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Hello Bengt,<br>
<br>
I am going to try out the new logging myself but some quick feedback
from the examples output you had provided:<br>
<br>
<b>-Xlog:gc:</b><br>
<br>
1. It is great to have the start and end timestamps included on the
same GC log line.<br>
<br>
2.<br>
<pre><i>[0.643s][info ][gc] GC#5 GC young (G1 Evacuation Pause) end 91M->61M(128M) (0.632s, 0.643s) 11.399ms</i><i>
</i><i>[1.499s][info ][gc] GC#16 GC remark end 73M->73M(128M) (1.486s, 1.499s) 12.545ms
[1.500s][info ][gc] GC#16 GC cleanup end 73M->73M(128M) (1.499s, 1.500s) 0.729ms</i>
</pre>
<br>
It does not make much of a sense here to include 'end' in the log
lines. If there is no line with a 'start' then I think it does not
serve any purpose to have 'end' for these GC lines.<br>
<br>
3. There are some white-spaces after the 'level' ([info ]), it'd
be good if those can be removed.<br>
<br>
<b>-Xlog:gc*</b><b>:</b><br>
<br>
1. Is there a specific reason to print the tag (gc) and other
sub-tags in different order? For example, we have 'start, gc', and
the order is different in 'gc, heap'.<br>
<i><a>
<pre>[1.300s][info ][start,gc ] GC#3 GC (Allocation Failure) DefNew start
[1.300s][info ][start,gc ] GC#4 Full GC (Allocation Failure) start
[2.154s][info ][gc ] GC#4 Full GC (Allocation Failure) end 93M->59M(123M) (1.300s, 2.154s) 854.130ms
[2.154s][info ][gc,heap ] GC#3 def new generation: 36767K->0K(39296K)
[2.154s][info ][gc,heap ] GC#3 tenured generation: 58893K->61204K(87424K)
[2.154s][info ][gc,metaspace] GC#3 Metaspace: 2953K->2953K(1056768K)</pre>
</a></i>if possible, I think we should have the order 'main-tag,
sub-tag' at all the places.<br>
<br>
Thanks,<br>
Poonam<br>
<br>
<div class="moz-cite-prefix">On 10/26/2015 5:26 AM, Bengt Rutisson
wrote:<br>
</div>
<blockquote cite="mid:562E1BE5.7090604@oracle.com" type="cite">
<br>
Hi again everyone,
<br>
<br>
An update on the work for JEP 271 Unified GC Logging.
<br>
<br>
I now have a working prototype that covers all GCs. Here are some
examples comparing the old format (using -XX:+PrintGC and
-XX:+PrintGCDetails) with the new format (using -Xlog):
<br>
<br>
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~brutisso/JEP-271/pre-review.00/compare.html">http://cr.openjdk.java.net/~brutisso/JEP-271/pre-review.00/compare.html</a>
<br>
<br>
The new logging format, using -Xlog, is much more flexible than
the old format. So, the comparison table on the above page is by
no means complete. I hope it will give a good overview, but to get
a real feel for how the new logging works I think it is necessary
to run locally and play around with the logging options.
<br>
<br>
Here is a webrev of the changes so far:
<br>
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~brutisso/JEP-271/pre-review.00/webrev.00/">http://cr.openjdk.java.net/~brutisso/JEP-271/pre-review.00/webrev.00/</a>
<br>
<br>
There is still work to do and I have some known issues with the
code changes. So, I am currently not asking for too much feedback
on the actual code changes. I am more looking for feedback on the
logging behavior. The webrev can be useful to get a feel for what
the code changes will look like but mostly I think it can be used
to apply the patch and build your own HotSpot to try out the new
logging.
<br>
<br>
Some changes based on the initial feedback:
<br>
- Start and end timestamps for the GC included on the GC log line.
<br>
- Printing the unit of a value without a space. I.e. "10.345ms"
instead of "10.345 ms". (Still working on fixing this in all
places as well as trying to use milliseconds instead of seconds in
as many places as possible.)
<br>
- Printing heap change information with a fixed unit. I am now
using M for overall heap transition and K for detailed information
on the debug level.
<br>
- Removed the "summary" tag. Instead the end logging for a GC
includes all relevant information.
<br>
<br>
All feedback is very welcome!
<br>
<br>
Thanks,
<br>
Bengt
<br>
</blockquote>
<br>
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