On Tue, Aug 24, 2010 at 3:43 PM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > At Tue, 24 Aug 2010 09:53:21 -0700, Joe Marshall wrote: >> I'm surprised that racket3m uses page protection. Taking a hardware trap >> can often be thousands of times slower than taking an inline conditional >> branch. > > The hardware trap happens once per GC-managed page between minor > collections, while the inline condition happens every time an > assignment is performed.
Right, but you have to have a marking granularity that is equal to the page size. Hosking and Moss discovered that card marking can be competitive with or faster than using the hardware. > > I haven't been able to construct a program that mutates many pages a > small number of times between collections, thus maximizing the relative > cost of the trap versus a potential implementation with an inline > conditional; does enough work to trigger collections; and performs > little enough work relative to mutation so that the barrier cost is > measurable. Does Will Clinger have any data? -- ~jrm _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
