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core::rt: Add some notes about optimizations

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Brian Anderson 2013-05-29 21:03:21 -07:00
parent f4ed554ddb
commit ca2eebd5dd
1 changed files with 14 additions and 0 deletions
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14
src/libstd/rt/sched.rs
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@ -29,6 +29,9 @@ use rt::rtio::{IoFactoryObject, RemoteCallback};
/// on a single thread. When the scheduler is running it is owned by
/// thread local storage and the running task is owned by the
/// scheduler.
///
/// XXX: This creates too many callbacks to run_sched_once, resulting
/// in too much allocation and too many events.
pub struct Scheduler {
/// A queue of available work. Under a work-stealing policy there
/// is one per Scheduler.
@ -143,6 +146,10 @@ pub impl Scheduler {
fn run_sched_once() {
// First, check the message queue for instructions.
// XXX: perf. Check for messages without atomics.
// It's ok if we miss messages occasionally, as long as
// we sync and check again before sleeping.
let sched = Local::take::<Scheduler>();
if sched.interpret_message_queue() {
// We performed a scheduling action. There may be other work
@ -153,6 +160,7 @@ pub impl Scheduler {
return;
}
// Now, look in the work queue for tasks to run
let sched = Local::take::<Scheduler>();
if sched.resume_task_from_queue() {
// We performed a scheduling action. There may be other work
@ -198,6 +206,12 @@ pub impl Scheduler {
self.event_loop.callback(Scheduler::run_sched_once);
// We've made work available. Notify a sleeping scheduler.
// XXX: perf. Check for a sleeper without synchronizing memory.
// It's not critical that we always find it.
// XXX: perf. If there's a sleeper then we might as well just send
// it the task directly instead of pushing it to the
// queue. That is essentially the intent here and it is less
// work.
match self.sleeper_list.pop() {
Some(handle) => {
let mut handle = handle;