On Fri, 27 Oct 2023 17:29:23 GMT, Gerard Ziemski <gziem...@openjdk.org> wrote:

> I really like this feature, hope the other platforms can be done as well. (I 
> am also really looking forward to seeing how you did the "malloc" version)
> 
> I think we should set the user expectations correctly and say somewhere that 
> these mappings are only for mmaped memory, ex change:
> 
> `Memory mappings:`
> 
> to
> 
> `Memory mappings (mmaped):`
> 
> or something like that.
> 

That would be more confusing since you can see C-heap mappings as well 
(mappings the libc allocates via mmap to back its arenas). We don't have VM 
annotations for them (yet), but they do show up in that list.

> These lines look akward next to each other:
> 
> ```
> 0x000000070a400000 - 0x0000000800000000  4123000832  ---p 00000000    
> JAVAHEAP                      
> 0x00007f4e747dd000 - 0x00007f4e747e1000       16384  ---p 00000000    
> STACK(72821 "AWT-EventQueue-0") 
> 0x0000563e6decb000 - 0x0000563e6decc000        4096  r--p 00000000            
>                       
> /home/gerard/Desktop/Work/8318636/jdk/build/linux-x86_64-server-fastdebug/images/jdk/bin/java
> 0x00007f4e26000000 - 0x00007f4e26d3b000    13873152  rw-p 00001000    CDS     
>                       
> /home/gerard/Desktop/Work/8318636/jdk/build/linux-x86_64-server-fastdebug/images/jdk/lib/server/classes.jsa
> ```
> 
> in my opinion. The majority of entries either have the component or path in 
> the **info** field (except CDS). Could we print it simply as:
> 
> ```
> 0x000000070a400000 - 0x0000000800000000  4123000832  ---p 00000000    
> JAVAHEAP                      
> 0x00007f4e747dd000 - 0x00007f4e747e1000       16384  ---p 00000000    
> STACK(72821 "AWT-EventQueue-0") 
> 0x0000563e6decb000 - 0x0000563e6decc000        4096  r--p 00000000    
> /home/gerard/Desktop/Work/8318636/jdk/build/linux-x86_64-server-fastdebug/images/jdk/bin/java
> 0x00007f4e26000000 - 0x00007f4e26d3b000    13873152  rw-p 00001000    
> CDS=/home/gerard/Desktop/Work/8318636/jdk/build/linux-x86_64-server-fastdebug/images/jdk/lib/server/classes.jsa
> ```

Hmm. Yes, that looks better. I was originally worried about VMAs for files 
being folded with other ones, then you would have confusing entries like 
"STACK.. filename bla". But that can actually never happen since VMAs with 
different files (or one has ha file, one don't) are not folded. Yes, I change 
that.

> 
> I find the compact way more aesthetically pleasing and easier to read.
> 
> Next I'm going to start looking into the implementation...

Thansk!

-------------

PR Comment: https://git.openjdk.org/jdk/pull/16301#issuecomment-1783721056

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