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Hi Tony,<br>
<br>
I agree with your comments. Thanks for fixing this!<br>
<br>
One answer at the end of this message...<br>
<br>
<div class="moz-cite-prefix">On 2015-06-18 15:50, Tony Printezis
wrote:<br>
</div>
<blockquote
cite="mid:etPan.5582cc8d.1bcb7375.1215a@tw-mbp-tprintezis"
type="cite">
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style="font-family:Helvetica,Arial;font-size:13px; color:
rgba(0,0,0,1.0); margin: 0px; line-height: auto;">Hi Bengt,</div>
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style="font-family:Helvetica,Arial;font-size:13px; color:
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<div id="bloop_customfont"
style="font-family:Helvetica,Arial;font-size:13px; color:
rgba(0,0,0,1.0); margin: 0px; line-height: auto;">Thanks for
looking at it. Inline.</div>
<br>
<p class="airmail_on" style="color:#000;">On June 18, 2015 at
3:02:45 AM, Bengt Rutisson (<a moz-do-not-send="true"
href="mailto:bengt.rutisson@oracle.com">bengt.rutisson@oracle.com</a>)
wrote:</p>
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<div class="moz-cite-prefix"><br>
Hi Tony,<br>
<br>
NIce to hear from you!<br>
<br>
<br>
On 18/06/15 00:30, Tony Printezis wrote:<br>
</div>
<blockquote
cite="mid:etPan.5581f51b.699a1ea0.1215a@tw-mbp-tprintezis"
type="cite">
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color: rgb(0, 0,
0); margin: 0px;">Hi all,</div>
<div id="bloop_customfont" style="font-family:
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0); margin: 0px;"><br>
</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color: rgb(0, 0,
0); margin: 0px;">A small patch for your
consideration:</div>
<div id="bloop_customfont" style="font-family:
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0); margin: 0px;"><br>
</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color: rgb(0, 0,
0); margin: 0px;"><a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Etonyp/8086056/webrev.0/">http://cr.openjdk.java.net/~tonyp/8086056/webrev.0/</a></div>
</blockquote>
<br>
A couple of style comments:<br>
<br>
891 const size_t MinOldGenCapacity = G;<br>
892 const size_t MaxOldGenCapacity = 16 * G;<br>
893 assert(MinOldGenCapacity <= MaxOldGenCapacity,
"sanity");<br>
<br>
Local variables are normmaly named using lower case and
underscore.<span class="Apple-converted-space"> </span></div>
</div>
</span></blockquote>
</div>
<p><br>
</p>
<p>Yeah, I of course usually do that. But as they are constants I
thought I’d make them look like constants. :-)</p>
<p><br>
</p>
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<div>So, min_old_gen_capacity and
max_old_gen_capacity. Same for the rest of the local
variables in
ParNewGeneration::adjust_cards_per_stride().<br>
<br>
Having said that, I think it would be good to turn
some of these constants into flags (which means that
the naming should be as it is now ;) ).<span
class="Apple-converted-space"> </span></div>
</div>
</span></blockquote>
</div>
<p><br>
</p>
<p>Hang on! Are you and Masa encourating me to add 5 (!!!)
more cmd line args to HotSpot? ;-)</p>
<p><br>
</p>
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<div>Especially since you say that you haven't done
much performance testing of these values.</div>
</div>
</span></blockquote>
</div>
</div>
<p><br>
</p>
<p>To be clear: I did performance testing with chunks sizes in
the 256-8k range and with three old gen sizes (2g, 10g, and
20g) and auto-tuning comes pretty close to optimal; I have
numbers on the JIRA. But, yes, that was only with a couple of
(synthetic) tests and only on one architecture (Linux/x64). If
someone there could try this on a couple more apps and maybe
on sparc, as we don’t happen to have any sparc boxes lying
around :-), it’d be helpful.</p>
<p>But, yes, your suggestion of making the chunk size / old gen
capacity limits into cmd line args definitely makes sense and
I had also considered that myself. But I had decided against
it as I thought you wouldn’t want more cmd line args. :-) How
about:</p>
<p>+UseDynamicParGCStrides</p>
<p>DynamicParGCStrides{Min,Max}OldGenCapacity</p>
<p>DynamicParGCStrides{Min,Max}Size</p>
<p>I should also make them all manageable.</p>
<p><br>
</p>
<div>
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<div><span class="Apple-converted-space"> </span>I
would prefer that we could adjust them at runtime.
Best would of course be if you could take the time
to do the performance testing.</div>
</div>
</span></blockquote>
</div>
<p><br>
</p>
<p>So, as I said earlier, I did. The numbers are on the JIRA.
Is there anything else I could maybe run? Maybe larger old
gen than 20g? (but that’s reaching the memory limits of my
workstation, FWIW)</p>
<p><br>
</p>
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<div><br>
I realize that the assert on line 893 might have
been useful if you were playing around with the
numbers when you were experimenting with the
patch. But now it looks mostly like line noise to
me. Same with the assert on line 898.</div>
</div>
</span></blockquote>
</div>
<p><br>
</p>
<p>Actually, it as basically stating the invariant for those
parameters (in case someone wants to play around with
them). But if we make the constants into cmd line args
this will go away...</p>
<p><br>
</p>
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<div><br>
I would also consider factoring the actual
computation out into a separate helper method.</div>
</div>
</span></blockquote>
</div>
<p><br>
</p>
<p>You mean the interpolation? Like:</p>
<p>(base_min, base_max, value_min, value_max, value) ->
result in range [base_min, base_max]?</p>
</div>
</div>
</div>
</div>
</blockquote>
<br>
Yes, that's what I meant. But if you, as suggested above, get rid of
most (all?) of the constant definitions in adjust_cards_per_stride()
then I guess it is mostly only the interpolation left. So, in that
case it may not be necessary to factor it out. I would have to see a
new webrev to have more comments.<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<blockquote
cite="mid:etPan.5582cc8d.1bcb7375.1215a@tw-mbp-tprintezis"
type="cite">
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<p>Tony</p>
<p><br>
</p>
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<div><br>
I also second Jon's comment on that it would be
good with a more explicit way of turning this
feature off.<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<blockquote
cite="mid:etPan.5581f51b.699a1ea0.1215a@tw-mbp-tprintezis"
type="cite">
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</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color:
rgb(0, 0, 0); margin: 0px;">(BTW, for some
reason some of the webrev output is a bit
messed up. Not sure why, maybe some hg
incompatibility I guess. The diffs look OK
though. I also attached the patch to this
e-mail.)</div>
<div id="bloop_customfont" style="font-family:
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</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color:
rgb(0, 0, 0); margin: 0px;">There’s a bit of
info on the JIRA on the rationale for the
patch:</div>
<div id="bloop_customfont" style="font-family:
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rgb(0, 0, 0); margin: 0px;"><br>
</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color:
rgb(0, 0, 0); margin: 0px;"><a
moz-do-not-send="true"
href="https://bugs.openjdk.java.net/browse/JDK-8086056">https://bugs.openjdk.java.net/browse/JDK-8086056</a></div>
<div id="bloop_customfont" style="font-family:
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</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color:
rgb(0, 0, 0); margin: 0px;">The min / max
values for the old gen capacity
and ParGCCardsPerStrideChunk were chosen
empircally after running a few (mostly
synthetic tests) on Linux x64. If someone
has the cycles to do a more extensive
performance study, I’d be happy to revise
them accordingly.</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color:
rgb(0, 0, 0); margin: 0px;"><br>
</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color:
rgb(0, 0, 0); margin: 0px;">Regards,</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color:
rgb(0, 0, 0); margin: 0px;"><br>
</div>
<div id="bloop_customfont" style="font-family:
Helvetica, Arial; font-size: 13px; color:
rgb(0, 0, 0); margin: 0px;">Tony</div>
<br>
<div id="bloop_sign_1434579909530055936"
class="bloop_sign">
<div style="font-family: helvetica, arial;
font-size: 13px;">
<div>-----</div>
<div><br>
</div>
<div>Tony Printezis | JVM/GC Engineer / VM
Team | Twitter</div>
<div><br>
</div>
<div>@TonyPrintezis</div>
<div><a moz-do-not-send="true"
href="mailto:tprintezis@twitter.com">tprintezis@twitter.com</a></div>
<div><br>
</div>
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</span></blockquote>
<br class="Apple-interchange-newline">
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<br class="Apple-interchange-newline">
</div>
<br class="Apple-interchange-newline">
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<br class="Apple-interchange-newline">
</div>
<br class="Apple-interchange-newline">
</div>
<div id="bloop_sign_1434634117464453888" class="bloop_sign">
<div style="font-family:helvetica,arial;font-size:13px">
<div>-----</div>
<div><br>
</div>
<div>Tony Printezis | JVM/GC Engineer / VM Team | Twitter</div>
<div><br>
</div>
<div>@TonyPrintezis</div>
<div><a moz-do-not-send="true"
href="mailto:tprintezis@twitter.com">tprintezis@twitter.com</a></div>
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