[project @ 2001-11-08 12:46:31 by simonmar]
Fix the large block allocation bug (Yay!)
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In order to do this, I had to
1. in each heap-check failure branch, return the amount of heap
actually requested, in a known location (I added another slot
in StgRegTable called HpAlloc for this purpose). This is
useful for other reasons - in particular it makes it possible
to get accurate allocation statistics.
2. In the scheduler, if a heap check fails and we wanted more than
BLOCK_SIZE_W words, then allocate a special large block and place
it in the nursery. The nursery now has to be double-linked so
we can insert the new block in the middle.
3. The garbage collector has to be able to deal with multiple objects
in a large block. It turns out that this isn't a problem as long as
the large blocks only occur in the nursery, because we always copy
objects from the nursery during GC. One small change had to be
made: in evacuate(), we may need to follow the link field from the
block descriptor to get to the block descriptor for the head of a
large block.
4. Various other parts of the storage manager had to be modified
to cope with a nursery containing a mixture of block sizes.
Point (3) causes a slight pessimization in the garbage collector. I
don't see a way to avoid this. Point (1) causes some code bloat (a
rough measurement is around 5%), so to offset this I made the
following change which I'd been meaning to do for some time:
- Store the values of some commonly-used absolute addresses
(eg. stg_update_PAP) in the register table. This lets us use
shorter instruction forms for some absolute jumps and saves some
code space.
- The type of Capability is no longer the same as an StgRegTable.
MainRegTable renamed to MainCapability. See Regs.h for details.
Other minor changes:
- remove individual declarations for the heap-check-failure jump
points, and declare them all in StgMiscClosures.h instead. Remove
HeapStackCheck.h.
Updates to the native code generator to follow.
20 files changed: