes available.
This allows to keep the CPU value assigned by the builtin idle selection
logic, that can potentially be used later for further optimizations.
Moreover, having the possibility to specify dispatch flags gives more
flexibility and it allows to map new scheduling features to such flags.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
scx_rustland_core needs to ship both a binary part and a source code
part, which will be used to build schedulers based on it.
To effectively publish the scx_rustland_core crate on crates.io we need
to properly separate the source code assets from the crate's main source
code.
To achieve this, move the assets into a separate directory and declare
them inside a [lib] section in Cargo.toml.
This allows to publish the crate on crates.io, providing also a clear
separation between source code and assets.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
