On Saturday 14 March 2009, Nick Piggin wrote: > On Sunday 15 March 2009 14:24:29 Daniel Phillips wrote: > > I expect implementing VM extents to be a brutally complex project, as > > filesystem extents always turn out to be, even though one tends to > > enter such projects thinking, how hard could this be? Answer: harder > > than you think. But VM extents would be good for a modest speedup, so > > somebody is sure to get brave enough to try it sometime. > > I don't think there is enough evidence to be able to make such an > assertion. > > When you actually implement extent splitting and merging in a deadlock > free manner and synchronize everything properly I wouldn't be surprised > if it is slower most of the time. If it was significantly faster, then > memory fragmentation means that it is going to get significantly slower > over the uptime of the kernel, so you would have to virtually map the > kernel and implement memory defragmentation, at which point you get even > slower and more complex. You can make exactly the same argument about filesystem extents, and we know that extents are faster there. So what is the fundamental difference? Regards, Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
