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Hi Staffan,<br>
<br>
<div class="moz-cite-prefix">On 2014-11-06 11:12, Staffan Friberg
wrote:<br>
</div>
<blockquote cite="mid:545B4986.1050700@oracle.com" type="cite">
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<div class="moz-cite-prefix">Hi,<br>
<br>
After further off list discussion it was decided to keep the
gc_tracer in par_promote as is.<br>
<br>
I have uploaded a new webrev, <a moz-do-not-send="true"
class="moz-txt-link-freetext"
href="http://cr.openjdk.java.net/%7Esfriberg/8055845/webrev.05">http://cr.openjdk.java.net/~sfriberg/8055845/webrev.05</a><br>
<br>
The main change here is a rewrite of the G1 code which is
cleaner and also reuses the read age. By sending the markOop
down through the call we can now trust the read age and do not
need to reread it when incrementing which improves the YC
performance slightly as it avoids the rather complex bit
extraction.<br>
</div>
</blockquote>
<br>
<br>
Looks good to me. One detail in parNewGeneration.cpp:<br>
<br>
274 } else {<br>
275 // Too large; allocate the object individually.<br>
276 gc_tracer()->report_promotion_outside_plab_event(old,
word_sz, age, false);<br>
277 obj = sp->par_allocate(word_sz);<br>
278 }<br>
<br>
Seems like par_allocate() return NULL. Maybe we should check that
before reporting the event. Similarly to what you do in the other
GCs, for example G1:<br>
<br>
g1Allocator.cpp<br>
<br>
141 obj = _g1h->par_allocate_during_gc(purpose, word_sz,
context);<br>
142 if (obj != NULL<br>
143 &&
_g1h->_gc_tracer_stw->should_report_promotion_outside_plab_event())
{<br>
144 bool tenured =
_g1h->heap_region_containing_raw(obj)->is_old();<br>
145
_g1h->_gc_tracer_stw->report_promotion_outside_plab_event(old,
word_sz, <br>
146
age, tenured);<br>
147 }<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<br>
<br>
<blockquote cite="mid:545B4986.1050700@oracle.com" type="cite">
<div class="moz-cite-prefix"> <br>
Cheers,<br>
Staffan<br>
<br>
On 09/15/2014 02:06 PM, Bengt Rutisson wrote:<br>
</div>
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<br>
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>
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