RFR: 8273112: -Xloggc and -Xlog should override -verbose

[David Holmes]

On 1/09/2021 5:36 pm, Xiaowei Lu wrote:
> On Wed, 1 Sep 2021 02:03:48 GMT, Ioi Lam <iklam at openjdk.org> wrote:
> 
>>> According to java 16 specifications for java command (https://docs.oracle.com/en/java/javase/16/docs/specs/man/java.html), the command line option -Xloggc should override -verbose:gc if both options are given with the same java command. However, gc information still outputs to console even if gc log file is specified.
>>>
>>> $java -Xloggc:gc.log -verbose:gc -version
>>> [0.000s][warning][gc] -Xloggc is deprecated. Will use -Xlog:gc:gc.log instead.
>>> [0.003s][info ][gc] Using G1
>>> $cat gc.log
>>> [0.003s][info][gc] Using G1
>>>
>>> In addition, since -Xloggc:filename is replaced by -Xlog:gc:filename, can we assume that -Xlog:gc:filename should override -verbose:gc as -Xloggc:filename? Currently, gclog still outputs to both stdout and file if -Xlog and -verbose are given with the same java command.
>>>
>>> $java -Xlog:gc:gc.log -verbose:gc -version
>>> [0.003s][info][gc] Using G1
>>> $cat gc.log
>>> [0.003s][info][gc] Using G1
>>>
>>> As a result, we propose to put off the log configuration of -verbose option until we are confident that there isn’t -Xloggc or -Xlog options.
>>
>> src/hotspot/share/runtime/arguments.cpp line 2965:
>>
>>> 2963:     }
>>> 2964:     if (ts->contains(LogTag::_class) && ts->has_output_to_file()) {
>>> 2965:       has_verbose_class = false;
>>
>> This doesn't seem correct to me. If the command line is:
>>
>>
>> java -Xlog:class+resolve=debug:file=log.txt -verbose:class -version
>>
>>
>> We should have the following:
>>
>>
>> (a) class,load -> stdout
>> (b) class,unload -> stdout
>> (c) class,resolve -> log.txt
>>
>>
>> But your change will disable both (a) and (b).
>>
>>
>> Also, what is the proposed behavior with this?
>>
>>
>> java -Xlog:class+load:file=log.txt -verbose:class -version
>>
>>
>> Will we have [A]:
>>
>>
>> class,load -> log.txt
>> class,unload -> stdout
>>
>>
>> or [B]?
>>
>>
>> class,load -> log.txt
>> class,unload -> disabled
> 
> For your java command:
> 
> java -Xlog:class+load:file=log.txt -verbose:class -version
> 
> We will have [B] according to the current commit:
> 
> class,load -> log.txt
> class,unload -> disabled
> 
> But I'm not sure whether this behavior is correct. The website (https://docs.oracle.com/en/java/javase/16/docs/specs/man/java.html) doesn't give us explicit clue. It only says -verbose:class equals -Xlog:class+load=info,class+unload=info.
> For the command above, maybe we can propose a third way [C]:
> 
> class,load -> log.txt and stdout
> class,unload -> stdout
> 
> In addition, what if the command is:
> 
> java -Xlog:class+load=error,class+unload=info:log.txt -verbose:class -version
> 
> In this case, since ``class+load=error`` is ”weaker" than ``class+load=info``, maybe -verbose should not be overriden by -Xlog?

There is no specification that states that -verbose:X is overridden by 
-Xlog:X except for GC. For the non-GC case the -verbose:X argument 
should be  processed in its -Xlog form and the full command-line 
processed as-if only -Xlog had been used. That is very clear and simple 
to implement.

The GC case is more problematic as per my other comment. There is no 
clear definition of what override means, but I would think that "ignore" 
would be appropriate. The main problem is that you have to scan the 
entire command-line to know what to do with the -verbose:gc.

David
-----

> To make things simple, in my commit, as long as "class"  shows up, no matter it's ``-Xlog:class`` or ``-Xlog:class+resolve`` or ``-Xlog:class=debug``  , then ``-verbose:class`` is to be overiden. But I'm quite uncertain about whether it is correct. Looking forward to your suggestions.
> 
> -------------
> 
> PR: https://git.openjdk.java.net/jdk/pull/5295
>