asharing vm2 test that does lots of non-commutative operations

The only unexpected sharing is on the VMA refcount, which is exactly what we expected.

asharing vm2 test that does lots of non-commutative operations
f51e9863 · Austin Clements · Silas Boyd-Wickizer · 69cbd10a · f51e9863
--- a/bin/asharing.cc
+++ b/bin/asharing.cc
@@ -9,6 +9,7 @@
 #include <sys/mman.h>
 #include "atomic.hh"
+#include <utility>
 static int cpu;
 std::atomic<int> barrier;
@@ -38,6 +39,14 @@ ready(void)
  }
 }
+u64
+rnd(void)
+{
+  static u64 rseed;
+  rseed = rseed * 6364136223846793005 + 1442695040888963407;
+  return rseed;
+}
 void*
 vmsharing(void* arg)
 {
@@ -55,6 +64,48 @@ vmsharing(void* arg)
  return 0;
 }
+std::atomic<int> round;
+void*
+vm2sharing(void *arg)
+{
+  u64 i = (u64) arg;
+  char *base = (char*)0x1000;
+  ready();
+  while (true) {
+    while (round % ncore != i)
+      asm volatile("pause");
+    if (round >= 50) {
+      round++;
+      return 0;
+    }
+    int op = rnd() % 2;
+    int lo = rnd() % 10, hi = rnd() % 10;
+    if (lo > hi)
+      std::swap(lo, hi);
+    if (lo == hi)
+      continue;
+    if (op == 0) {
+      // Map
+      void *res = mmap(base + lo * 4096, (hi-lo) * 4096, PROT_READ|PROT_WRITE,
+                       MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
+      if (res == MAP_FAILED)
+        die("asharing: mmap failed");
+    } else {
+      // Unmap
+      int res = munmap(base + lo * 4096, (hi-lo) * 4096);
+      if (res < 0)
+        die("asharing: munmap failed");
+    }
+    round++;
+  }
+}
 void*
 fssharing(void* arg)
 {
@@ -84,6 +135,8 @@ main(int ac, char **av)
  void* (*op)(void*) = 0;
  if (ac == 2 && strcmp(av[1], "vm") == 0)
    op = vmsharing;
+  else if (ac == 2 && strcmp(av[1], "vm2") == 0)
+    op = vm2sharing;
  else if (ac == 2 && strcmp(av[1], "fs") == 0)
    op = fssharing;
  else