Messages in this thread |  | | | Date | Fri, 30 Jul 2010 18:32:04 +0900 | | Subject | Re: [PATCH] Tight check of pfn_valid on sparsemem - v4 | | From | Minchan Kim <> |
| |
On Fri, Jul 30, 2010 at 5:55 AM, Dave Hansen <dave@linux.vnet.ibm.com> wrote: > On Thu, 2010-07-29 at 19:33 +0100, Russell King - ARM Linux wrote: >> And no, setting the sparse section size to 512kB doesn't work - memory is >> offset by 256MB already, so you need a sparsemem section array of 1024 >> entries just to cover that - with the full 256MB populated, that's 512 >> unused entries followed by 512 used entries. That too is going to waste >> memory like nobodies business. > > Sparsemem could use some work in the case where memory doesn't start at > 0x0. But, it doesn't seem like it would be _too_ oppressive to add. > It's literally just adding an offset to all of the places where a > physical address is stuck into the system. It'll make a few of the > calculations longer, of course, but it should be manageable. > > Could you give some full examples of how the memory is laid out on these > systems? I'm having a bit of a hard time visualizing it. > > As Christoph mentioned, SPARSEMEM_EXTREME might be viable here, too. > > If you free up parts of the mem_map[] array, how does the buddy > allocator still work? I thought we required at 'struct page's to be > contiguous and present for at least 2^MAX_ORDER-1 pages in one go.
I think in that case, arch should define CONFIG_HOLES_IN_ZONE to prevent crash. But I am not sure hole architectures on ARM have been used it well. Kujkin's problem happens not buddy but walking whole pfn to echo min_free_kbytes.
> > -- Dave > >
-- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |