Messages in this thread Patch in this message | | | Date | Fri, 20 Jul 2007 12:20:25 +0100 | Subject | Re: [PATCH] mm: Fix memory hotplug oops from ZONE_MOVABLE changes. | From | (Mel Gorman) |
| |
On (20/07/07 15:03), Paul Mundt didst pronounce: > zone_movable_pfn is presently marked as __initdata and referenced > from adjust_zone_range_for_zone_movable(), which in turn is > referenced by zone_spanned_pages_in_node(). Both of these are > __meminit annotated. When memory hotplug is enabled, this will oops > on a hot-add, due to zone_movable_pfn having been freed. >
Ouch. Thanks for catching, your patch looks good. Before I add the ack though, I would like to get more details of the error in case there are other gremlins I haven't thought of and the fix for memory-hotadd is more complex.
First, can you confirm this is node hot-add please? I'm haven't looked at the memory hot-add code in a while so I would like to be sure this problem path only exists on node hot-add. If it is node hot-add, then everything should be ok. The memory should get added to the same zone as it did in older kernels.
Even if this is node hot-add, can you confirm that "ordinary" memory hot-add is working as expected when ZONE_MOVABLE exists please? To test, add a boot parameter kernelcore=N where N == 80% of memory and hot-add some memory to an existing node.
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
so /proc/zoneinfo will look unusual. I'd like to be sure the memory exists where you expect it to exist and that there are no problems after hot-add. To test, a simple memory hot-add followed by a dd of a file the size of all physical memory followed by a delete should do the trick. Also make sure files like /proc/zoneinfo and /proc/meminfo are ok and particularly that sysrq+m produces sensible output.
The only in-kernel user that should notice is one that is trying to walk the whole of memmap and is using page_zone() changing to detect boundaries. The existing users I am aware of only walk within a MAX_ORDER_NR_PAGES boundary usually and a memory section boundary at most. Those users will be ok even if zones overlap.
Thanks a lot.
If other memory-hotadd users are watching, I'd appreciate a test and a report with a recent -git kernel to confirm you're ok. Is there a way currently of simulating memory-hotadd so I can try this out? Ages ago, one could boot with mem= and "add" the remaining memory at run-time.
> __meminitdata annotation gives the desired behaviour. > > This will only impact platforms that enable both memory hotplug > and ARCH_POPULATES_NODE_MAP. > > Signed-off-by: Paul Mundt <lethal@linux-sh.org> > > -- > > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 43cb3b3..40954fb 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -138,7 +138,7 @@ static unsigned long __meminitdata dma_reserve; > #endif /* CONFIG_MEMORY_HOTPLUG_RESERVE */ > unsigned long __initdata required_kernelcore; > unsigned long __initdata required_movablecore; > - unsigned long __initdata zone_movable_pfn[MAX_NUMNODES]; > + unsigned long __meminitdata zone_movable_pfn[MAX_NUMNODES]; > > /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */ > int movable_zone;
-- -- 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 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/
| |