On 01/10/2013 04:46 PM, paul.szabo@xxxxxxxxxxxxx wrote: >> Your configuration has never worked. This isn't a regression ... >> ... does not mean that we expect it to work. > > Do you mean that CONFIG_HIGHMEM64G is deprecated, should not be used; > that all development is for 64-bit only? My last 4GB laptop had a 1GB hole and needed HIGHMEM64G since it had RAM at 0->5GB. That worked just fine, btw. The problem isn't with HIGHMEM64G itself. I'm not saying HIGHMEM64G is inherently bad, just that it gets gradually worse and worse as you add more RAM. I don't believe 64GB of RAM has _ever_ been booted on a 32-bit kernel without either violating the ABI (3GB/1GB split) or doing something that never got merged upstream (that 4GB/4GB split, or other fun stuff like page clustering). > I find it puzzling that there seems to be a sharp cutoff at 32GB RAM, > no problem under but OOM just over; whereas I would have expected > lowmem starvation to be gradual, with OOM occuring much sooner with > 64GB than with 34GB. Also, the kernel seems capable of reclaiming > lowmem, so I wonder why does that fail just over the 32GB threshhold. > (Obviously I have no idea what I am talking about.) It _is_ puzzling. It isn't immediately obvious to me why the slab that you have isn't being reclaimed. There might, indeed, be a fixable bug there. But, there are probably a bunch more bugs which will keep you from having a nice, smoothly-running system, mostly those bugs have not had much attention in the 10 years or so since 64-bit x86 became commonplace. Plus, even 10 years ago, when folks were working on this actively, we _never_ got things running smoothly on 32GB of RAM. Take a look at this: http://support.bull.com/ols/product/system/linux/redhat/help/kbf/g/inst/PrKB11417 You are effectively running the "SMP kernel" (hugemem is a completely different beast). I had a 32GB i386 system. It was a really, really fun system to play with, and its never-ending list of bugs helped keep me employed for several years. You don't want to unnecessarily inflict that pain on yourself, really. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>