On Thursday, 23 August 2012 at 11:40:22 UTC, Rory McGuire wrote:
On Thu, Aug 23, 2012 at 4:01 AM, Chad J
<chadjoan@__spam.is.bad__gmail.com>wrote:
Poolwise bitmap... what an interesting name. I'll look
forward to
learning about the concepts behind it!
+1
Basically, the idea is to store information about what is and
isn't a pointer at the pool level instead of at the block level.
My attempt from a long time ago at precise heap scanning, and
Antti-Ville's first attempt, stored meta-data at the end of every
allocated block. This worked well for large arrays, but was
terribly inefficient for smaller allocations and made the GC code
even messier than it already is. The overhead was a fixed
(void*).sizeof bits per block. Now, each pool has a bit array
that contains one bit for every possible aligned pointer. The
overhead is always 1 bit for every (void*).sizeof bytes no matter
how large or small the block is.
