PACKING REPLICATED WRITES (Utilizing CPU Time while waiting on replicated writes)
- Choosing an idle core for a new task
- New task creation when all cores are busy (Slow path for user thread creation)
- Single Global Queue vs Per-Core Queues needs an experiment.
- Task migration to balance load? (may not be needed if tasks are sufficiently short-lived)
LOGICAL CONCURRENCY VS DESIRED PARALLELISM (CORE COUNT)
- When should we ask the kernel for more cores, and when should we return cores to the kernel?
TIMING GUARANTEES UNDER COOPERATIVE THREADING
- Can we have any kind of timing guarantees without preemption?
BENEFITS / SELLING POINTS / CONTRIBUTIONS
- How much of knowledge of cores should bubble up to the application?
- What kind of guidance / hints can application offer to Arachne? e.g. priorities.
KERNEL API
CORE NEGOTIATION PROTOCOL
- What is said about cores?
- What is the mechanism for the communication? (e.g., shared memory, system call, etc.)
HANDLING BLOCKING SYSCALLS IN KERNEL (may be able to ignore for a while)
- Should Arachne know about the blocked user thread?
- What to do when syscall finishes? Don't preempt; shove the unblocked user thread into a queue
Mostly Solved Issues
MINIMUM TIME TO SCHEDULE A USER THREAD ONTO ANOTHER CORE
What is the correct architecture for the fast path, and what is the lowest possible time to schedule to another core?
DEFINITION OF CORE AWARE
- Knowledge of the number of nature of physical cores must move up the stack from the kernel into user-level libraries and possibly into applications