On Thu, Mar 11, 2010 at 10:04:36AM +0100, Francesc Alted wrote:
As far as I know, memmap files (or better, the underlying OS) *use* all available RAM for loading data until RAM is exhausted and then start to use SWAP, so the "memory pressure" is still there. But I may be wrong...
I believe that your above assertion is 'half' right. First I think that it is not SWAP that the memapped file uses, but the original disk space, thus you avoid running out of SWAP. Second, if you open several times the same data without memmapping, I believe that it will be duplicated in memory. On the other hand, when you memapping, it is not duplicated, thus if you are running several processing jobs on the same data, you save memory. I am very much in this case. Gaël