On (20/07/07 22:39), KAMEZAWA Hiroyuki didst pronounce: > On Fri, 20 Jul 2007 20:42:46 +0900 > Paul Mundt <[EMAIL PROTECTED]> wrote: > > > > I expect that the memory gets added to the same zone as historically but > > > when ZONE_MOVABLE is set, you'll see a situation where zones are > > > overlapping > > > after memory hot-add. i.e. Before memory hot-add, you'd see > > > > > > DDDDMM > > > > > > for ZONE_DMA and ZONE_MOVABLE and after hotadd, you'd see something like > > > > > > DDDDMMDDDD > > > > > As similar case, I hear powerpc has followig memory layout > > (1)(1)(0)(0)(0)(1)(1)(1) # (0) is node 0, (1) is node 1. all zones are > ZONE_DMA. >
Not always, but it happens. We used to have two test machines available that exhibited this behaviour although they went missing at some point which is unfortunate. > So zone is overlapped without memory hotplug. Zones overlapping have some subtle differences to nodes but the place this is really noticeable is during memory init when a range of PFNs are initialised by memmap_init_zone(). If zones overlap there, they can initialise the struct page fields twice but that is not an issue with memory hot-add. The potential issue I am thinking of is users that manually walk the memmap but no functionality outside of debugging should be doing anything like that. > But I agree we have to take care of this kind of corner cases. > Indeed. I think we're ok, but it should be checked out anyway. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
