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Hi Staffan,<br>
<br>
psPromotionManager.inline.hpp<br>
<br>
I think the PSPromotionManager::copy_to_survivor_space() might send
multiple events. If the allocation to the young gen fails we will
fall through to do an old gen allocation. But we send the events
before we realize that the allocation has failed, i.e. new_obj is
NULL.<br>
<br>
I talked to Erik a bit about how to handle the gc_tracer in
par_promote. He'll get back to you with some thoughts on that.<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<br>
<div class="moz-cite-prefix">On 2014-09-06 00:20, Staffan Friberg
wrote:<br>
</div>
<blockquote cite="mid:540A3730.1060603@oracle.com" type="cite">
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<div class="moz-cite-prefix">Hi,<br>
<br>
I have uploaded a new webrev here,
cr.openjdk.java.net/~sfriberg/8055845/webrev.03<br>
<br>
It contains several changes<br>
<br>
- Split event into two events (PromoteObjectInNewPLAB,
PromoteObjectOutsidePLAB)<br>
- Moved events to "vm/gc/detailed/PromoteObject..."<br>
- Supporting ParNew+CMS and ParNew+SerialOld tenuring<br>
- Not sure if the way I do it with passing the
ParNewTracer is the best solution, please let me know if you
have an idea how to improve it<br>
- Simplified the G1 code to avoid sending age and having a
single call site<br>
- Fixed so that the generated event has size information in
bytes rather than words<br>
<br>
Thanks for offline comments and suggestions from Dmitry and
Thomas.<br>
<br>
Cheers,<br>
Staffan<br>
<br>
On 08/29/2014 03:32 PM, Staffan Friberg wrote:<br>
</div>
<blockquote cite="mid:5400FF6F.5040203@oracle.com" type="cite">
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<div class="moz-cite-prefix">Hi Erik,<br>
<br>
On 08/28/2014 11:34 PM, Erik Helin wrote:<br>
</div>
<blockquote cite="mid:54001EFF.3030802@oracle.com" type="cite">(it
seems like we lost <a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:hotspot-gc-dev@openjdk.java.net">hotspot-gc-dev@openjdk.java.net</a>
somewhere in this thread, I'm adding it back) <br>
<br>
On 2014-08-28 23:15, Staffan Friberg wrote: <br>
<blockquote type="cite">Hi Erik, <br>
<br>
Thanks for the comments. <br>
<blockquote type="cite">- Aren't the events for promotion to
the tenured generation (SerialOld) <br>
and the CMS generation missing? <br>
</blockquote>
The reason for leaving out these two, Serial completely and
CMS <br>
promotion, was due to that neither as far as I understand
make use of <br>
PLABs. <br>
</blockquote>
<br>
I might be wrong here, but looking at the function
TenuredGeneration::par_promote (in tenuredGeneration.cpp) it
looks to me like SerialOld is using PLABs when ParNew is
promoting objects from young to old. <br>
<br>
As for CMS, looking at
ConcurrentMarkSweepGeneration::par_promote (in
concurrentMarkSweepGeneration.cpp) it seems like each
CMSParGCThreadState has a CFLS_LAB (CompactibleFreeListSpace
Local Allocation Buffer) that is a thread-local allocation
buffer. See compactibleFreeListSpace.{hpp,cpp} for more
details. <br>
<br>
Given this, I think we should add events for Serial and CMS as
well. <br>
<br>
</blockquote>
<br>
Ok I see what you mean with CMS, basically the equivalent to
getting a PLAB would be when we refill the CFLS_LAB in the alloc
function. It still does the allocation to a small memory (~ size
of object) area from the freelist, but at least we did extra
work to refill the local CFLS_LAB. Need to do some analysis to
see how often we refill so the overhead doesn't get too high.<br>
The only issue I run into is how I can in a nice way get access
to the ParNewTracer from ParNewGeneration to call the report
function. Let's sync up next week and see how it can be solved.<br>
<br>
The tenured GC requires something similar to be supported,
however since ParNewGC is deprecated for usage without CMS in
JDK 8 we might want to skip that combination.<br>
<br>
<br>
<blockquote cite="mid:54001EFF.3030802@oracle.com" type="cite">
<br>
On 2014-08-28 23:15, Staffan Friberg wrote: <br>
<blockquote type="cite">
<blockquote type="cite">- Would it make sense to
differentiate, either by separate events or by <br>
a field in a event, between promotions to to-space and
to the old <br>
generation? <br>
- The are two events for TLAB allocations, <br>
java/object_alloc_in_new_TLAB and
java/object_alloc_outside_TLAB. <br>
What do you think about using two events for PLAB
allocations as well: <br>
- java/object_alloc_in_new_PLAB <br>
- java/object_alloc_outside_PLAB <br>
</blockquote>
I think this is a matter of taste and probably how similar
we want the <br>
event to be to the existing allocation event. I personally
prefer a <br>
single event but if the GC team and serviceability team feel
it would be <br>
better to have two I can certainly rewrite. The reason for
me preferring <br>
a single event is just ease of analysis, you can easily
filter a list of <br>
events on a field, it is harder to merge two different
events with <br>
different fields and work with them in an straight forward
fashion. <br>
<br>
Any general preference for having a single or multiple
events? <br>
</blockquote>
<br>
I would prefer to have two events in this case and try to
follow the existing allocation events as much as possible
(both in naming and in style). Keeping the tenured field (I
missed it the first time I read the patch) is good. <br>
<br>
</blockquote>
Yes, tenured would be independent of having two events, only
PLAB size and directAllocation would be affected when having two
event types.<br>
<br>
<b>Erik Gahlin</b>, any preference from your end?<br>
<br>
<br>
<br>
<blockquote cite="mid:54001EFF.3030802@oracle.com" type="cite">On
2014-08-28 23:15, Staffan Friberg wrote: <br>
<blockquote type="cite">
<blockquote type="cite">- In PSPromotionManager, instead of
utilizing the C++ friendship with <br>
PSScavenge, should we add a getter function for the
gc_tracer? <br>
</blockquote>
Created a getter function. <br>
</blockquote>
<br>
Thanks! If you make report_promotion_sample const, then the
getter can return a const ParallelScavengeTracer*, right? <br>
<br>
</blockquote>
Done<br>
<br>
//Staffan<br>
</blockquote>
<br>
</blockquote>
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