some bcc examples and tools
diff --git a/examples/bitehist.c b/examples/bitehist.c
new file mode 100644
index 0000000..e4e6772
--- /dev/null
+++ b/examples/bitehist.c
@@ -0,0 +1,48 @@
+/*
+ * bitehist.c Block I/O size histogram.
+ * For Linux, uses BCC, eBPF. See .py file.
+ *
+ * Based on eBPF sample tracex2 by Alexi Starovoitov.
+ * Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * 15-Aug-2015 Brendan Gregg Created this.
+ */
+
+#include <uapi/linux/ptrace.h>
+#include "../../linux-4.2-rc5/include/linux/blkdev.h"
+
+BPF_TABLE("array", int, u64, dist, 64);
+
+static unsigned int log2(unsigned int v)
+{
+ unsigned int r;
+ unsigned int shift;
+
+ r = (v > 0xFFFF) << 4; v >>= r;
+ shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
+ shift = (v > 0xF) << 2; v >>= shift; r |= shift;
+ shift = (v > 0x3) << 1; v >>= shift; r |= shift;
+ r |= (v >> 1);
+ return r;
+}
+
+static unsigned int log2l(unsigned long v)
+{
+ unsigned int hi = v >> 32;
+ if (hi)
+ return log2(hi) + 32 + 1;
+ else
+ return log2(v) + 1;
+}
+
+int do_request(struct pt_regs *ctx, struct request *req)
+{
+ int index = log2l(req->__data_len / 1024);
+ u64 *leaf = dist.lookup(&index);
+ if (leaf) (*leaf)++;
+
+ return 0;
+}