Could you tell me if the Jikes RVM has any basic block profiling "tool"?
I saw that there is profiling done on branches and I was wondering if there is anything similar on basic blocks.
Eliot Moss <firstname.lastname@example.org> wrote:
Naren Sachindran, a PhD student in my lab, built card marking as part of
his Memory-Constrained Copying (MC^2) collector. But it probably won't help
you much since:
- We use cards only when remsets are too big
- All marking of cards happens by the GC; the mutator write barrier
continues to enter possibly interesting slots in write buffers, which the
- MC^2 has a marking process that identifies the reachable objects; we
use the mark bits to identify where object headers are within the range
of a card, avoiding the need to scan (or to change the object model, as
Steve B described)
With the current object model, one could maintain a bitmap indicating where
each object header is---at a relative cost of 1/32 in space, i.e., about
3%, and a time cost to locate and set the correct bit upon each
allocation. However, you may need to
do this only for older generations in
a generational system, so the vast majority of allocation would not need to
set the bits.
But I think what we're all confirming is that there is no ready-to-go,
standard, card marking infrastructure available.
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