Guarantee gc threads try to run at least once a second.

I might have broken something, but gc threads were running too infrequently for testing. A gc thread might run at a higher rate due to the heuristic in gc_end_epoch.

Guarantee gc threads try to run at least once a second.
553de92d · Silas Boyd-Wickizer · aed48c5c · 553de92d · 553de92d · 553de92d
--- a/cpu.h
+++ b/cpu.h
@@ -10,7 +10,6 @@ struct cpu {
  struct segdesc gdt[NSEGS];   // x86 global descriptor table
  struct taskstate ts;         // Used by x86 to find stack for interrupt
  struct context *scheduler;   // swtch() here to enter scheduler
-  u64 last_rcu_gc_ticks;
  struct wqframe *wqframe;

  // Cpu-local storage variables; see below

--- a/gc.c
+++ b/gc.c
@@ -238,14 +238,6 @@ gc_delayed2(int a1, u64 a2, void (*dofree)(int,u64))
 }

 void
-gc_start(void)
-{
-  // XXX hack?
-  if (gc_state[mycpu()->id].cnt++ % 10000 == 0)
-    cv_wakeup(&gc_state[mycpu()->id].cv);
-}
-
-void
 gc_begin_epoch(void)
 {
  if (myproc() == NULL) return;
@@ -266,8 +258,7 @@ gc_end_epoch(void)
  --myproc()->epoch_depth;
  release(&myproc()->gc_epoch_lock);
  if (myproc()->epoch_depth == 0 && gc_state[mycpu()->id].ndelayed > NGC) 
-    gc_start();
-
+    cv_wakeup(&gc_state[mycpu()->id].cv);
 }

 void gc_dumpstat(void)
@@ -290,7 +281,7 @@ gc_worker(void *x)
  for (;;) {
    u64 i;
    acquire(&wl);
-    cv_sleep(&gc_state[mycpu()->id].cv, &wl);  
+    cv_sleepto(&gc_state[mycpu()->id].cv, &wl, nsectime() + 1000000000);
    release(&wl);
    gc_state[mycpu()->id].nrun++;
    u64 global = global_epoch;

--- a/proc.c
+++ b/proc.c
@@ -370,12 +370,6 @@ scheduler(void)
      }
    }

-    int now = ticks;
-    if (now - mycpu()->last_rcu_gc_ticks > 100) {
-      gc_start();
-      mycpu()->last_rcu_gc_ticks = now;
-    }
-
    if (idle[mycpu()->id]) {
      int worked;
      do {