On Wed, Sep 02, 2009 at 09:56:40AM -0700, Luck, Tony wrote: > > I wonder why you have DISCONTIGMEM_DEFAULT selected for GENERIC, SN2, and > ZX1? > > You don't explicitly disable SPARSEMEM for those platforms I think, so is > > there another reason than bugs for this? > > On ia64 DISCONTIGMEM was implemented first. SPARSEMEM came later, and > nobody has sent patches to switch the config defaults over to use it. > I'd love it if somebody came up with some definitive arguments for > why SPARSEMEM can replace DISCONTIGMEM so we could clear out some of > the clutter that has accumulated by having both implementations. Last > time I looked (a very long time ago) it looked like SPARSEMEM would > have difficulties handling the extreme levels of sparseness on the > SN2 platform (high order physical address bits are used to route > memory traffic to the right node ... and since SN2 supports a lot > of nodes, the bits in question are way up high). Not too sure. SPARSEMEM certainly can handle sparseness within a node better than DISCONTIGMEM I think (discontigmem is basically like a flat mem per-node so it gets redundant mem_map over holes within a node). I figured it was probably something to do with sn2, but I wondered about bugs in the other cases too. > > My followup question... I wonder why memory hotplug is disabled for > > discontigmem? It seems like there is code there to handle it (athough > > I don't know the memory hotplug code well so I didn't look too closely). > > Not at all sure of the history for this one. OK, I thought I'd ask here because some of the ia64 people are involved in developing mem hotplug. Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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