Start of some kernel code that looks for userspace work

7e84b1c2 · Silas Boyd-Wickizer · a778a729 · 7e84b1c2 · 7e84b1c2 · 7e84b1c2
--- a/include/uwq.hh
+++ b/include/uwq.hh
@@ -4,5 +4,25 @@ struct padded_length {
 };
 #if defined (XV6_KERNEL)
+struct uwq_length {
+  uwq_length(padded_length *len) : len_(len) {}
+  void clear() {
+    for (int i = 0; i < NCPU; i++)
+      len_[i].v_ = 0;
+  }
+  bool haswork() {
+    for (int i = 0; i < NCPU; i++) {
+      if (len_[i].v_ > 0)
+        return true;
+    }
+    return false;
+  }
+private:
+  padded_length* len_;
+};
 int             uwq_trywork(void);
 #endif
--- a/include/vm.hh
+++ b/include/vm.hh
@@ -93,10 +93,10 @@ struct vmap {
  NEW_DELETE_OPS(vmap)
  uptr brk_;                    // Top of heap
+  padded_length* const uwq_len_;
 private:
  int pagefault_wcow(vma *m);
-  padded_length* const uwq_len_;
  struct spinlock brklock_;
 };
--- a/kernel/idle.cc
+++ b/kernel/idle.cc
@@ -118,7 +118,7 @@ idleloop(void)
          idlem->heir = p;
        }
-        worked = uwq_trywork();
+        // XXX(sbw) worked = uwq_trywork();
        worked = wq_trywork();
        // If we are no longer the idle thread, exit

--- a/kernel/uwq.cc
+++ b/kernel/uwq.cc
 #include "types.h"
+#include "amd64.h"
 #include "kernel.hh"
+#include "cpu.hh"
 #include "uwq.hh"
+#include "gc.hh"
+#include "percpu.hh"
+#include "spinlock.h"
+#include "condvar.h"
+#include "proc.hh"
+#include "vm.hh"
 int
 uwq_trywork(void)
 {
+  u64 i, k;
+  // A "random" victim CPU
+  k = rdtsc();
+  for (i = 0; i < NCPU; i++) {
+    u64 j = (i+k) % NCPU;
+    if (j == mycpuid())
+      continue;
+    struct cpu *c = &cpus[j];
+    scoped_gc_epoch();
+    struct proc *p = c->proc;
+    if (p == nullptr || p->vmap == nullptr)
+      continue;
+    padded_length *len = p->vmap->uwq_len_;
+    if (len == nullptr)
+      break;
+    if (uwq_length(len).haswork()) {
+      // XXX(sbw) start a worker thread..
+      break;
+    }
+  }
  return 0;
 }
--- a/kernel/vm.cc
+++ b/kernel/vm.cc
@@ -14,6 +14,7 @@
 #include "crange.hh"
 #include "cpputil.hh"
 #include "sperf.hh"
+#include "uwq.hh"
 enum { vm_debug = 0 };
@@ -162,6 +163,8 @@ vmap::vmap() :
  if (uwq_len_ == nullptr) {
    cprintf("vmap::vmap: userwq out of memory\n");
    goto err;
+  } else {
+    uwq_length(uwq_len_).clear();
  }
  if (setupuvm(pml4, kshared, (char*)uwq_len_)) {