<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><br><div><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix"><font size="-1"><tt>
<br>
The correlation between young gc pause and occupancy in
tenure, might be related to Remember Set operations.</tt></font></div></div></blockquote><div><br></div>It certainly related to RSet operations.</div><div><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix"><font size="-1"><tt> Do you
see ScanRS/UpdateRS goes up with the tenure occupancy is high?<br>
<br>
If the occupancy of a region in old gen is higher than
G1MixedLiveThresholdPercent(default 65 before 8u40, 85 8u40
and later), then it is not considered as a candidate for cset.<br></tt></font></div></div></blockquote><div><br></div>Indeed and I’m wondering if this should be elastic or reactive to current conditions. IOWs, if memory pressure is low I might be tolerant of collecting these low value targets in that if enough of them have dead objects in them in a large heap there still might be value in collecting them outside of running a full gc.</div><div><br></div><div>Regards,</div><div>Kirk</div><div><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix"><font size="-1"><tt>
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<pre class="moz-signature" cols="72">Thanks,
Jenny</pre>
On 6/2/2015 5:19 AM, Kirk Pepperdine wrote:<br>
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<blockquote cite="mid:BE60A11D-6528-4B5C-A17F-DE187FD26300@kodewerk.com" type="cite">Hi,
<div><br>
</div>
<div>I can show you a direct correlation between young gen pauses
and occupancy of Tenured. In fact please find attached graphs
from work I did on Monday. What I do know is that under normal
operations there are regions that I wished could be collected
that can’t be collected. I say this because they don’t meet the
thresholds to be included in the CSet. That said, the amount of
dead in each of the tenured regions is enough that overall there
is a visible negative effect on GC pause times. So, I think I'd
like a continuous concurrent cleaning of tenured regions or
something else that I’ve not quite thought through just yet.
What I do know is that if I run a full gc, the pause time
picture clears up because the regions that wouldn’t get
collected do and that reduces the “live set”. Some where tucked
away I’ve got others logs that demonstrate this effect. I’ll see
if I can dig it up.</div>
<div><br>
</div>
<div>Regards,</div>
<div>Kirk</div>
<div>PS, once we’re finished with this conversation I’d like to
tackle safe-pointing behavior. I think Charlie knows what I’m
talking about.</div>
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