On Tue, 25 Feb 2025 16:43:21 GMT, Thomas Stuefe <[email protected]> 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 five additional
> commits since the last revision:
>
> - feedback ashu
> - feedback roberto
> - final-statistics-switch
> - performance fix
> - remove test code
src/hotspot/share/compiler/compilationMemoryStatistic.cpp line 306:
> 304: if (_comp_type == compiler_c2) {
> 305: // Update C2 node count
> 306: // Careful, Compile::current() may be NULL in a short time window
> when Compile itself
The recently added `sources/TestNoNULL.java` test fails due to this occurrence
of `NULL`.
Suggestion:
// Careful, Compile::current() may be null in a short time window when
Compile itself
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/23530#discussion_r1971506973
