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How about we change the -verbose:gc dump format but have some kind of<br>
compatibility mode, e.g., -verbose:gc:old?<br>
<br>
The problem with the current verbose:gc format from a development
engineering<br>
perspective pov is that many customers use it in production and forward
verbose:gc<br>
logs to us as part of bug reports or performance conversations. The
current format<br>
is pretty useless for either purpose, so we suspect it'd be better for
most customers<br>
for it to be enhanced.<br>
<br>
Paul<br>
<br>
Jon Masamitsu wrote:
<blockquote cite="mid:47F6406C.3020203@sun.com" type="cite">
<pre wrap="">James Nichols wrote On 04/04/08 05:27,:
</pre>
<blockquote type="cite">
<pre wrap="">I'd rather not have the format of the log changed, but simplifying the
arguments would be great. Isn't that the only change being proposed?
</pre>
</blockquote>
<pre wrap=""><!---->
At the end of the mail there was a suggestion to use the format for
PrintGCDetails
whenever -verbosegc was turned on. Currently the format for -verbosegc
output
is a shorter form (same as the PrintGC output). By my count we've only
seen
responses asking that it not change.
</pre>
<blockquote type="cite">
<pre wrap="">Doesn't everyone have a Perl script that they use to pull out the
stuff from the log that's relevant and put it in gnuplot or Excel or
something?
</pre>
</blockquote>
<pre wrap=""><!---->
We are trying to open source a tool that we call GChisto that takes the
PrintGCDetails (also PrintGC) output and plots some of it. Lots of
paperwork. We're not there yet.
</pre>
<blockquote type="cite">
<pre wrap="">Jim
On Fri, Apr 4, 2008 at 3:46 AM, Michael Finocchiaro
<<a class="moz-txt-link-abbreviated" href="mailto:michael.finocchiaro@gmail.com">michael.finocchiaro@gmail.com</a> <a class="moz-txt-link-rfc2396E" href="mailto:michael.finocchiaro@gmail.com"><mailto:michael.finocchiaro@gmail.com></a>>
wrote:
That is good idea to make PGCTS the default with PGCD and I also
agree that the TraceClassUnloading is annoying in a gc log.
I would propose that you look at HP's JVM GC log format as
something far easier to parse than the current format.
<a class="moz-txt-link-freetext" href="http://docs.hp.com/en/5992-1918/ch01s25.html">http://docs.hp.com/en/5992-1918/ch01s25.html</a>
or perhaps the jstatd format.
After about 5 or 6 years I can almost eyeball the current file
format but a numeric based, space or comma-separated list of the
GC cause and the memory space allocations would be a lot easier
for post-mortem diagnosis and tuning. And, at least in the HP
case, the overhead is very minimal (you get almost the same amount
of detail as from -XX:+PrintTenuringDistribution in a single
line)...and since there still is not a robust and easy-to-use
equivalent of HPjmeter (disclosure - I worked for 10 years for HP)
for analyzing the JavaSoft HotSpot JVMs, this would be an improvement.
My 2 cents,
Fino
On Thu, Apr 3, 2008 at 11:22 PM, Tony Printezis
<<a class="moz-txt-link-abbreviated" href="mailto:tony.printezis@sun.com">tony.printezis@sun.com</a> <a class="moz-txt-link-rfc2396E" href="mailto:tony.printezis@sun.com"><mailto:tony.printezis@sun.com></a>> wrote:
We're proposing a few small changes (and on significant one)
to the way
the GC logging flags work:
a) When +PrintGCDetails is set, +PrintGCTimeStamps should be
set by
default (currently, it has to be set explicitly; what we've
found is
that it's always more useful to have the time stamps in a GC
log when
analyzing it)
b) When -XXloggc: is set, +PrintGCDetails and
+PrintGCTimeStamps are set
automatically (instead of -verbosegc and +PrintGCTimeStamps)
(again, for
us, it's always more useful to have the more detailed
+PrintGCDetails
output in the log when analyzing it)
c) When -verbosegc, +PrintGCDetails, or -Xloggc: are set,
+TraceClassUnloading is _not_ automatically set, as it is now (it
polutes the output a bit during Full GCs)
Notice that, for the above, you'll still be able to get the
old behavior
by setting / unsetting some flags; we're just trying to set more
sensible defaults.
The more significant proposal:
d) Eliminate the -verbosegc format in favor of the (more
detailed and
more useful, though less concise) +PrintGCDetails format. Do
people
still heavily use and rely on the -verbosegc format in a way that
migration to the +PrintGCDetails format will be difficult?
Your thoughts and feedback on the above will be appreciated.
Thank you,
Tony, HS GC Group
--
----------------------------------------------------------------------
| Tony Printezis, Staff Engineer | Sun Microsystems Inc.
|
| | MS BUR02-311
|
| e-mail: <a class="moz-txt-link-abbreviated" href="mailto:tony.printezis@sun.com">tony.printezis@sun.com</a>
<a class="moz-txt-link-rfc2396E" href="mailto:tony.printezis@sun.com"><mailto:tony.printezis@sun.com></a> | 35 Network Drive
|
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Michael Finocchiaro
<a class="moz-txt-link-abbreviated" href="mailto:michael.finocchiaro@gmail.com">michael.finocchiaro@gmail.com</a> <a class="moz-txt-link-rfc2396E" href="mailto:michael.finocchiaro@gmail.com"><mailto:michael.finocchiaro@gmail.com></a>
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<pre wrap=""><!---->
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