RFR: 8344009: Improve compiler memory statistics [v2]

[Thomas Stuefe]

On Fri, 14 Feb 2025 09:34:18 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Greetings,
>> 
>> This is a rewrite of the Compiler Memory Statistic. The primary new feature is the capability to track allocations by C2 phases. This will allow for a much faster, more thorough analysis of footprint issues. 
>> 
>> Tracking Arena memory movement is not trivial since one needs to follow the ebb and flow of allocations over nested C2 phases. A phase typically allocates more than it releases, accruing new nodes and resource area. A phase can also release more than allocated when Arenas carried over from other phases go out of scope in this phase. Finally, it can have high temporary peaks that vanish before the phase ends.
>> 
>> I wanted to track that information correctly and display it clearly in a way that is easy to understand.
>> 
>> The patch implements per-phase tracking by instrumenting the `TracePhase` stack object (thanks to @rwestrel for this idea).
>> 
>> The nice thing with this technique is that it also allows for quick analysis of a suspected hot spot (eg, the inside of a loop): drop a TracePhase in there with a speaking name, and you can see the allocations inside that phase.
>> 
>> The statistic gives us two new forms of output:
>> 
>> 1) At the moment the compilation memory *peaked*, we now get a detailed breakdown of that peak usage per phase:
>> 
>> 
>> Arena Usage by Arena Type and compilation phase, at arena usage peak of 58817816:
>>     Phase                         Total        ra      node      comp      type     index   reglive  regsplit     cienv     other
>>     none                        1205512    155104    982984     33712         0         0         0         0         0     33712
>>     parse                      11685376    720016   6578728   1899064         0         0         0         0   1832888    654680
>>     optimizer                    916584         0    556416         0         0         0         0         0         0    360168
>>     escapeAnalysis              1983400         0   1276392    707008         0         0         0         0         0         0
>>     connectionGraph              720016         0         0    621832         0         0         0         0     98184         0
>>     macroEliminate               196448         0    196448         0         0         0         0         0         0         0
>>     iterGVN                      327440         0    196368    131072         0         0         0         0         0         0
>>     incrementalInline           3992816         0   3043704    62...
>
> Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:
> 
>   revert unnecessary copyright change

> > We also save a copy of the counters to a global table that contains the N most expensive compilations. That table will be printed when one uses jcmd  Compiler.memory. We also print it into the hs-err file.
> 
> This is a new tool for me, but I'd appreciate it if there was the equivalent of `PrintNMTStatistics` such that the table produced from the JCmd is also printed on shutdown.
> 
> Edit: print_final_report doesn't support verbosity, that'd be nice to have.

Let's do this in a future RFE, if anyone misses it.

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PR Comment: https://git.openjdk.org/jdk/pull/23530#issuecomment-2667638346