Hi Paul, Yes, I'm reviewing it. Sorry for the late reply.
Thanks, Serguei On 8/6/20 06:49, Hohensee, Paul wrote:
And a submit repo run succeeds.
Serguei, would you be willing to review?
Thanks,
Paul
On 8/5/20, 7:00 PM, "linzang(臧琳)" <linz...@tencent.com> wrote:
CAUTION: This email originated from outside of the organization. Do not
click links or open attachments unless you can confirm the sender and know the
content is safe.
Thanks Paul!
And I have verified this change could build success in windows.
BRs,
Lin
On 2020/8/6, 4:17 AM, "Hohensee, Paul" <hohen...@amazon.com> wrote:
Two tiny nits that don't need a new webrev:
In heapInspection.cpp, you don't need to cast missed_count to uintx in
the call to log_info().
In heapInspection.hpp, you can delete two of the three blank lines
before #endif // SHARE_MEMORY_HEAPINSPECTION_HPP
Thanks,
Paul
On 8/5/20, 6:46 AM, "linzang(臧琳)" <linz...@tencent.com> wrote:
Hi Paul, Stefan and Serguei,
Here I uploaded a new changeset, would you like to help review
again?
Webrev:
http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_11/
Delta (based on webrev10):
http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_11_delta/
P.S. I am in process of building it on windows environment
for a double check. May update result later. Thanks!
BRs,
Lin
On 2020/8/5, 8:56 PM, "Hohensee, Paul" <hohen...@amazon.com> wrote:
uintx is fine with me.
Thanks,
Paul
On 8/5/20, 1:14 AM, "linzang(臧琳)" <linz...@tencent.com> wrote:
Hi Stefan,
I got your point, thanks for explanation.
I missed the atomic part when considering it.
Hi Paul,
Do you think it is ok to use uintx? I checked it is
actually a uintptr_t type.
BRs,
Lin
On 2020/8/5, 3:39 PM, "Stefan Karlsson"
<stefan.karls...@oracle.com> wrote:
On 2020-08-05 07:22, linzang(臧琳) wrote:
> Hi Serguei,
>
> No problem, Thanks for your reviewing :)
>
> I wll upload a new webrev later, so may I ask
your help to review it
> again?
>
> Hi Stefan,
>
> As Paul mentioned, the _/missed/_count is not a
size, so size_t may
> not be clear, what’s your opinion about uint64_t?
We typically don't restrict the usage of size_t to
only *sizes* in the
HotSpot. If you search the code you'll find many count
variables using
size_t, so I personally don't see the need to change
the type.
However, if you really do want to change it then maybe
using another
type that is 32 bits on 32-bit machines, maybe uintx?
IIRC, using
uint64_t and some of the Atomics operations are
problematic on some
32-bit platforms, so using a type that matches the
word size of the
targetted machine helps you not having to think about
that.
>
> It seems the uint overflow may happened on 64bit
machine with large
> heap, e.g. may be more than 4 Giga objects (8byte
header + 8 byte
> klassptr + 8byte field) in a heap that is larger
than 96 GB, uint64_t
> is ok in this case.
Exactly.
Thanks,
StefanK
>
> BRs,
>
> Lin
>
> *From: *"serguei.spit...@oracle.com"
<serguei.spit...@oracle.com>
> *Date: *Wednesday, August 5, 2020 at 1:02 PM
> *To: *"linzang(臧琳)" <linz...@tencent.com>, "Hohensee,
Paul"
> <hohen...@amazon.com>, Stefan Karlsson
<stefan.karls...@oracle.com>,
> David Holmes <david.hol...@oracle.com>,
serviceability-dev
> <serviceability-dev@openjdk.java.net>,
"hotspot-gc-...@openjdk.java.net"
> <hotspot-gc-...@openjdk.java.net>
> *Subject: *Re: RFR(L): 8215624: add parallel heap
inspection support for
> jmap histo(G1)(Internet mail)
>
> Oh, sorry for the confusion, please, skip my
question. :)
> C++ does not have the '&&=' operator.
>
> Thanks,
> Serguei
>
> On 8/4/20 21:56, serguei.spit...@oracle.com
> <mailto:serguei.spit...@oracle.com> wrote:
>
> Hi Lin,
>
>
https://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_10/src/hotspot/share/memory/heapInspection.cpp.udiff.html
>
> +class KlassInfoTableMergeClosure : public
KlassInfoClosure {
>
> +private:
>
> + KlassInfoTable* _dest;
>
> + bool _success;
>
> +public:
>
> + KlassInfoTableMergeClosure(KlassInfoTable*
table) : _dest(table),
> _success(true) {}
>
> + void do_cinfo(KlassInfoEntry* cie) {
>
> + _success &= _dest->merge_entry(cie);
>
> + }
>
> The operator '&=' above looks strange.
> Did you actually want to use the operator '&&='
instead? :
>
> + _success &&= _dest->merge_entry(cie);
>
>
> Thanks,
> Serguei
>
>
>
>
> On 8/3/20 07:51, linzang(臧琳) wrote:
>
> Dear Stefan,
>
> May I ask your help to review
again? I have made a delta based on the last changeset you have
reviewed(webrev04),hope it could ease your reviewing work.
>
>
webrev:https://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_10/
>
> delta (vs
webrev04):https://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/delta_10vs04/webrev/
>
>
bug:https://bugs.openjdk.java.net/browse/JDK-8215624
>
>
CSR(approved):https://bugs.openjdk.java.net/browse/JDK-8239290
>
>
>
> BRs,
>
> Lin
>
> On 2020/7/30, 5:21 AM, "Hohensee,
Paul"<hohen...@amazon.com> <mailto:hohen...@amazon.com> wrote:
>
> A submit repo run with this succeeded,
so afaic you're good to go. Stefan, you reviewed the GC part before, it'd be great
if you could ok the final version.
>
> Thanks,
>
> Paul
>
> On 7/29/20, 5:02 AM,
"linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
> Upload a new change
athttp://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_10/
>
> It fix an issue of windows fail :
>
> ####################################
>
> In heapInspect.cpp
>
> - size_t
HeapInspection::populate_table(KlassInfoTable* cit, BoolObjectClosure *filter,
uint parallel_thread_num) {
>
> + uint
HeapInspection::populate_table(KlassInfoTable* cit, BoolObjectClosure *filter,
uint parallel_thread_num) {
>
> ####################################
>
> In heapInspect.hpp
>
> - size_t
populate_table(KlassInfoTable* cit, BoolObjectClosure* filter = NULL, uint
parallel_thread_num = 1) NOT_SERVICES_RETURN_(0);
>
> + uint
populate_table(KlassInfoTable* cit, BoolObjectClosure* filter = NULL, uint
parallel_thread_num = 1) NOT_SERVICES_RETURN_(0);
>
> ####################################
>
> BRs,
>
> Lin
>
> On 2020/7/27, 11:26 AM,
"linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
> I update a new change
athttp://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_09
>
> It includes a tiny fix of build
failure on windows:
>
>
####################################
>
> In attachListener.cpp:
>
> - uint parallel_thread_num =
MAX(1, (uint)os::initial_active_processor_count() * 3 / 8);
>
> + uint parallel_thread_num =
MAX2<uint>(1, (uint)os::initial_active_processor_count() * 3 / 8);
>
>
####################################
>
> BRs,
>
> Lin
>
> On 2020/7/23, 11:56 AM,
"linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
> Hi Paul,
>
> Thanks for your help,
that all looks good to me.
>
> Just 2 minor changes:
>
> • delete the final
return in ParHeapInspectTask::work, you mentioned it but seems not include in the
webrev :-)
>
> • delete a
unnecessary blank line in heapInspect.cpp at merge_entry()
>
>
#########################################################################
>
> ---
old/src/hotspot/share/memory/heapInspection.cpp 2020-07-23 11:23:29.281666456
+0800
>
> +++
new/src/hotspot/share/memory/heapInspection.cpp 2020-07-23 11:23:29.017666447
+0800
>
> @@ -251,7 +251,6 @@
>
>
_size_of_instances_in_words += cie->words();
>
> return true;
>
> }
>
> -
>
> return false;
>
> }
>
> @@ -568,7 +567,6 @@
>
>
Atomic::add(&_missed_count, missed_count);
>
> } else {
>
>
Atomic::store(&_success, false);
>
> - return;
>
> }
>
> }
>
>
#########################################################################
>
> Here is the
webrevhttp://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_08/
>
> BRs,
>
> Lin
>
>
---------------------------------------------
>
> From: "Hohensee,
Paul"<hohen...@amazon.com> <mailto:hohen...@amazon.com>
>
> Date: Thursday, July 23,
2020 at 6:48 AM
>
> To: "linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com>, Stefan Karlsson<stefan.karls...@oracle.com>
<mailto:stefan.karls...@oracle.com>,"serguei.spit...@oracle.com" <mailto:serguei.spit...@oracle.com> <serguei.spit...@oracle.com>
<mailto:serguei.spit...@oracle.com>, David Holmes<david.hol...@oracle.com> <mailto:david.hol...@oracle.com>, serviceability-dev<serviceability-dev@openjdk.java.net>
<mailto:serviceability-dev@openjdk.java.net>,"hotspot-gc-...@openjdk.java.net" <mailto:hotspot-gc-...@openjdk.java.net> <hotspot-gc-...@openjdk.java.net>
<mailto:hotspot-gc-...@openjdk.java.net>
>
> Subject: RE: RFR(L):
8215624: add parallel heap inspection support for jmap histo(G1)(Internet mail)
>
> Just small things.
>
> heapInspection.cpp:
>
> In
ParHeapInspectTask::work, remove the final return statement and fix the following
‘}’ indent. I.e., replace
>
> +
Atomic::store(&_success, false);
>
> + return;
>
> + }
>
> with
>
> +
Atomic::store(&_success, false);
>
> + }
>
> In
HeapInspection::heap_inspection, missed_count should be a uint to match other
missed_count declarations, and should be initialized to the result of
populate_table() rather than separately to 0.
>
> attachListener.cpp:
>
> In heap_inspection,
initial_processor_count returns an int, so cast its result to a uint.
>
> Similarly, parse_uintx
returns a uintx, so cast its result (num) to uint when assigning to
parallel_thread_num.
>
> BasicJMapTest.java:
>
> I took the liberty of
refactoring testHisto*/histoToFile/testDump*/dump to remove redundant
interposition methods and make histoToFile and dump look as similar as possible.
>
> Webrev with the above
changes in
>
>
http://cr.openjdk.java.net/~phh/8214535/webrev.01/
>
> Thanks,
>
> Paul
>
> On 7/15/20, 2:13 AM,
"linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
> Upload a new webrev
athttp://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_07/
>
> It fix a potential issue that
unexpected number of threads maybe calculated for "parallel" option of jmap -histo
in container.
>
> As shown
athttp://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_07-delta/src/hotspot/share/services/attachListener.cpp.udiff.html
>
> ###############
attachListener.cpp ####################
>
> @@ -252,11 +252,11 @@
>
> static jint
heap_inspection(AttachOperation* op, outputStream* out) {
>
> bool
live_objects_only = true; // default is true to retain the behavior before this
change is made
>
> outputStream* os =
out; // if path not specified or path is NULL, use out
>
> fileStream* fs =
NULL;
>
> const char* arg0 =
op->arg(0);
>
> - uint
parallel_thread_num = MAX(1, os::processor_count() * 3 / 8); // default is less
than half of processors.
>
> + uint
parallel_thread_num = MAX(1, os::initial_active_processor_count() * 3 / 8); //
default is less than half of processors.
>
> if (arg0 != NULL &&
(strlen(arg0) > 0)) {
>
> if (strcmp(arg0, "-all") != 0
&& strcmp(arg0, "-live") != 0) {
>
>
out->print_cr("Invalid argument to inspectheap operation: %s", arg0);
>
> return JNI_ERR;
>
> }
>
>
###################################################
>
> Thanks.
>
> BRs,
>
> Lin
>
> On 2020/7/9, 3:22 PM,
"linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
> Hi Paul,
>
> Thanks for
reviewing!
>
> >>
>
> >> I'd move all the
argument parsing code to JMap.java and just pass the results to Hotspot. Both histo() in JMap.java
and code in attachListener.* parse the command line arguments, though the code in histo() doesn't
parse the argument to "parallel". I'd upgrade the code in histo() to do a complete parse
and pass the option values to executeCommandForPid as before: there would just be more of them
now. That would allow you to eliminate all the parsing code in attachListener.cpp as well as the
change to arguments.hpp.
>
> >>
>
> The reason I made the
change in Jmap.java that compose all arguments as 1 string , instead of passing 3 argments,
is to avoid the compatibility issue, as we discussed
inhttp://mail.openjdk.java.net/pipermail/serviceability-dev/2019-February/thread.html#27240.
The root cause of the compatibility issue is because max argument count in
HotspotVirtualMachineImpl.java and attachlistener.cpp need to be enlarged (changes
likehttp://hg.openjdk.java.net/jdk/jdk/rev/e7cf035682e3#l2.1) when jmap has more than 3
arguments. But if user use an old jcmd/jmap tool, it may stuck at socket read(), because the
"max argument count" don't match.
>
> I re-checked
this change, the argument count of jmap histo is equal to 3 (live, file,
parallel), so it can work normally even without the change of passing argument.
But I think we have to face the problem if more arguments is added in jcmd alike
tools later, not sure whether it should be sloved (or a workaround) in this
changeset.
>
> And here are
the lastest webrev and delta:
>
>
http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_06/
>
>
http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_06-delta/
>
> Cheers,
>
> Lin
>
> On 2020/7/7, 5:57 AM, "Hohensee,
Paul"<hohen...@amazon.com> <mailto:hohen...@amazon.com> wrote:
>
> I'd like to see
this feature added. :)
>
> The CSR looks
good, as does the basic parallel inspection algorithm. Stefan's done the GC part,
so I'll stick to the non-GC part (fwiw, the GC part lgtm).
>
> I'd move all the argument
parsing code to JMap.java and just pass the results to Hotspot. Both histo() in JMap.java
and code in attachListener.* parse the command line arguments, though the code in histo()
doesn't parse the argument to "parallel". I'd upgrade the code in histo() to do a
complete parse and pass the option values to executeCommandForPid as before: there would
just be more of them now. That would allow you to eliminate all the parsing code in
attachListener.cpp as well as the change to arguments.hpp.
>
>
heapInspection.hpp:
>
>
_shared_miss_count (s/b _missed_count, see below) isn't a size, so it should be a
uint instead of a size_t. Same with the new parallel_thread_num argument to
heap_inspection() and populate_table().
>
> Comment
copy-edit:
>
> +// Parallel
heap inspection task. Parallel inspection can fail due to
>
> +// a native
OOM when allocating memory for TL-KlassInfoTable.
>
> +// _success
will be set false on an OOM, and serial inspection tried.
>
>
_shared_miss_count should be _missed_count to match the missed_count() getter, or
rename missed_count() to be shared_miss_count(). Whichever way you go, the field
type should match the getter result type: uint is reasonable.
>
>
heapInspection.cpp:
>
> You might use
ResourceMark twice in populate_table, separately for the parallel attempt and the
serial code. If the parallel attempt fails and available memory is low, it would
be good to clean up the memory used by the parallel attempt before doing the
serial code.
>
> Style nit in
KlassInfoTable::merge_entry(). I'd line up the definitions of k and elt, so "k" is even with
"elt". And, because it's two lines shorter, I'd replace
>
> + } else {
>
> + return
false;
>
> + }
>
> with
>
> + return false;
>
>
KlassInfoTableMergeClosure.is_success() should be just success() (i.e., no "is_"
prefix) because it's a getter.
>
> I'd reorganize
the code in populate_table() to make it more clear, vis (I changed
_shared_missed_count to _missed_count)
>
> + if
(cit.allocation_failed()) {
>
> + // fail to
allocate memory, stop parallel mode
>
> +
Atomic::store(&_success, false);
>
> + return;
>
> + }
>
> +
RecordInstanceClosure ric(&cit, _filter);
>
> +
_poi->object_iterate(&ric, worker_id);
>
> + missed_count
= ric.missed_count();
>
> + {
>
> + MutexLocker
x(&_mutex);
>
> + merge_success =
_shared_cit->merge(&cit);
>
> + }
>
> + if
(merge_success) {
>
> +
Atomic::add(&_missed_count, missed_count);
>
> + else {
>
> +
Atomic::store(&_success, false);
>
> + }
>
> Thanks,
>
> Paul
>
> On 6/29/20, 7:20 PM,
"linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
> Dear All,
>
>
Sorry to bother again, I just want to make sure that is this change worth to be
continue to work on? If decision is made to not. I think I can drop this work and
stop asking for help reviewing...
>
>
Thanks for all your help about reviewing this previously.
>
> BRs,
>
> Lin
>
> On 2020/5/9, 3:47 PM,
"linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
> Dear
All,
>
>
May I ask your help again for review the latest change? Thanks!
>
> BRs,
>
> Lin
>
> On 2020/4/28, 1:54 PM,
"linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
> Hi
Stefan,
>
>
>> - Adding Atomic::load/store.
>
>
>> - Removing the time measurement in the run_task. I renamed G1's function
>
>
>> to run_task_timed. If we need this outside of G1, we can rethink the API
>
>
>> at that point.
>
>
>> - ZGC style cleanups
>
>
Thanks for revising the patch, they are all good to me, and I have made a tiny
change based on it:
>
>
http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_04/
>
>
http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_04-delta/
>
>
it reduce the scope of mutex in ParHeapInspectTask, and delete unnecessary
comments.
>
> BRs,
>
> Lin
>
> On 2020/4/27, 4:34 PM,
"Stefan Karlsson"<stefan.karls...@oracle.com> <mailto:stefan.karls...@oracle.com>
wrote:
>
>
Hi Lin,
>
>
On 2020-04-26 05:10, linzang(臧琳) wrote:
>
>
> Hi Stefan and Paul，
>
>
> I have made a new patch based on your comments and Stefan's Poc code:
>
>
> Webrev:http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_03/
>
>
> Delta(based on Stefan's change:)
:http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_03-delta/webrev_03-delta/
>
>
Thanks for providing a delta patch. It makes it much easier to look at,
>
>
and more likely for reviewers to continue reviewing.
>
>
I'm going to continue focusing on the GC parts, and leave the rest to
>
>
others to review.
>
>
>
>
>
> And Here are main changed I made and want to discuss with you:
>
> > 1.
changed"parallelThreadNum=" to "parallel=" for jmap -histo options.
>
>
> 2. Add logic to test where parallelHeapInspection is fail, in
heapInspection.cpp
>
>
> This is because the parHeapInspectTask create thread local
KlassInfoTable in it's work() method, and this may fail because of native OOM, in
this case, the parallel should fail and serial heap inspection can be tried.
>
> > One more thing I
want discuss with you is about the member "_success" of parHeapInspectTask, when native OOM happenes, it
is set to false. And since this "set" operation can be conducted in multiple threads, should it be atomic
ops? IMO, this is not necessary because "_success" can only be set to false, and there is no way to
change it from back to true after the ParHeapInspectTask instance is created, so it is save to be non-atomic, do
you agree with that?
>
>
In these situations you should be using the Atomic::load/store
>
>
primitives. We're moving toward a later C++ standard were data races are
>
>
considered undefined behavior.
>
> > 3.
make CollectedHeap::run_task() be an abstract virtual func, so that every subclass of
collectedHeap should support it, so later implementation of new collectedHeap will not miss the
"parallel" features.
>
> >
The problem I want to discuss with you is about epsilonHeap and SerialHeap, as
they may not need parallel heap iteration, so I only make task->work(0), in case the
run_task() is invoked someway in future. Another way is to left run_task()
unimplemented, which one do you think is better?
>
>
I don't have a strong opinion about this.
>
>
And also please help take a look at the zHeap, as there is a class
>
>
zTask that wrap the abstractGangTask, and the collectedHeap::run_task()
>
>
only accept AbstraceGangTask* as argument, so I made a delegate class
>
>
to adapt it , please see src/hotspot/share/gc/z/zHeap.cpp.
>
>
>
>
>
> There maybe other better ways to sovle the above problems, welcome for
any comments, Thanks!
>
>
I've created a few cleanups and changes on top of your latest patch:
>
>
https://cr.openjdk.java.net/~stefank/8215624/webrev.02.delta
>
>
https://cr.openjdk.java.net/~stefank/8215624/webrev.02
>
>
- Adding Atomic::load/store.
>
>
- Removing the time measurement in the run_task. I renamed G1's function
>
>
to run_task_timed. If we need this outside of G1, we can rethink the API
>
>
at that point.
>
>
- ZGC style cleanups
>
>
Thanks,
>
>
StefanK
>
>
>
>
>
> BRs,
>
>
> Lin
>
>
>
>
> > On 2020/4/23, 11:08
AM, "linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com> wrote:
>
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Thanks Paul! I agree with using "parallel", will make the update in next patch,
Thanks for help update the CSR.
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> BRs,
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> Lin
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> > On 2020/4/23,
4:42 AM, "Hohensee, Paul"<hohen...@amazon.com> <mailto:hohen...@amazon.com> wrote:
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> > For the interface,
I'd use "parallel" instead of "parallelThreadNum". All the other options are lower case, and
it's a lot easier to type "parallel". I took the liberty of updating the CSR. If you're ok with it, you
might want to change variable names and such, plus of course JMap.usage.
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> Thanks,
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> Paul
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> >
On 4/22/20, 2:29 AM, "serviceability-dev on behalf of
linzang(臧琳)"<serviceability-dev-boun...@openjdk.java.net on behalf of
> linz...@tencent.com>
<mailto:serviceability-dev-boun...@openjdk.java.netonbehalfoflinz...@tencent.com>
wrote:
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> Dear Stefan,
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> Thanks a lot! I agree with you to decouple the heap
inspection code with GC's.
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> I will start from your POC code, may discuss with you
later.
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> BRs,
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> Lin
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> > On
2020/4/22, 5:14 PM, "Stefan Karlsson"<stefan.karls...@oracle.com>
<mailto:stefan.karls...@oracle.com> wrote:
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> Hi Lin,
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> I took a look at this earlier and saw that the heap inspection
code is
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> strongly coupled with the CollectedHeap and G1CollectedHeap.
I'd prefer
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if we'd abstract this away, so that the GCs only provide a "parallel
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object iteration" interface, and the heap inspection code is kept
elsewhere.
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> I started experimenting with doing that, but other
higher-priority (to
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> me) tasks have had to take precedence.
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> I've uploaded my work-in-progress / proof-of-concept:
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>https://cr.openjdk.java.net/~stefank/8215624/webrev.01.delta/
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>https://cr.openjdk.java.net/~stefank/8215624/webrev.01/
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> The current code doesn't handle the lifecycle (deletion) of the
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> ParallelObjectIterators. There's also code left unimplemented
in around
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> CollectedHeap::run_task. However, I think this could work as a
basis to
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> pull out the heap inspection code out of the GCs.
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> Thanks,
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> StefanK
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> On 2020-04-22 02:21, linzang(臧琳) wrote:
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> Dear all,
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> May I ask you help to review? This RFR has been there for
quite a while.
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> Thanks!
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> BRs,
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> Lin
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> > > >
On 2020/3/16, 5:18 PM, "linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com>
wrote:>
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>> Just update a new path, my preliminary measure show about 3.5x
speedup of jmap histo on a nearly full 4GB G1 heap (8-core platform with parallel thread
number set to 4).
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>>
webrev:http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_02/
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>> bug:https://bugs.openjdk.java.net/browse/JDK-8215624
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>> CSR:https://bugs.openjdk.java.net/browse/JDK-8239290
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> �� >
>> BRs,
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> >
>> Lin
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> > >>
> On 2020/3/2, 9:56 PM, "linzang(臧琳)"<linz...@tencent.com> <mailto:linz...@tencent.com>
wrote:
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>> >
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>> > Dear all,
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>> > Let me try to ease the reviewing work by some
explanation :P
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>> > The patch's target is to speed up jmap -histo for heap
iteration, from my experience it is necessary for large heap investigation. E.g in bigData
scenario I have tried to conduct jmap -histo against 180GB heap, it does take quite a while.
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>> > And if my understanding is corrent, even the jmap -histo without
"live" option does heap inspection with heap lock acquired. so it is very likely to block
mutator thread in allocation-sensitive scenario. I would say the faster the heap inspection does, the
shorter the mutator be blocked. This is parallel iteration for jmap is necessary.
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>> > I think the parallel heap inspection should be applied
to all kind of heap. However, consider the heap layout are different for GCs, much time is
required to understand all kinds of the heap layout to make the whole change. IMO, It is not
wise to have a huge patch for the whole solution at once, and it is even harder to review it.
So I plan to implement it incrementally, the first patch (this one) is going to confirm the
implemention detail of how jmap accept the new option, passes it to attachListener of the jvm
process and then how to make the parallel inspection closure be generic enough to make it easy
to extend to different heap layout. And also how to implement the heap inspection in specific
gc's heap. This patch use G1's heap as the begining.
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>> > This patch actually do several things:
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>> > 1. Add an option "parallelThreadNum=<N>" to jmap -histo, the
default behavior is to set N to 0, means let's JVM decide how many threads to use for heap inspection. Set
this option to 1 will disable parallel heap inspection. (more details in
CSR:https://bugs.openjdk.java.net/browse/JDK-8239290)
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>> > 2. Make a change in how Jmap passing arguments, changes
inhttp://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_01/src/jdk.jcmd/share/classes/sun/tools/jmap/JMap.java.udiff.html,
originally it pass options as separate arguments to attachListener, this patch change to that
all options be compose to a single string. So the arg_count_max in attachListener.hpp do not
need to be changed, and hence avoid the compatibility issue, as disscussed
athttps://mail.openjdk.java.net/pipermail/serviceability-dev/2019-March/027334.html
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>> > 3. Add an abstract class ParHeapInspectTask in
heapInspection.hpp / heapInspection.cpp, It's work(uint worker_id) method prepares the data
structure (KlassInfoTable) need for every parallel worker thread, and then call
do_object_iterate_parallel() which is heap specific implementation. I also added some
machenism in KlassInfoTable to support parallel iteration, such as merge().
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>> > 4. In specific heap (G1 in this patch), create a subclass
of ParHeapInspectTask, implement the do_object_iterate_parallel() for parallel heap
inspection. For G1, it simply invoke g1CollectedHeap's object_iterate_parallel().
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>> > 5. Add related test.
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>> > 6. it may be easy to extend this patch for other kinds of
heap by creating subclass of ParHeapInspectTask and implement the do_object_iterate_parallel().
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>> >
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>> > Hope these info could help on code review and initate the
discussion :-)
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>> > Thanks!
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>> >
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>> > BRs,
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> >
>> > Lin
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> > >>
> >On 2020/2/19, 9:40 AM, "linzang(臧琳)"<linz...@tencent.com>
<mailto:linz...@tencent.com> wrote:.
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>> > >
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>> > > Re-post this RFR with correct enhancement number to make it
trackable.
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>> > > please ignore the previous wrong post. sorry for troubles.
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>> > >
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>> > >
webrev:http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_01/
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>> > > Hi bug:https://bugs.openjdk.java.net/browse/JDK-8215624
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>> > > CSR:https://bugs.openjdk.java.net/browse/JDK-8239290
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> >
>> > > --------------
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>> > > Lin
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>> > > >Hi Lin,
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> >
> > > > >
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>> > > >Could you, please, re-post your RFR with the right
enhancement number in
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>> > > >the message subject?
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>> > > >It will be more trackable this way.
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>> > > >
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>> > > >Thanks,
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>> > > >Serguei
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>> > > >
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>> > > >
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>> > > >On 2/17/20 10:29 PM, linzang(臧琳) wrote:
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>> > > >> Dear David,
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>> > > >> Thanks a lot!
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>> > > >> I have updated the refined code
tohttp://cr.openjdk.java.net/~lzang/jmap-8214535/8215264/webrev_01/.
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>> > > >> IMHO the parallel heap inspection can be extended to
all kinds of heap as long as the heap layout can support parallel iteration.
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>> > > >> Maybe we can firstly use this webrev to discuss how to
implement it, because I am not sure my current implementation is an appropriate way to communicate with
collectedHeap, then we can extend the solution to other kinds of heap.
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>> > > >>
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>> > > >> Thanks,
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> >
>> > > >> --------------
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>> > > >> Lin
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> >
>> > > >>> Hi Lin,
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> >
>> > > >>>
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>> > > >>> Adding in hotspot-gc-dev as they need to see how this
interacts with GC
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>> > > >>> worker threads, and whether it needs to be extended beyond G1.
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>> > > >>>
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>> > > >>> I happened to spot one nit when browsing:
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>> > > >>>
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>> > > >>> src/hotspot/share/gc/shared/collectedHeap.hpp
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>> > > >>>
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>> > > >>> + virtual bool run_par_heap_inspect_task(KlassInfoTable* cit,
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>> > > >>> + BoolObjectClosure*
filter,
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>> > > >>> + size_t*
missed_count,
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>> > > >>> + size_t thread_num) {
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>> > > >>> + return NULL;
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>> > > >>>
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>> > > >>> s/NULL/false/
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>> > > >>>
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>> > > >>> Cheers,
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>> > > >>> David
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> >
> > > > >>>
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> >
>> > > >>> On 18/02/2020 2:15 pm, linzang(臧琳) wrote:
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>> > > >>>> Dear All,
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>> > > >>>> May I ask your help to review the follow changes:
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>> > > >>>> webrev:
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>> > >
>>>>http://cr.openjdk.java.net/~lzang/jmap-8214535/8215264/webrev_00/
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>> > > >>>> bug:https://bugs.openjdk.java.net/browse/JDK-8215624
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>> > > >>>> related
CSR:https://bugs.openjdk.java.net/browse/JDK-8239290
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>> > > >>>> This patch enable parallel heap inspection of G1 for
jmap histo.
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>> > > >>>> my simple test shown it can speed up 2x of jmap
-histo with
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>> > > >>>> parallelThreadNum set to 2 for heap at ~500M on 4-core
platform.
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>> > > >>>>
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>> > > >>>>
------------------------------------------------------------------------
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>> > > >>>> BRs,
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>> > > >>>> Lin
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>> > > >> >
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