Lookaside Lists Vs Low fragmentation heap

Question

Can someone please explain the differences between those two. I know that the LFH wasn't enabled by default until Windows Vista , and the lookaside lists were used in XP.

Thanks

Answer 1

Succinctly, Look-aside lists are pre-allocated buffers that help you avoid taking the heap global lock by running lock-free - using compare and swap instructions. Where CAS are not available or suitable the list manager will revert to spin locks or fast mutexes. They are most suitable if you are writing a driver which uses a series of small fixed-size allocations, and were available since Windows 2000.

The Low fragmentation heap is a policy that you can enable for you heap and is generally not about avoiding the heap global lock as with LALs, but rather about improving performance in an arena with an expected fragmentation due to frequent allocations (and de-allocations) of different sizes.