RFR(L): 8215624: add parallel heap inspection support for jmap histo(G1)(Internet mail)

serguei.spitsyn at oracle.com serguei.spitsyn at oracle.com
Tue Aug 11 06:40:07 UTC 2020


Hi Lin,

I prefer a conservative approach and do not change things without a real 
need.

Thanks,
Serguei

On 8/10/20 20:23, linzang(臧琳) wrote:
> Hi Serguei
>      I got your point, just thought usage may be a little verbosity, it prints almost my whole screen which could flush the error message. And I checked that other jcmd tools usually use System.exit() after print errors. So I made the change.
>
> Thanks!
> Lin
>
>> On Aug 11, 2020, at 11:05 AM, "serguei.spitsyn at oracle.com" <serguei.spitsyn at oracle.com> wrote:
>>
>> Hi Lin,
>>
>> I've re-reviewed the JMap.java only.
>> It looks good except there was no need to replace the usage(1) call with the System.exit(1).
>> I did not say usage is not needed, just that it is not enough.
>>
>> Thanks,
>> Serguei
>>
>>
>>> On 8/10/20 19:25, linzang(臧琳) wrote:
>>> Hi Serguei,
>>>           >> First, the CSR does not include any update for 'live' and 'all' options, does it?
>>>     >> If so, then I'm confused why do you need all these changes related to these two options.
>>>     >> Did you intend to really change anything?
>>>      Yes, you’re correct, CSR doesn’t mention any thing about “live” and “all”. so all those changes related become unnecessary.
>>>
>>>      Webrev: http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_13
>>>      Delta: http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_13_delta
>>>
>>>      BTW, during refining this changeset I also found an issue that jmap -dump could accept undefined options, will setup a new issue in JBS and fix it separately soon.
>>>
>>>
>>> BRs,
>>> Lin
>>>
>>> From: "serguei.spitsyn at oracle.com" <serguei.spitsyn at oracle.com>
>>> Date: Tuesday, August 11, 2020 at 8:40 AM
>>> To: "linzang(臧琳)" <linzang at tencent.com>, "Hohensee, Paul" <hohensee at amazon.com>, Stefan Karlsson <stefan.karlsson at oracle.com>, David Holmes <david.holmes at oracle.com>, serviceability-dev <serviceability-dev at openjdk.java.net>, "hotspot-gc-dev at openjdk.java.net" <hotspot-gc-dev at openjdk.java.net>
>>> Subject: Re: RFR(L): 8215624: add parallel heap inspection support for jmap histo(G1)(Internet mail)
>>>
>>> Hi Lin,
>>>
>>> A couple of things.
>>>
>>> First, the CSR does not include any update for 'live' and 'all' options, does it?
>>> If so, then I'm confused why do you need all these changes related to these two options.
>>> Did you intend to really change anything?
>>>
>>> Second, new error messages do not look useful as they say nothing about what is wrong.
>>> Printing usage does not help either.
>>> Could these messages be more specific?
>>> My suggestions are:
>>>   188                 if (filename == null) {
>>>   189                     System.err.println("Fail at processing option '" + subopt +"'");
>>>   190                     usage(1); // invalid options or no filename
>>>   191                 }
>>>    System.err.println("Fail: invalid option or no file name: '" + subopt +"'");
>>>   194                if (parallel == null) {
>>>   195                     System.err.println("Fail at processing option '" + subopt + "'");
>>>   196                     usage(1);
>>>   197                }
>>>    System.err.println("Fail: no number provided in option: '" + subopt +"'");
>>>   198             } else {
>>>   199                 System.err.println("Fail at processing option '" + subopt + "'");
>>>   200                 usage(1);
>>>   201             }
>>>    System.err.println("Fail: invalid option: '" + subopt +"'");
>>>
>>>
>>> The default value is listed in the 'parallel' flag description:
>>>    parallel=<count> generate histogram using this many parallel threads, default 0
>>> It means that the flag is optionl.
>>>
>>> I'm okay to file a separate enhancement to add a clarification for 'live' and 'all' flags.
>>>
>>> Thanks,
>>> Serguei
>>>
>>>
>>> On 8/10/20 16:46, linzang(臧琳) wrote:
>>> And Here is the latest refined changeset
>>> Webrev: http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_12/
>>> Delta: http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_12_delta/
>>>
>>> BRs,
>>> Lin
>>>
>>> On 2020/8/11, 7:23 AM, "linzang(臧琳)" mailto:linzang at tencent.com wrote:
>>>
>>>      Dear Serguei,
>>>                Here is my reply for your question about non-numeric value for “parallel” (somehow the thread of replay became out of order, not sure why).
>>>
>>>      >      >> What is going to happen if the resulting 'parallel' substring above is not a number?
>>>      >      The error handling logic locates at http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_11/src/hotspot/share/services/attachListener.cpp.frames.html, (line 276-284)
>>>      >      Generally, the result is error message will be print if “parallel” is illegal.  An example output would be:
>>>      >     ############################
>>>      >          $ time jmap -histo:parallel=c 26233
>>>      >        Exception in thread "main" com.sun.tools.attach.AttachOperationFailedException: Invalid parallel thread number: [c]
>>>      >                                              at jdk.attach/sun.tools.attach.VirtualMachineImpl.execute(VirtualMachineImpl.java:227)
>>>      >                                               at jdk.attach/sun.tools.attach.HotSpotVirtualMachine.executeCommand(HotSpotVirtualMachine.java:309)
>>>      >                                               at jdk.jcmd/sun.tools.jmap.JMap.executeCommandForPid(JMap.java:133)
>>>      >                                                at jdk.jcmd/sun.tools.jmap.JMap.histo(JMap.java:206)
>>>      >                                               at jdk.jcmd/sun.tools.jmap.JMap.main(JMap.java:112)
>>>      >
>>>      >    ############################
>>>      >
>>>      > Hi Serguei, Paul and Stefan.
>>>      >      Moreover, I will made a new changeset with following changes:
>>>      >    * Print error message + usage when parameter check fail in Jmap.java
>>>      >    *Retrive the histo logic that if “all” and “live” are set at same time, use “live”, rather than print error message. (not sure which one is better :P)
>>>
>>>      My last point is to retrive the behavior for compatibility.  And do you think make a separate enhancement about spec is reasonable ?
>>>
>>>      Thanks!
>>>
>>>      BRs,
>>>      Lin
>>>
>>>      From: mailto:serguei.spitsyn at oracle.com mailto:serguei.spitsyn at oracle.com
>>>      Date: Tuesday, August 11, 2020 at 5:11 AM
>>>      To: "linzang(臧琳)" mailto:linzang at tencent.com, "Hohensee, Paul" mailto:hohensee at amazon.com, Stefan Karlsson mailto:stefan.karlsson at oracle.com, David Holmes mailto:david.holmes at oracle.com, serviceability-dev mailto:serviceability-dev at openjdk.java.net, mailto:hotspot-gc-dev at openjdk.java.net mailto:hotspot-gc-dev at openjdk.java.net
>>>      Subject: Re: RFR(L): 8215624: add parallel heap inspection support for jmap histo(G1)(Internet mail)
>>>
>>>      Hi Lin,
>>>
>>>
>>>      On 8/7/20 03:41, linzang(臧琳) wrote:
>>>      Dear Serguei,
>>>               Thanks a lot for your review!
>>>      >> The spec says nothing if the new option 'parallel' is mandatory or optional.
>>>      >> Also, (it was before your fix) the spec does not say if the options 'live' and 'all' are mutually exclusive.
>>>               For “parallel”,  the spec adds “parallel=0” is the default behavior. So my assumption is if parallel is not used, it will be 0.  Do you think it is ok ? is it necessary to obviously add comments like “if no parallel is set, use the default value 0”?
>>>
>>>      It'd be nice to make it clear.
>>>      But the CSR will need to be updated.
>>>      In fact, I did not want you to go through this cycle again.
>>>      But maybe it is worth to improve the specs in this regard.
>>>      May be Paul has some alternative suggestions.
>>>
>>>
>>>               For “live” and “all”, before the changeset , I see the logic from the code is that both of them can be set at the same time, and the “live” will take effect. IMHO this may be a little confused. So I made the change, not sure whether I should keep the same behavior as before in this change?
>>>
>>>      This is better to clearly specify what is allowed and what is the behavior.
>>>
>>>
>>>               And I like your idea of printing more error msg if something wrong with the options setting, but I checked that before the change, if there is not a match option, it only print usage. and not only jmap -histo but also jmap -dump has this issue, do you agree if I fix both in the changeset?
>>>
>>>      Yes, it'd be nice to make it clear in both specs.
>>>
>>>                      >> What is going to happen if null is passed in place of parallel here? :
>>>              The default value 0 will be used if no “parallel” option is set.
>>>
>>>      Okay, thanks.
>>>
>>>
>>>                                     >>  Should the lines 193-195 be moved after the line 202?
>>>               I don’t think so, the logic is a little different.  At line 193, the case is “parallel=<blank>”.   If move them to line 203, it mean “parallel” is not optional.
>>>      Okay, I see what you mean.
>>>      The problem is that the help/spec says nothing about the flag 'parallel' as being optional.
>>>
>>>
>>>      I also asked this question:
>>>        Q: What is going to happen if the resulting 'parallel' sub-string above is not a number?
>>>
>>>
>>>      Thanks,
>>>      Serguei
>>>
>>>
>>>
>>>              Thanks!
>>>
>>>
>>>      BRs,
>>>      Lin
>>>
>>>      From: mailto:serguei.spitsyn at oracle.com mailto:serguei.spitsyn at oracle.com
>>>      Date: Friday, August 7, 2020 at 3:28 PM
>>>      To: "linzang(臧琳)mailto:linzang at tencent.com,Hohensee, Paulmailto:hohensee at amazon.com,StefanKarlssonmailto:stefan.karlsson at oracle.com,DavidHolmesmailto:david.holmes at oracle.com,serviceability-devmailto:serviceability-dev at openjdk.java.net,mailto:hotspot-gc-dev at openjdk.java.netmailto:hotspot-gc-dev at openjdk.java.netSubject:Re:RFR(L):8215624:addparallelheapinspectionsupportforjmaphisto(G1)(Internetmail)HiLin,Notsure,Ifullyunderstandthespecupdateandtheoptionsprocessinginthefile:http://cr.openjdk.java.net/~lzang/jmap-8214535/8215624/webrev_11/src/jdk.jcmd/share/classes/sun/tools/jmap/JMap.java.frames.htmlThespecsaysnothingifthenewoption'parallel'ismandatoryoroptional.Also,(itwasbeforeyourfix)thespecdoesnotsayiftheoptions'live'and'all'aremutuallyexclusive.TheJMap.javaimplementationjustprintusageintwocases:191}elseif(subopt.startsWith(parallel=")) {
>>>       192                parallel = subopt.substring("parallel=".length());
>>>       193                if (parallel == null) {
>>>       194                     usage(1);
>>>       195                }
>>>       ...
>>>       200         if (set_live && set_all) {
>>>       201             usage(1);
>>>       202         }
>>>      It is not that helpful as the usage does not explain anything about these corner cases.
>>>      Also, it allows to pass no parallel option.
>>>      What is going to happen if null is passed in place of parallel here? :
>>>       206         executeCommandForPid(pid, "inspectheap", liveopt, filename, parallel);
>>>
>>>      Should the lines 193-195 be moved after the line 202?
>>>
>>>      Thanks,
>>>      Serguei
>>>
>>>
>>>      On 8/5/20 18:59, linzang(臧琳) wrote:
>>>      Thanks Paul!
>>>      And I have verified this change could build success in windows.
>>>
>>>      BRs,
>>>      Lin
>>>
>>>      On 2020/8/6, 4:17 AM, "Hohensee, Paulmailto:hohensee at amazon.comwrote:Twotinynitsthatdon'tneedanewwebrev:InheapInspection.cpp,youdon'tneedtocastmissed_counttouintxinthecalltolog_info().InheapInspection.hpp,youcandeletetwoofthethreeblanklinesbefore#endif//SHARE_MEMORY_HEAPINSPECTION_HPPThanks,PaulOn8/5/20,6:46AM,linzang(臧琳)" mailto:linzang at 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
>>>
>>>
>>>
>>>
>>>
>>



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