VMPI_alloca pointer scan should only consider used portion; pointerfree alloca memory might be desirable

NEW
Unassigned

Status

Tamarin
Garbage Collection (mmGC)
P4
normal
9 years ago
7 years ago

People

(Reporter: Tommy Reilly, Unassigned)

Tracking

unspecified
Q1 12 - Brannan
Bug Flags:
flashplayer-qrb ?

Details

(Reporter)

Description

9 years ago
The GC scans the entire RCRootSegment regardless of stackTop.   I'm not familiar with its usage enough to know if this is a real problem but in theory we only need to scan to stackTop and there could be unnecessary retention caused by scanning everything.

Another concern is that most VMPI_alloca callers are allocating pointer free memory (chars/wchar/ints) but we always scan this memory.  Maybe VMPI_alloca should have a separate path for opaque memory that doesn't use GCRoots.

If AVMPLUS_HEAP_ALLOCA is defined these problems become more prevalent since we stop using the C stack completely.
(Reporter)

Updated

9 years ago
Priority: -- → P3
Target Milestone: --- → Future

Updated

8 years ago
Target Milestone: Future → flash10.2

Comment 1

8 years ago
Really two different bugs here.
Summary: VMPI_alloca is suboptimal from a GC perspective → VMPI_alloca pointer scan should only consider used portion; pointerfree alloca memory might be desirable

Updated

8 years ago
Priority: P3 → --
Target Milestone: flash10.2 → Future

Updated

8 years ago
See Also: → bug 596556

Comment 2

8 years ago
With the new StackMemory type we can now handle the stack top appropriately.

Regarding the other problem, most VMPI_alloca callers are, so far as I can tell, *not* allocating pointer-free memory -- I looked into that a couple of weeks ago, and apart from code in the number<->string code, all memory allocated appeared to be for argument areas for method invocation, this also appeared to be the case in the Flash Player.
Priority: -- → P3
Target Milestone: Future → Q3 11 - Serrano

Updated

7 years ago
Priority: P3 → P4

Updated

7 years ago
Target Milestone: Q3 11 - Serrano → Q1 12 - Brannan

Updated

7 years ago
Flags: flashplayer-qrb?
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