Taste

Posted Sep 7, 2007 23:53 UTC (Fri) by jsnell (guest, #47245) [Link]

Lest anyone be confused: CMUCL and SBCL's garbage collectors are essentially identical, and CMUCL has had a generational garbage collector since...a very long time ago.

While the code in the two GCs might be essentially identical, that doesn't really mean that their performance characteristics are. There are many important performance improvements in the memory management of sbcl which never made it back to cmucl. Some of those improvements were in the GC, others in related areas like the fast path of the memory allocation sequence. As a result of those, cmucl can take 2x the time sbcl does to run an allocation-heavy program and spend 5x as long in the GC for it [*].

But ultimately those improvements were just tweaks on a 10 year old GC that uses only concepts that are 20 year old, and which was bolted on to a compiler that doesn't really provide any support for the GC. It's not hard to imagine that newer GC designs or ones that are properly integrated into the compiler would perform even better.

[*] Those results are from the Alioth binary-trees benchmark with n=20, since I don't have any better benchmarks accessible right now. Incidentally, in the shootout results the Lisp version of this program is faster than the C one.