diff --git a/Cargo.toml b/Cargo.toml
index 8e5c658..649e93e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,6 +32,7 @@ anyhow = "1.0.89"
 thiserror = "2.0"
 bitflags = "2.6"
 core_affinity = "0.8.1"
+parking_lot_core = "0.9.10"
 # derive_more = "1.0.0"
 
 [dev-dependencies]
diff --git a/src/job/mod.rs b/src/job/mod.rs
index 386ce78..6d09c1d 100644
--- a/src/job/mod.rs
+++ b/src/job/mod.rs
@@ -3,6 +3,9 @@ use std::{cell::UnsafeCell, marker::PhantomPinned, sync::atomic::AtomicBool};
 
 use crate::latch::Latch;
 
+pub mod spice;
+pub mod v2;
+
 pub trait Job<Args = ()> {
     unsafe fn execute(this: *const (), args: Args);
 }
@@ -35,23 +38,15 @@ impl<Args> JobRef<Args> {
     }
 }
 
-pub struct StackJob<F, L>
-where
-    L: Latch + Sync,
-{
+pub struct StackJob<F> {
     task: UnsafeCell<Option<F>>,
-    latch: L,
     _phantom: PhantomPinned,
 }
 
-impl<F, L> StackJob<F, L>
-where
-    L: Latch + Sync,
-{
-    pub fn new(task: F, latch: L) -> StackJob<F, L> {
+impl<F> StackJob<F> {
+    pub fn new(task: F) -> StackJob<F> {
         Self {
             task: UnsafeCell::new(Some(task)),
-            latch,
             _phantom: PhantomPinned,
         }
     }
@@ -77,16 +72,14 @@ where
     }
 }
 
-impl<Args, F, L> Job<Args> for StackJob<F, L>
+impl<Args, F> Job<Args> for StackJob<F>
 where
     F: FnOnce(Args),
-    L: Latch + Sync,
 {
     unsafe fn execute(this: *const (), args: Args) {
         let this = &*this.cast::<Self>();
         let func = (*this.task.get()).take().unwrap();
         func(args);
-        Latch::set_raw(&this.latch);
         // set internal latch here?
     }
 }
diff --git a/src/job/spice.rs b/src/job/spice.rs
new file mode 100644
index 0000000..9cb6cba
--- /dev/null
+++ b/src/job/spice.rs
@@ -0,0 +1 @@
+use std::{cell::UnsafeCell, sync::atomic::AtomicU8};
diff --git a/src/job/v2.rs b/src/job/v2.rs
new file mode 100644
index 0000000..b3c6adb
--- /dev/null
+++ b/src/job/v2.rs
@@ -0,0 +1,256 @@
+use core::{
+    cell::UnsafeCell,
+    mem::{self, ManuallyDrop, MaybeUninit},
+    sync::atomic::{AtomicU8, Ordering},
+};
+use std::thread::Thread;
+
+use parking_lot_core::SpinWait;
+
+use crate::util::SendPtr;
+
+#[allow(dead_code)]
+#[cfg_attr(target_pointer_width = "64", repr(align(16)))]
+#[cfg_attr(target_pointer_width = "32", repr(align(8)))]
+#[derive(Debug, Default, Clone, Copy)]
+struct Size2([usize; 2]);
+
+struct Value<T>(pub MaybeUninit<Box<MaybeUninit<T>>>);
+
+impl<T> Value<T> {
+    unsafe fn get(self, inline: bool) -> T {
+        if inline {
+            unsafe { mem::transmute_copy(&self.0) }
+        } else {
+            unsafe { (*self.0.assume_init()).assume_init() }
+        }
+    }
+}
+
+#[repr(u8)]
+pub enum JobState {
+    Empty,
+    Locked = 1,
+    Pending,
+    Finished,
+    Inline = 1 << (u8::BITS - 1),
+}
+
+pub struct Job<T = ()> {
+    state: AtomicU8,
+    this: SendPtr<()>,
+    harness: unsafe fn(*const (), *const Job<()>),
+    maybe_boxed_val: UnsafeCell<MaybeUninit<Value<T>>>,
+    waiting_thread: UnsafeCell<Option<Thread>>,
+}
+
+impl<T> Job<T> {
+    pub fn state(&self) -> u8 {
+        self.state.load(Ordering::Relaxed) & !(JobState::Inline as u8)
+    }
+    pub fn wait(&self) -> Option<T> {
+        let mut state = self.state.load(Ordering::Relaxed);
+        let mask = JobState::Inline as u8;
+
+        let mut spin = SpinWait::new();
+        loop {
+            match self.state.compare_exchange(
+                JobState::Pending as u8 | (state & mask),
+                JobState::Locked as u8 | (state & mask),
+                Ordering::Acquire,
+                Ordering::Relaxed,
+            ) {
+                Ok(x) => {
+                    state = x;
+                    unsafe {
+                        *self.waiting_thread.get() = Some(std::thread::current());
+                    }
+
+                    self.state
+                        .store(JobState::Pending as u8 | (state & mask), Ordering::Release);
+                    std::thread::park();
+                    spin.reset();
+                    break;
+                }
+                Err(x) => {
+                    if x & JobState::Finished as u8 != 0 {
+                        let val = unsafe {
+                            let value = (&*self.maybe_boxed_val.get()).assume_init_read();
+                            value.get(state & JobState::Inline as u8 != 0)
+                        };
+                        return Some(val);
+                    } else {
+                        spin.spin();
+                    }
+                }
+            }
+        }
+        return None;
+    }
+    /// call this when popping value from local queue
+    pub fn set_pending(&self) {
+        let state = self.state.load(Ordering::Relaxed);
+        let mask = JobState::Inline as u8;
+
+        let mut spin = SpinWait::new();
+        loop {
+            match self.state.compare_exchange(
+                JobState::Empty as u8 | (state & mask),
+                JobState::Pending as u8 | (state & mask),
+                Ordering::Acquire,
+                Ordering::Relaxed,
+            ) {
+                Ok(_) => {
+                    return;
+                }
+                Err(_) => {
+                    spin.spin();
+                }
+            }
+        }
+    }
+
+    pub fn execute(&self) {
+        // SAFETY: self is non-null
+        unsafe { (self.harness)(self.this.as_ptr().cast(), (self as *const Self).cast()) };
+    }
+
+    fn complete(&self, result: T) {
+        let mut state = self.state.load(Ordering::Relaxed);
+        let mask = JobState::Inline as u8;
+
+        let mut spin = SpinWait::new();
+        loop {
+            match self.state.compare_exchange(
+                JobState::Pending as u8 | (state & mask),
+                JobState::Locked as u8 | (state & mask),
+                Ordering::Acquire,
+                Ordering::Relaxed,
+            ) {
+                Ok(x) => {
+                    state = x;
+                    break;
+                }
+                Err(_) => {
+                    spin.spin();
+                }
+            }
+        }
+
+        unsafe {
+            let value = (&mut *self.maybe_boxed_val.get()).assume_init_mut();
+            // SAFETY: we know the box is allocated if state was `Pending`.
+            if state & JobState::Inline as u8 == 0 {
+                value.0 = MaybeUninit::new(Box::new(MaybeUninit::new(result)));
+            } else {
+                *mem::transmute::<_, &mut T>(&mut value.0) = result;
+            }
+        }
+
+        if let Some(thread) = unsafe { &mut *self.waiting_thread.get() }.take() {
+            thread.unpark();
+        }
+
+        self.state
+            .store(JobState::Finished as u8 | (state & mask), Ordering::Release);
+    }
+}
+
+impl Job {}
+
+pub struct HeapJob<F> {
+    f: F,
+}
+
+impl<F> HeapJob<F> {
+    pub fn new(f: F) -> Box<Self> {
+        Box::new(Self { f })
+    }
+    pub fn into_boxed_job<T>(self: Box<Self>) -> Box<Job<()>>
+    where
+        F: FnOnce() -> T + Send,
+        T: Send,
+    {
+        unsafe fn harness<F, T>(this: *const (), job: *const Job<()>)
+        where
+            F: FnOnce() -> T + Send,
+            T: Sized + Send,
+        {
+            let job = unsafe { &*job.cast::<Job<T>>() };
+
+            let this = unsafe { Box::from_raw(this.cast::<HeapJob<F>>().cast_mut()) };
+            let f = this.f;
+
+            job.complete(f());
+        }
+
+        let size = mem::size_of::<T>();
+        let align = mem::align_of::<T>();
+
+        let new_state = if size > mem::size_of::<Box<T>>() || align > mem::align_of::<Box<T>>() {
+            JobState::Empty as u8
+        } else {
+            JobState::Inline as u8
+        };
+
+        Box::new(Job {
+            state: AtomicU8::new(new_state),
+            this: SendPtr::new(Box::into_raw(self)).unwrap().cast(),
+            waiting_thread: UnsafeCell::new(None),
+            harness: harness::<F, T>,
+            maybe_boxed_val: UnsafeCell::new(MaybeUninit::uninit()),
+        })
+    }
+}
+
+pub struct StackJob<F> {
+    f: UnsafeCell<ManuallyDrop<F>>,
+}
+
+impl<F> StackJob<F> {
+    pub fn new(f: F) -> Self {
+        Self {
+            f: UnsafeCell::new(ManuallyDrop::new(f)),
+        }
+    }
+
+    pub unsafe fn unwrap(&self) -> F {
+        unsafe { ManuallyDrop::take(&mut *self.f.get()) }
+    }
+
+    pub fn as_boxed_job<T>(&self) -> Box<Job<()>>
+    where
+        F: FnOnce() -> T + Send,
+        T: Send,
+    {
+        unsafe fn harness<F, T>(this: *const (), job: *const Job<()>)
+        where
+            F: FnOnce() -> T + Send,
+            T: Sized + Send,
+        {
+            let job = unsafe { &*job.cast::<Job<T>>() };
+
+            let this = unsafe { &*this.cast::<StackJob<F>>() };
+            let f = unsafe { this.unwrap() };
+
+            job.complete(f());
+        }
+
+        let size = mem::size_of::<T>();
+        let align = mem::align_of::<T>();
+
+        let new_state = if size > mem::size_of::<Box<T>>() || align > mem::align_of::<Box<T>>() {
+            JobState::Empty as u8
+        } else {
+            JobState::Inline as u8
+        };
+
+        Box::new(Job {
+            state: AtomicU8::new(new_state),
+            this: SendPtr::new(self).unwrap().cast(),
+            waiting_thread: UnsafeCell::new(None),
+            harness: harness::<F, T>,
+            maybe_boxed_val: UnsafeCell::new(MaybeUninit::uninit()),
+        })
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 1b5c87d..0b953ec 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -28,6 +28,7 @@ use task::{HeapTask, StackTask, TaskRef};
 use tracing::debug;
 
 pub mod job;
+pub mod util;
 
 pub mod task {
     use std::{cell::UnsafeCell, marker::PhantomPinned, pin::Pin};
diff --git a/src/melange.rs b/src/melange.rs
index 40b1ce9..da69c0d 100644
--- a/src/melange.rs
+++ b/src/melange.rs
@@ -3,20 +3,19 @@ use std::{
     collections::VecDeque,
     marker::PhantomPinned,
     ops::{Deref, DerefMut},
-    pin::pin,
     ptr::{self, NonNull},
     sync::{
         atomic::{AtomicBool, Ordering},
         Arc, Weak,
     },
     thread,
-    time::{Duration, Instant},
+    time::Duration,
 };
 
 use crossbeam::utils::CachePadded;
 use parking_lot::{Condvar, Mutex};
 
-use crate::{latch::*, task::*, ThreadControl, ThreadStatus};
+use crate::{latch::*, ThreadControl};
 mod job {
     use std::{
         cell::{Cell, UnsafeCell},
@@ -304,7 +303,8 @@ mod job {
 }
 
 //use job::{Future, Job, JobQueue, JobStack};
-use crate::job::{Job, JobRef, StackJob};
+use crate::job::v2::{Job, JobState, StackJob};
+// use crate::job::{Job, JobRef, StackJob};
 
 struct ThreadState {
     control: ThreadControl,
@@ -312,11 +312,10 @@ struct ThreadState {
 
 struct Heartbeat {
     is_set: Weak<AtomicBool>,
-    last_time: Cell<Instant>,
 }
 
 pub struct SharedContext {
-    shared_tasks: Vec<Option<JobRef>>,
+    shared_tasks: Vec<Option<NonNull<Job>>>,
     heartbeats: Vec<Option<Heartbeat>>,
     rng: crate::rng::XorShift64Star,
 }
@@ -337,7 +336,6 @@ impl SharedContext {
         let is_set = Arc::new(AtomicBool::new(true));
         let heartbeat = Heartbeat {
             is_set: Arc::downgrade(&is_set),
-            last_time: Cell::new(Instant::now()),
         };
 
         let index = match self.heartbeats.iter().position(|a| a.is_none()) {
@@ -355,7 +353,7 @@ impl SharedContext {
         (is_set, index)
     }
 
-    fn pop_first_task(&mut self) -> Option<JobRef> {
+    fn pop_first_task(&mut self) -> Option<NonNull<Job>> {
         self.shared_tasks
             .iter_mut()
             .filter_map(|task| task.take())
@@ -376,7 +374,7 @@ std::thread_local! {
 pub struct WorkerThread {
     context: Arc<Context>,
     index: usize,
-    queue: VecDeque<JobRef>,
+    queue: VecDeque<NonNull<Job>>,
     heartbeat: Arc<AtomicBool>,
     join_count: u8,
     sleep_count: usize,
@@ -504,8 +502,10 @@ impl WorkerThread {
         }
     }
 
-    fn execute_job(&mut self, job: JobRef) {
-        unsafe { core::mem::transmute::<JobRef, JobRef<&mut WorkerThread>>(job).execute(self) };
+    fn execute_job(&mut self, job: NonNull<Job>) {
+        unsafe {
+            job.as_ref().execute();
+        }
     }
 
     #[cold]
@@ -569,18 +569,19 @@ impl WorkerThread {
         RB: Send,
     {
         let mut ra = None;
+        let latch = AtomicLatch::new();
         let a = |scope: &mut WorkerThread| {
             if scope.heartbeat.load(Ordering::Relaxed) {
                 scope.heartbeat_cold();
             }
 
             ra = Some(a(scope));
+            unsafe {
+                Latch::set_raw(&latch);
+            }
         };
 
-        let latch = AtomicLatch::new();
-        let ctx = self.context.clone();
-        let idx = self.index;
-        let stack = StackJob::new(a, latch);
+        let stack = StackJob::new(a);
         let task: JobRef =
             unsafe { core::mem::transmute::<JobRef<_>, JobRef>(stack.as_task_ref()) };
 
@@ -631,27 +632,33 @@ impl WorkerThread {
 
 impl Context {
     fn heartbeat(self: Arc<Self>, interaval: Duration) {
+        let mut n = 0;
         loop {
             if self.heartbeat_control.should_terminate.probe() {
                 break;
             }
             let sleep_for = {
                 let guard = self.shared.lock();
-                let now = Instant::now();
 
                 let num_heartbeats = guard
                     .heartbeats
                     .iter()
                     .filter_map(Option::as_ref)
-                    .filter_map(|h| h.is_set.upgrade().map(|is_set| (is_set, &h.last_time)))
-                    .inspect(|(is_set, last_time)| {
-                        if now.duration_since(last_time.get()) >= interaval {
+                    .filter_map(|h| h.is_set.upgrade().map(|is_set| is_set))
+                    .enumerate()
+                    .inspect(|(i, is_set)| {
+                        if *i == n {
                             is_set.store(true, Ordering::Relaxed);
-                            last_time.set(now);
                         }
                     })
                     .count();
 
+                if n >= num_heartbeats {
+                    n = 0;
+                } else {
+                    n += 1;
+                }
+
                 interaval.checked_div(num_heartbeats as u32)
             };
 
@@ -660,6 +667,41 @@ impl Context {
             }
         }
     }
+
+    fn heartbeat2(self: Arc<Self>, interval: Duration) {
+        let mut i = 0;
+        loop {
+            if self.heartbeat_control.should_terminate.probe() {
+                break;
+            }
+            let sleep_for = {
+                let guard = self.shared.lock();
+
+                let mut num = 0;
+                for is_set in guard
+                    .heartbeats
+                    .iter()
+                    .filter_map(Option::as_ref)
+                    .filter_map(|h| h.is_set.upgrade())
+                {
+                    if num == i {
+                        is_set.store(true, Ordering::Relaxed);
+                    }
+                    num += 1;
+                }
+
+                if num >= i {
+                    i = 0;
+                }
+
+                interval.checked_div(num)
+            };
+
+            if let Some(duration) = sleep_for {
+                thread::sleep(duration);
+            }
+        }
+    }
 }
 
 impl Drop for Context {
@@ -714,7 +756,7 @@ impl ThreadPool {
 
         let ctx = this.context.clone();
         std::thread::spawn(|| {
-            ctx.heartbeat(Duration::from_micros(100));
+            ctx.heartbeat2(Duration::from_micros(100));
         });
 
         this
diff --git a/src/util.rs b/src/util.rs
new file mode 100644
index 0000000..f903d8f
--- /dev/null
+++ b/src/util.rs
@@ -0,0 +1,67 @@
+use core::{
+    cell::Cell,
+    ops::{Deref, DerefMut},
+    ptr::NonNull,
+};
+
+#[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+#[repr(transparent)]
+pub struct SendPtr<T>(NonNull<T>);
+
+impl<T> SendPtr<T> {
+    pub fn as_ptr(&self) -> *mut T {
+        self.0.as_ptr()
+    }
+    pub unsafe fn new_unchecked(t: *const T) -> Self {
+        unsafe { Self(NonNull::new_unchecked(t.cast_mut())) }
+    }
+    pub fn new(t: *const T) -> Option<Self> {
+        NonNull::new(t.cast_mut()).map(Self)
+    }
+    pub fn cast<U>(self) -> SendPtr<U> {
+        SendPtr(self.0.cast::<U>())
+    }
+}
+
+impl<T> Deref for SendPtr<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        unsafe { &*self.0.as_ptr() }
+    }
+}
+
+impl<T> DerefMut for SendPtr<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { &mut *self.0.as_ptr() }
+    }
+}
+
+pub struct XorShift64Star {
+    state: Cell<u64>,
+}
+
+impl XorShift64Star {
+    /// Initializes the prng with a seed. Provided seed must be nonzero.
+    pub fn new(seed: u64) -> Self {
+        XorShift64Star {
+            state: Cell::new(seed),
+        }
+    }
+
+    /// Returns a pseudorandom number.
+    pub fn next(&self) -> u64 {
+        let mut x = self.state.get();
+        debug_assert_ne!(x, 0);
+        x ^= x >> 12;
+        x ^= x << 25;
+        x ^= x >> 27;
+        self.state.set(x);
+        x.wrapping_mul(0x2545_f491_4f6c_dd1d)
+    }
+
+    /// Return a pseudorandom number from `0..n`.
+    pub fn next_usize(&self, n: usize) -> usize {
+        (self.next() % n as u64) as usize
+    }
+}