Write lockstat results to the lockstat.last file

8d482ffb · Silas Boyd-Wickizer · 8312d2c6 · 8d482ffb
--- a/lockstat.cc
+++ b/lockstat.cc
@@ -17,14 +17,21 @@ stats(void)
 {
  static const u64 sz = sizeof(struct lockstat);
  struct lockstat ls;
-  int fd;
+  int sfd, fd;
  int r;

  fd = open("/dev/lockstat", O_RDONLY);
  if (fd < 0)
    die("lockstat: open failed");

+  unlink("/lockstat.last");
+  sfd = open("/lockstat.last", O_RDWR|O_CREATE);
+  if (sfd < 0)
+    die("lockstat: open failed");
+
  printf(1, "## name acquires contends locking locked\n");
+  printf(sfd, "## name acquires contends locking locked\n");
+  
  while (1) {
    r = read(fd, &ls, sz);
    if (r < 0)
@@ -43,10 +50,15 @@ stats(void)
      locking += ls.cpu[i].locking;
      locked += ls.cpu[i].locked;
    }
-    if (contends > 0)
+    if (contends > 0) {
      printf(1, "%s %lu %lu %lu %lu\n", 
             ls.name, acquires, contends, locking, locked);
+      printf(sfd, "%s %lu %lu %lu %lu\n", 
+             ls.name, acquires, contends, locking, locked);
+    }
  }
+
+  close(sfd);
 }

 int