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ke: add turnstile and mutex

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Loïc Grégoire
2026-06-12 15:53:10 -04:00
parent 042a5d87d2
commit 68e0f7f8f7
7 changed files with 596 additions and 43 deletions
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src/kern/sched.zig
+34 -33
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@@ -207,8 +207,7 @@ pub fn clock(_: ?*anyopaque) void {
cpu.insidx = (cpu.insidx + 1) % runqueues_n;
}
if (curtd.priority_class() == .Batch) {
// Update interactivity metrics.
if (curtd.base_priority_class() == .Batch) {
curtd.run_time += config.sched_timeslice;
clamp_time(curtd);
@@ -265,7 +264,7 @@ pub fn unblock(td: *ke.Thread) void {
td.sleep_time = (ke.time.read_time() - td.sleep_start) / std.time.ns_per_ms;
if (td.sleep_time >= config.sched_timeslice and td.priority_class() == .Batch) {
if (td.sleep_time >= config.sched_timeslice and td.base_priority_class() == .Batch) {
// If we have slept for more than a tick, update interactivity.
clamp_time(td);
recompute_priority(td);
@@ -554,7 +553,7 @@ fn remove_from_queue(cpu: *PerCpu, td: *ke.Thread) void {
std.debug.assert(cpu.queues_lock.is_locked());
// Decrease load.
cpu.load.fetchSub(1, .monotonic);
_ = cpu.load.fetchSub(1, .monotonic);
// Remove the thread from its queue.
td.runq_link.remove();
@@ -627,7 +626,7 @@ fn interactive_score(td: *ke.Thread) usize {
return score;
}
// Recompute the priority for a thread.
// Recompute the base priority for a thread from interactivity and nice.
fn recompute_priority(td: *ke.Thread) void {
// Priority is computed only for time-shared (batch) thread based on
@@ -637,41 +636,43 @@ fn recompute_priority(td: *ke.Thread) void {
// priority is calculated based on recent CPU usage and nice.
const score = interactive_score(td);
if (score < interactivity_threshold) {
const base: u8 = if (score < interactivity_threshold)
// Choose a priority based on score, the lower the score,
// the higher the priority it will be.
// This is a simple formula I came up with that is probably good enough.
td.priority = @intCast(ke.Thread.Priority.low_interactive + ((interactivity_threshold - score) / 2));
return;
}
@intCast(ke.Thread.Priority.low_interactive + ((interactivity_threshold - score) / 2))
else blk: {
// Thread is not interactive, compute priority from recent CPU usage.
// cpu_pri_off is the fraction of the history window spent running,
// scaled to [0, batch_range). A thread that spent all its time running
// gets cpu_pri_off = batch_range - 1 (lowest priority).
// A thread that barely ran gets cpu_pri_off = 0 (highest batch priority).
// This is a pretty straightforward formula, which /should/ be good enough.
const cpu_range = ke.Thread.Priority.batch_range;
const window = if (td.run_time + td.sleep_time == 0) @as(u64, 1) else td.run_time + td.sleep_time;
const cpu_pri_off: u8 = @intCast((td.run_time * (cpu_range - 1)) / window);
// Thread is not interactive, compute priority from recent CPU usage.
// cpu_pri_off is the fraction of the history window spent running,
// scaled to [0, batch_range). A thread that spent all its time running
// gets cpu_pri_off = batch_range - 1 (lowest priority).
// A thread that barely ran gets cpu_pri_off = 0 (highest batch priority).
// This is a pretty straightforward formula, which /should/ be good enough.
const cpu_range = ke.Thread.Priority.batch_range;
const window = if (td.run_time + td.sleep_time == 0) @as(u64, 1) else td.run_time + td.sleep_time;
const cpu_pri_off: u8 = @intCast((td.run_time * (cpu_range - 1)) / window);
// nice offset: negative nice increases priority value, positive decreases it.
// Clamped to half the range to avoid pushing priority out of bounds before clamping.
const nice_off = std.math.clamp(
-@as(i32, td.nice),
-@as(i32, cpu_range / 2),
@as(i32, cpu_range / 2),
);
// nice offset: negative nice increases priority value, positive decreases it.
// Clamped to half the range to avoid pushing priority out of bounds before clamping.
const nice_off = std.math.clamp(
-@as(i32, td.nice),
-@as(i32, cpu_range / 2),
@as(i32, cpu_range / 2),
);
const raw = @as(i32, ke.Thread.Priority.low_batch) +
@as(i32, cpu_pri_off) +
nice_off;
const raw = @as(i32, ke.Thread.Priority.low_batch) +
@as(i32, cpu_pri_off) +
nice_off;
break :blk @intCast(std.math.clamp(
raw,
ke.Thread.Priority.low_batch,
ke.Thread.Priority.high_batch,
));
};
td.priority = @intCast(std.math.clamp(
raw,
ke.Thread.Priority.low_batch,
ke.Thread.Priority.high_batch,
));
td.base_priority = base;
td.priority = td.effective_priority();
}
// Return whether or not a thread with given priority and interactivity should get preempted by `td`.