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 03:04:38 UTC 2020


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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