diff --git a/common/src/slowjob.rs b/common/src/slowjob.rs
index d88dadee9f..ff41d8a0ec 100644
--- a/common/src/slowjob.rs
+++ b/common/src/slowjob.rs
@@ -5,16 +5,33 @@ use std::sync::atomic::{Ordering, AtomicU64};
 use core::any::Any;
 use crossbeam_channel::{Receiver, Sender};
 
+type LimitFn = dyn Fn(u64) -> u64;
+
+/// a slow job is a CPU heavy task, that is not I/O blocking.
+/// It usually takes longer than a tick to compute, so it's outsourced
+/// Internally the rayon threadpool is used to calculate t
+pub struct SlowJobGroup<D> {
+    name: String,
+    next_id: Arc<AtomicU64>,
+    queue: Arc<RwLock<HashMap<u64, Queue>>>,
+    local_running_jobs: Arc<AtomicU64>,
+    global_running_jobs: Arc<AtomicU64>,
+    receiver: Arc<Receiver<(String, D)>>,
+    sender: Arc<Sender<(String, D)>>,
+}
+
 /// a slow job is a CPU heavy task, that is not I/O blocking.
 /// It usually takes longer than a tick to compute, so it's outsourced
 /// Internally the rayon threadpool is used to calculate t
 pub struct SlowJobPool {
     next_id: AtomicU64,
+    groups: RwLock<HashMap<String, Arc<SlowJobGroup<Box<dyn Any>>>>>,
     queue: RwLock<HashMap<String, HashMap<u64, Queue>>>,
     finished: RwLock<HashMap<String, Vec<Box<dyn Any>>>>,
     running_jobs: RwLock<HashMap<String, Arc<AtomicU64>>>,
     receiver: Receiver<(String, Box<dyn Any>)>,
     sender: Sender<(String, Box<dyn Any>)>,
+    global_limit: Box<LimitFn>,
 }
 
 pub struct SlowJob {
@@ -27,44 +44,28 @@ struct Queue {
     running_cnt: Arc<AtomicU64>,
 }
 
-
-impl SlowJobPool {
-    pub fn new() -> Self {
-        let (sender,receiver) = crossbeam_channel::unbounded();
-        Self {
-            next_id: AtomicU64::new(0),
-            queue: RwLock::new(HashMap::new()),
-            finished: RwLock::new(HashMap::new()),
-            receiver,
-            sender
-        }
-    }
-
+impl<D> SlowJobGroup<D> where
+    D: Any + Send + 'static
+{
     /// spawn a new slow job
-    pub fn spawn<F, D>(&self, name: &str, f: F) -> SlowJob where
-        F: FnOnce() -> D + Send + 'static,
-        D: Any + 'static,
+    pub fn spawn<F>(&self, name: &str, f: F) -> SlowJob where
+        F: FnOnce() -> D + 'static,
     {
         let id = self.next_id.fetch_add(1, Ordering::Relaxed);
-        let running_cnt = {
-            let mut lock = self.running_jobs.write().unwrap();
-            lock.entry(name.to_string()).or_default().clone()
-        };
-        let running_cnt_clone = Arc::clone(&running_cnt);
+        let local_running_jobs_clone = Arc::clone(&self.local_running_jobs);
+        let global_running_jobs_clone = Arc::clone(&self.global_running_jobs);
         let sender = self.sender.clone();
         let name_clone = name.to_string();
         let queue = Queue {
             task: Box::new(move || {
                 let result = f();
-                let _ = sender.send((name_clone, Box::new(result)));
-                running_cnt_clone.fetch_sub(1, Ordering::Relaxed);
+                let _ = sender.send((name_clone, result));
+                local_running_jobs_clone.fetch_sub(1, Ordering::Relaxed);
+                global_running_jobs_clone.fetch_sub(1, Ordering::Relaxed);
             }),
-            running_cnt,
+            running_cnt: Arc::clone(&self.local_running_jobs),
         };
-        {
-            let mut lock = self.queue.write().unwrap();
-            lock.entry(name.to_string()).or_default().insert(id, queue);
-        }
+        self.queue.write().unwrap().insert(id, queue);
         SlowJob {
             name: name.to_string(),
             id,
@@ -72,19 +73,41 @@ impl SlowJobPool {
     }
 
     pub fn cancel(&self, job: SlowJob) {
-        let mut lock = self.queue.write().unwrap();
-        if let Some(map) = lock.get_mut(&job.name) {
-            map.remove(&job.id);
-        }
+        self.queue.write().unwrap().remove(&job.id);
     }
 
     /// collect all slow jobs finished
-    pub fn collect(&self, name: &str) -> Vec<Box<dyn Any>> {
-        let mut lock = self.finished.write().unwrap();
+    pub fn collect(&self, name: &str) -> Vec<D> {
+        let mut result = vec!();
         for (name, data) in self.receiver.try_iter() {
-            lock.entry(name).or_default().push(data);
+            result.push(data);
         }
-        lock.remove(name).unwrap_or_default()
+        result
+    }
+}
+
+
+impl SlowJobPool {
+    pub fn new() -> Self {
+        let (sender,receiver) = crossbeam_channel::unbounded();
+        Self {
+            next_id: AtomicU64::new(0),
+            groups: RwLock::new(HashMap::new()),
+            queue: RwLock::new(HashMap::new()),
+            finished: RwLock::new(HashMap::new()),
+            running_jobs: RwLock::new(HashMap::new()),
+            receiver,
+            sender,
+            global_limit: Box::new(|n| n/2 + n/4),
+        }
+    }
+
+    pub fn get<D>(&self, name: &str) -> Arc<SlowJobGroup<D>> where D: Sized + Send + 'static {
+        let lock = self.groups.write().unwrap();
+        if let Some(group) = lock.get(name) {
+            if group.type_id() == Arc<SlowJobGroup<Box>>
+        };
+        panic!("Unconfigured group name!");
     }
 
     fn maintain(&self) {