RFR(S) 8233826 Change CDS dumping tty->print_cr() to unified logging

[Ioi Lam]

On 12/18/19 7:49 AM, Jiangli Zhou wrote:
> The default dumping output provides useful information, particularly
> with static archiving.
Hi Jiangli,

Thanks for looking this patch.

This patch affects only "informational" messages. It doesn't affect the 
warning/error messages, which I think are the ones that users want to see.

I agree that the informational messages are useful for developers of CDS 
(I look at them all the time). However, I don't know if any of the 
following messages would be useful to a user of CDS. These messages are 
not printed during dynamic dumping, and no one has complained.


$ java -Xshare:dump
Allocated shared space: 3221225472 bytes at 0x0000000800000000
Loading classes to share ...
Loading classes to share: done.
Reading extra data: done.
Rewriting and linking classes ...
Rewriting and linking classes: done
Number of classes 1258
     instance classes   =  1192
     obj array classes  =    58
     type array classes =     8
Updating ConstMethods ... done.
Removing unshareable information ... done.
Scanning all metaspace objects ...
Allocating RW objects ...
Allocating RO objects ...
Relocating embedded pointers ...
Relocating external roots ...
Dumping symbol table ...
Dumping objects to closed archive heap region ...
Dumping objects to open archive heap region ...
Relocating SystemDictionary::_well_known_klasses[] ...
Removing java_mirror ... done.
mc  space:      8728 [  0.1% of total] out of     12288 bytes [ 71.0% 
used] at 0x0000000800000000
rw  space:   4089896 [ 32.2% of total] out of   4091904 bytes [100.0% 
used] at 0x0000000800003000
ro  space:   7546512 [ 59.4% of total] out of   7548928 bytes [100.0% 
used] at 0x00000008003ea000
md  space:      2272 [  0.0% of total] out of      4096 bytes [ 55.5% 
used] at 0x0000000800b1d000
bm  space:    184320 [  1.5% of total] out of    184320 bytes [100.0% 
used] at 0x0000000000000000
ca0 space:    520192 [  4.1% of total] out of    520192 bytes [100.0% 
used] at 0x00000007bfc00000
oa0 space:    339968 [  2.7% of total] out of    339968 bytes [100.0% 
used] at 0x00000007bf800000
total    :  12689192 [100.0% of total] out of  12701696 bytes [ 99.9% used]



> Developers may not know which logging option
> needs to be specified to enable the output.
>
> One possible solution is to enable -Xlog:cds by default for
> -Xshare:dump, if the output method is converted to use unified
> logging.

I suppose if someone is interested, they can find out the tag 
information by reading the documentation? That's the same if you want to 
see the logs for other VM features such as gc or class loading.

Thanks
- Ioi

>
> Regards,
> Jiangli
>
> On Tue, Dec 17, 2019 at 10:34 PM Ioi Lam <ioi.lam at oracle.com> wrote:
>> https://bugs.openjdk.java.net/browse/JDK-8233826
>> http://cr.openjdk.java.net/~iklam/jdk15/8233826-cds-change-tty-to-ul.v01/
>>
>> During CDS dumping, a few messages are printed out unconditionally
>> using tty->print_cr(). This patch changes the message to use
>> log_info(cds) instead.
>>
>> Some test cases were expecting the messages in stdout. I modified
>> these tests to explicitly pass -Xlog:cds.
>>
>> Thanks
>> - Ioi
>>