diff --git a/tools/opensnoop.py b/tools/opensnoop.py
index 5df3b41..e6fcb07 100755
--- a/tools/opensnoop.py
+++ b/tools/opensnoop.py
@@ -10,10 +10,12 @@
 # Licensed under the Apache License, Version 2.0 (the "License")
 #
 # 17-Sep-2015   Brendan Gregg   Created this.
+# 29-Apr-2016   Allan McAleavy updated for BPF_PERF_OUTPUT
 
 from __future__ import print_function
 from bcc import BPF
 import argparse
+import ctypes as ct
 
 # arguments
 examples = """examples:
@@ -38,32 +40,67 @@
 # define BPF program
 bpf_text = """
 #include <uapi/linux/ptrace.h>
+#include <uapi/linux/limits.h>
+#include <linux/sched.h>
+
+struct val_t {
+    u32 pid;
+    u64 ts;
+    char comm[TASK_COMM_LEN];
+    const char *fname;
+};
+
+struct data_t {
+    u32 pid;
+    u64 ts;
+    u64 delta;
+    int ret;
+    char comm[TASK_COMM_LEN];
+    char fname[NAME_MAX];
+};
 
 BPF_HASH(args_filename, u32, const char *);
+BPF_HASH(infotmp, u32, struct val_t);
+BPF_PERF_OUTPUT(events);
 
-int kprobe__sys_open(struct pt_regs *ctx, const char __user *filename)
+int trace_entry(struct pt_regs *ctx, const char __user *filename)
 {
+    struct val_t val = {};
     u32 pid = bpf_get_current_pid_tgid();
 
     FILTER
-    args_filename.update(&pid, &filename);
+    if (bpf_get_current_comm(&val.comm, sizeof(val.comm)) == 0) {
+        val.pid = bpf_get_current_pid_tgid();
+        val.ts = bpf_ktime_get_ns();
+        val.fname = filename;
+        infotmp.update(&pid, &val);
+    }
 
     return 0;
 };
 
-int kretprobe__sys_open(struct pt_regs *ctx)
+int trace_return(struct pt_regs *ctx)
 {
-    const char **filenamep;
-    int ret = ctx->ax;
     u32 pid = bpf_get_current_pid_tgid();
+    struct val_t *valp;
+    struct data_t data = {};
 
-    filenamep = args_filename.lookup(&pid);
-    if (filenamep == 0) {
+    u64 tsp = bpf_ktime_get_ns();
+
+    valp = infotmp.lookup(&pid);
+    if (valp == 0) {
         // missed entry
         return 0;
     }
+    bpf_probe_read(&data.comm, sizeof(data.comm), valp->comm);
+    bpf_probe_read(&data.fname, sizeof(data.fname), (void *)valp->fname);
+    data.pid = valp->pid;
+    data.delta = tsp - valp->ts;
+    data.ts = tsp / 1000;
+    data.ret = ctx->ax;
 
-    bpf_trace_printk("%d %s\\n", ret, *filenamep);
+    events.perf_submit(ctx, &data, sizeof(data));
+    infotmp.delete(&pid);
     args_filename.delete(&pid);
 
     return 0;
@@ -79,34 +116,68 @@
 
 # initialize BPF
 b = BPF(text=bpf_text)
+b.attach_kprobe(event="sys_open", fn_name="trace_entry")
+b.attach_kretprobe(event="sys_open", fn_name="trace_return")
+
+TASK_COMM_LEN = 16    # linux/sched.h
+NAME_MAX = 255        # linux/limits.h
+
+class Data(ct.Structure):
+    _fields_ = [
+        ("pid", ct.c_ulonglong),
+        ("ts", ct.c_ulonglong),
+        ("delta", ct.c_ulonglong),
+        ("ret", ct.c_int),
+        ("comm", ct.c_char * TASK_COMM_LEN),
+        ("fname", ct.c_char * NAME_MAX)
+    ]
+
+start_ts = 0
+prev_ts = 0
+delta = 0
 
 # header
 if args.timestamp:
     print("%-14s" % ("TIME(s)"), end="")
 print("%-6s %-16s %4s %3s %s" % ("PID", "COMM", "FD", "ERR", "PATH"))
 
-start_ts = 0
-
-# format output
-while 1:
-    (task, pid, cpu, flags, ts, msg) = b.trace_fields()
-    (ret_s, filename) = msg.split(" ", 1)
-
-    ret = int(ret_s)
-    if (args.failed and (ret >= 0)):
-        continue
+# process event
+def print_event(cpu, data, size):
+    event = ct.cast(data, ct.POINTER(Data)).contents
+    global start_ts
+    global prev_ts
+    global delta
+    global cont
 
     # split return value into FD and errno columns
-    if ret >= 0:
-        fd_s = ret
+    if event.ret >= 0:
+        fd_s = event.ret
         err = 0
     else:
-        fd_s = "-1"
-        err = - ret
+        fd_s = -1
+        err = - event.ret
 
-    # print columns
+    if start_ts == 0:
+        prev_ts = start_ts
+
+    if start_ts == 1:
+        delta = float(delta) + (event.ts - prev_ts)
+
+    if (args.failed and (event.ret >= 0)):
+        start_ts = 1
+        prev_ts = event.ts
+        return
+
     if args.timestamp:
-        if start_ts == 0:
-            start_ts = ts
-        print("%-14.9f" % (ts - start_ts), end="")
-    print("%-6d %-16s %4s %3s %s" % (pid, task, fd_s, err, filename))
+        print("%-14.9f" % (delta / 1000000), end="")
+
+    print("%-6d %-16s %4d %3d %s" % (event.pid, event.comm,
+        fd_s, err, event.fname))
+
+    prev_ts = event.ts
+    start_ts = 1
+
+# loop with callback to print_event
+b["events"].open_perf_buffer(print_event)
+while 1:
+    b.kprobe_poll()