On Wednesday, 14 September 2016 at 07:16:04 UTC, deadalnix wrote:
On Wednesday, 14 September 2016 at 05:38:38 UTC, Shachar
Shemesh wrote:
On 14/09/16 02:59, Walter Bright wrote:
[...]
But if you do want to allow it, then my original problem comes
back. You have to scan the malloced memory because you are not
sure where that memory might contain pointers to GC managed
memory.
And the hybrid hybrid approach (i.e. - only some of the memory
allocated by malloc is scanned) is a wasp nest of potential
bugs and problems.
Shachar
Cool down, take a step back.
There are memory management technique that can give you good
result in most case, but will degenerate is few others. For
instance RC doesn't handle cycles, plays poorly with
exceptions, and so on.
There are ways to make RC work in all these case, but it is has
severe drawbacks. Now, if you allocate using a GC, and use RC
on top of it, you get 99% of the garbage cleaned up as you
expect. But it allows the RC system to just delegate to the GC
for cases it is not good at.
That way you get very occasional collection cycles to the point
where it is usually not a problem, and if you are smart about
it, you can even trigger them yourself at appropriate time. If
99% of the garbage is cleanup up by the RC mechanism, the the
garbage accumulate at 1% the rate of what it would with a 100%
GC system, and, consequently, you can run collection 1/100 time
what you would with a pure GC system with the same memory
overhead.
Now you may ask, how am I so sure that this is working great ?
The short answer is PHP.
As extra info, it was the approach taken by Cedar at Xerox PARC
as well.
RC for almost everything, with a local tracing GC for collecting
cycles.
https://archive.org/details/bitsavers_xeroxparcteCedarProgrammingEnvironmentAMidtermRepo_13518000
https://archive.org/details/bitsavers_xeroxparctddingGarbageCollectionandRuntimeTypestoa_1765837
