Hi Gunter,
globals.hpp: fix typo "informatiuon"
I worry a little bit about the synchronizing (if that's the right word)
of PrintExtendedThreadInfo and the dcmd's -e flag. When using -e, you
are temporarily enabling PrintExtendedThreadInfo if it was false. This
temporarily changes the behavior of thread dumps, and could impact other
uses that happen in parallel. Also, could two simultaneous uses of -e
result in PrintExtendedThreadInfo not getting restored properly?
thread_dump() doesn't look right. It looks like you are iterating char
by char over the argument, and expect something like "-el" to be
specified rather then "-e -l". The loop should be iterating over
op->arg(i), not op->arg(0)[i].
The rest of the changes look fine.
thanks,
Chris
On 5/30/18 8:12 AM, Haug, Gunter wrote:
Hi all,
As Chris proposed, I have made an the extended output switchable. There is an
VM flag (PrintExtendedThreadInfo), which is false by default. Moreover, there
is an Option (-e) which can be used with jcmd Thread.print as well as with
jstack. The -e option essentially sets PrintExtendedThreadInfo true just for
the respective thread dump.
Here is the updated webrev:
http://cr.openjdk.java.net/~ghaug/webrevs/8200720.v2
(https://bugs.openjdk.java.net/browse/JDK-8200720)
Thanks,
Gunter
On 02.05.18, 17:07, "serviceability-dev on behalf of Haug, Gunter"
<serviceability-dev-boun...@openjdk.java.net on behalf of gunter.h...@sap.com> wrote:
Hi Chris,
Thanks for looking into this.
You're right, there is a little more we have. We have implemented an IO
tracing mechanism which - rather as a byproduct - keeps track of bytes read and
written per thread. However, this of course requires changes not only in
hotspot. We would be happy to contribute this as well, but this is a far bigger
change and will probably lead to a far bigger discussion. Anyway, with the
number of bytes read, the number of classes defined doesn't look that arbitrary
anymore, as one can correlate IO to class loading.
Regarding the verbose option I think that's a good idea!
Thanks again,
Gunter
On 01.05.18, 22:55, "Chris Plummer" <chris.plum...@oracle.com> wrote:
Hi Gunter,
The output you are adding is all useful. I think the question is (and
I'd like to see a few people chime in on this for this review) is
whether or not all of it is the appropriate for a thread's stack dump.
For example, defined_classes is on the fringe of what I would call
generally useful info in a stack dump. Sure, there might be that rare
case when you need it, but how often compared to other useful info
maintained on a per thread basis. How many other bits of useful info
are
not being printed in favor of defined_classes? It seems you have more
in
the queue. How many? I'm worried about how cluttered the stack dumps
will get. Maybe we should add some sort of verbose thread dumping
option. Just a thought.
As for the implementation, overall it looks good, but I can't speak to
whether or not you are doing proper accounting of defined_classes and
bytes allocated. You'll need input from someone with more knowledge of
those areas. We'll also need to do some testing to make sure tool tests
are not impacted.
thanks,
Chris
On 4/30/18 2:51 AM, Haug, Gunter wrote:
> Hi,
>
> this is an update to an RFR I posted on hotspot-dev, but it is
probably more suitable to post it here. Can I please have a review and a sponsor
for the following enhancement:
>
> http://cr.openjdk.java.net/~ghaug/webrevs/8200720.v1
> https://bugs.openjdk.java.net/browse/JDK-8200720
>
> We at SAP have extended the thread dumps (obtained by jstack or
jcmd) by several fields providing thread specific information. These extensions
are quite popular with our support team. With some knowledge of the architecture
of the application, they often allow for quick and simple diagnosis of a running
system. Therefore we would like to contribute these enhancements.
>
> I took a few simple examples here, namely cpu time, elapsed time
since thread creation, bytes allocated and classes defined by the thread and the
pthread-id or equivalent on platforms where it makes sense. Provided it is known
how the application should behave, a misbehaving thread can identified easily.
>
> There is no measurable overhead for this enhancement. However, it
may be a problem that the format of the output is changed. Tools parsing the
output may have to be changed.
>
> Here is an example of the output generated:
>
> ------------------------------------------------------
>
> "main" #1 prio=5 os_prio=31 cpu=6300.65ms elapsed=123.28s
allocated=242236760B defined_classes=1725 tid=0x00007fa13a806000 nid=0x1c03
pthread-id=0x109708000 waiting on condition [0x0000000109707000]
> java.lang.Thread.State: TIMED_WAITING (sleeping)
> JavaThread state: _thread_blocked
> Thread: 0x00007fa13a806000 [0x1c03] State: _at_safepoint
_has_called_back 0 _at_poll_safepoint 0
> JavaThread state: _thread_blocked
> at java.lang.Thread.sleep(java.base/Native Method)
> ...
> ------------------------------------------------------
>
> As mentioned above, we have a whole bunch of other enhancements to
the thread dump similar to this one and would be willing to contribute them if
there is any interest.
>
> Thanks and best regards,
> Gunter
>
>
