Pretty much what I had in mind. Don't forget that
ints are signed, so unless you just drop the high
bit, the watermark may not work. That's my concern.
I agree with Eddie that a fixed scheme may not work
for all deployments, so we would need to be flexible.
--Thilo
Marshall Schor wrote:
Here's a suggestion suggested by previous posts, and common hardware
design for segmented memory.
Take the int values that represent feature structure (fs) references.
Today, these are positive numbers from 1 (I think) to around 4 billion.
These values are used directly as an index into the heap.
Change this to split the bits in these int values into two parts, let's
call them upper and lower. For example
xxxx xxxx xxxx yyyy yyyy yyyy yyyy yyyy
where the xxx's are the upper bits (each x represents a hex digit), and
the y's the lower bits. The y's in this case can represent numbers up
to 1 million (approx), and the xxx's represent 4096 values.
Then allocate the heap using multiple 1 meg entry tables, and store each
one in the 4096 entry reference array. The heap reference would be some
bit-wise shifting and indexed lookup in addition to what we have now and
would probably be very fast, and could be optimized for the xxx=0 case
to be even faster.
This breaks heaps of over 1 meg into separate parts, which would make
them more managable, I think, and keeps the high-water mark method
viable, too.
Opinions?
-Marshall
