[prev in list] [next in list] [prev in thread] [next in thread] 

List:       openjdk-serviceability-dev
Subject:    RE: RFR(L) 8227745: Enable Escape Analysis for Better Performance in the Presence of JVMTI Agents
From:       "Lindenmaier, Goetz" <goetz.lindenmaier () sap ! com>
Date:       2020-07-23 14:19:57
Message-ID: AM4PR0202MB296490252335D6D6D638277AEC760 () AM4PR0202MB2964 ! eurprd02 ! prod ! outlook ! com
[Download RAW message or body]

Hi Richard, 

Thanks for your two further explanations in the other thread. 
That made the points clear to me.

> > I was not that happy with the names saying not_global_escape
> > and similar. I now agreed you have to use the terms of the escape
> > analysis (NoEscape ArgEscape= throughout the runtime code. I'm still not happy with
> > the 'not' in the term, I always try to expand the name to some
> > sentence with a negated verb, but it makes no sense.
> > For example, "has_not_global_escape_in_scope" expands to
> > "Hasn't a global escape in its scope." in my thinking, which makes
> > no sense. You probably mean
> > "Has not-global escape in its scope." or "Has {ArgEscape|NoEscape}
> > in its scope."
> 
> > C2 is using the word "non" in this context, e.g., here
> > alloc->is_non_escaping.
> 
> There is also ConnectionGraph::not_global_escape()
That talks about a single node that represents a single 
Object. An object has a single state wrt. ea.
You use the term for safepoint which tracks a set of objects.
Here, has_not_global_excape can mean
  1. None of the several objects does escape globaly.
  2. There is at least one object that escapes globaly.

> > non obviously negates the adjective 'global',
> > non-global or nonglobal even is a English term I find in the
> > net.
> > So what about "has_non_global_escape_in_scope?"
> 
> And what about has_ea_local_in_scope?
That's good. Please document somewhere that 
Ea_local == ArgEscape | NoEscape.
That's what it is, right?

> > Does jvmti specify that the same limits are used ...?
> > ok on your side.
> 
> I don't know and didn't find anything in a quick search.
Ok, not your business.

> 
> > jvmtiEnvBase.cpp  ok
> > jvmtiImpl.h|cpp  ok
> > jvmtiTagMap.cpp ok
> > whitebox.cpp ok
> 
> > deoptimization.cpp
> 
> > line 177: Please break line
> > line 246, 281: Please break line
> > 1578, 1583, 1589, 1632, 1649, 1651 Break line
> 
> > 1651: You use 'non'-terms, too: non-escaping :)
> 
> I know :) At least here it is wrong I'd say. "...has to be a not escaping obj..."
> sounds better
> (hopefully not only to my german ears).
I thought the term non-escpaing makes it quite clear.
I just wanted to point out that using non above would
be similar to the wording here.

> > IterateHeapWithEscapeAnalysisEnabled.java
> 
> > line 415:
> > msg("wait until target thread has set testMethod_result");
> > while (testMethod_result == 0) {
> >     Thread.sleep(50);
> > }
> > Might the test run into timeouts at this place?
> > The field is volatile, i.e. it will be reloaded
> > in each iteration. But will dontinline_testMethod
> > write it back to main memory in time?
> 
> You mean, the test could hang in that loop for a couple of minutes? I don't
> think so. There are cache coherence protocols in place which will invalidate
> stale data very timely.
Ok, anyways, it would only be a hanging test.
> 
> Ok. I've removed quite a lot of the occurrances.
> 
> > Also, I like full sentences in comments.
> > Especially for me as foreign speaker, this makes
> > things much more clear. I.e., I try to make it
> > a real sentence with articles, capitalized and a
> > dot at the end if there is a subject and a verb
> > in first place.
> > E.g., jvmtiEnvBase.cpp:1327
> 
> Are you referring to the following?
> (from
> http://cr.openjdk.java.net/~rrich/webrevs/2019/8227745/webrev.6/src/hots
> pot/share/prims/jvmtiEnvBase.cpp.frames.html)
> 
> 1326
> 1327   // If the frame is a compiled one, need to deoptimize it.
> 1328   if (vf->is_compiled_frame()) {
> 
> This line 1327 is preexisting.
Sorry, wrong line number again. 
I think I meant
1333 // eagerly reallocate scalar replaced objects.

But I must admit, the subject is missing. It's one of these 
imperative sentences where the subject is left out, which 
are used throughout documentation.
Bad example, but still a correct sentence, so qualifies 
for punctuation?

Best regards,
  Goetz.




[prev in list] [next in list] [prev in thread] [next in thread]