Hi Brendan,
We are aware of these issues and work with the Solaris team to fix them
in JDK 9.
One is the frame pointer is used by the server compiler as a general
purpose register on intel.
Another is about the virtual (or inlined) frames.
There are a couple of related bugs:
https://bugs.openjdk.java.net/browse/JDK-6617153
https://bugs.openjdk.java.net/browse/JDK-6276264
There can be more issues filed on this.
Please, note, that the jstack action is not implemented on Linux yet.
Thanks,
Serguei
On 6/16/14 5:14 PM, Brendan Gregg wrote:
Thanks but no, I'm aware of that bug and workarounds (I'm using the
LD_AUDIT_64=/usr/lib/dtrace/64/libdtrace_forceload.so workaround,
which isn't mentioned in the bug comments, but probably should be).
That bug is about missing symbols, but the stacks shown in that bug
still go all the way to thread_start. My stacks often don't.
For simple programs, the stacks are complete. But something complex
(eg, vert.x with event loops), and the stacks are often incomplete,
one frame only. Very much like what I see with -fomit-frame-pointer,
although this is hotspot, not gcc. Such incomplete stacks are seen
using either DTrace or perf_events.
It was suggested to me to email the hotspot developers, because this
may well be a hotspot optimization they are familiar with. It may also
be something really obvious, like that the JVM breaks native stacks
due to optimized frames / green threads / etc, and there is absolutely
no way around it (no way to disable it). If that's true, it may also
mean that the DTrace jstack() action has always had this issue. I'm
still reading the source...
Brendan
On Mon, Jun 16, 2014 at 4:04 AM, Staffan Larsen
<staffan.lar...@oracle.com <mailto:staffan.lar...@oracle.com>> wrote:
I think this is the bug you are looking at:
https://bugs.openjdk.java.net/browse/JDK-7187999, but I’ll defer
to someone else to confirm.
/Staffan
On 16 jun 2014, at 12:47, Roland Westrelin
<roland.westre...@oracle.com <mailto:roland.westre...@oracle.com>>
wrote:
Forwarding to serviceability alias where this question belongs I
think.
Begin forwarded message:
*From: *Brendan Gregg <brendan.d.gr...@gmail.com
<mailto:brendan.d.gr...@gmail.com>>
*Subject: **system profilers and incomplete stacks*
*Date: *June 12, 2014 at 7:15:54 PM GMT+2
*To: *hotspot-compiler-...@openjdk.java.net
<mailto:hotspot-compiler-...@openjdk.java.net>
G'Day,
Is there a way to run hotspot so that a system profiler (eg,
DTrace, or Linux perf_events) can measure complete stacks? I
often get incomplete, partial stacks, with one or a few frames
only. I'm not worried about symbols right now, what I'd like is
to walk stacks all the way down to thread start.
I've been browsing the hotspot code, but haven't found out how
yet. I suspect it's related to Java optimized frames, and has
ditched the frame pointer. I was looking for an equivalent
-fno-omit-frame-pointer option.
Here's an example:
# dtrace -n 'profile-99 /execname == "java"/ { @[jstack(100,
8000)] = count(); }'
[...]
org/mozilla/javascript/
ScriptableObject.createSlot(Ljava/lang/String;II)Lorg/mozilla/javascript/ScriptableObject$Slot;*
0x884acce8200002da
1
sun/nio/ch/SocketChannelImpl.read(Ljava/nio/ByteBuffer;)I*
0xffffffff20007f4b
1
org/mozilla/javascript/ScriptRuntime.newObjectLiteral([Ljava/lang/Object;[Ljava/lang/Object;[ILorg/mozilla/javascript/Context;Lorg/mozilla/javascript/Scriptable;)Lorg/mozilla/javascript/Scriptable;*
0xa20000041
1
[...]
I see similar incomplete stacks with Linux perf_events. Oracle
JDKs from 6 to 8, and OpenJDK.
thanks,
Brendan
--
http://www.brendangregg.com <http://www.brendangregg.com/>
--
http://www.brendangregg.com
