JEmalloc is a highly scalable memory allocator made by Jason Evans. This is the default allocator of the FreeBSD operating system and Firefox's Linux/Windows versions, but how does it perform in WebKit?
On SunSpider, TCmalloc is faster by 8.7% than JEmalloc. On V8, this value is only 6.4%. On WindScorpion benchmark suite, TCmalloc is 20% faster than JEmalloc... In all cases, System malloc is a bit faster than JEmalloc. Therefore, in all of the three cases, both the System allocator and TCmalloc performs better. I think we can't tweak JEmalloc to overtake TCmalloc's performance in the case of WindScorpion benchmark.
As we can see, JEmalloc's memory consumption stands between TCmalloc and System malloc. In all of the three benchmarks, system allocator's memory consumption shows the best values. By tweaking JEmalloc's parameters, we got close only to the System malloc's memory consumption, so I expect no more improvement from JEmalloc.
I think we shouldn't put more effort on JEmalloc, because system allocator is much better on these benchmarks... But, what do you think?