RFR: 6657: Add allocation pressure column to Memory and TLAB views

[Marcus Hirt]

On Tue, 14 Jan 2020 12:19:09 GMT, Marcus Hirt <hirt at openjdk.org> wrote:

>> Yep, it's already split up in a general "Memory" page and a TLAB allocations page (which is located under JVM Internals), and which is already grouped by class. The only missing part would be the "Pressure", which is basically Total Allocation (%), added by Jie's PR.
>> 
>>> It may be cool to have some kind of extension functionality such that when a page is visited, the page can augment this generic view with additional columns (e.g. to show allocation pressure by method while on the memory page).
>> 
>> Agreed. I believe this is discussed in another already existing issue. We can start a thread on the dev-list to discuss this in more detail.
> 
> Note that copyrights need to be updated.

Hi Jie!

How about hiding the count column, or even removing it? This is the event count for both of the TLAB events - it does not correspond to the number of actual objects. We could perhaps estimate the number of allocated objects (using the size of the allocated object inside tlab and the tlab size) and add that as a new column, but the event count doesn't really make sense. Now that we have the percentages, we may want to instead have the backdrop bars on them.

Also, how about hiding the average columns by default? There is a bit of information overload right now, and I think the sums may be what people will usually want. They can show the other columns if they need them.

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PR: https://git.openjdk.java.net/jmc/pull/21