On Wed 22-05-13 12:49:37, Michal Hocko wrote:
> On Wed 22-05-13 17:29:27, Wanpeng Li wrote:
> > Logic memory-remove code fails to correctly account the Total High Memory
> > when a memory block which contains High Memory is offlined as shown in the
> > example below. The following patch fixes it.
> >
> > cat /proc/meminfo
> > MemTotal: 7079452 kB
> > MemFree: 5805976 kB
> > Buffers: 94372 kB
> > Cached: 872000 kB
> > SwapCached: 0 kB
> > Active: 626936 kB
> > Inactive: 519236 kB
> > Active(anon): 180780 kB
> > Inactive(anon): 222944 kB
> > Active(file): 446156 kB
> > Inactive(file): 296292 kB
> > Unevictable: 0 kB
> > Mlocked: 0 kB
> > HighTotal: 7294672 kB
> > HighFree: 5181024 kB
> > LowTotal: 4294752076 kB
> > LowFree: 624952 kB
>
> Ok, so the HighTotal is higher than MemTotal but it would have been more
> straightforward to show number of HighTotal before hotremove, show how
> much memory has been removed and the number after.
>
> It is not clear which stable kernels need this fix as well.
>
> >
> > Signed-off-by: Wanpeng Li <liw...@linux.vnet.ibm.com>
>
> Anyway
> Reviewed-by: Michal Hocko <mho...@suse.cz>
>
> with a nit pick bellow
>
> > ---
> > mm/page_alloc.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 98cbdf6..80474b2 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -6140,6 +6140,10 @@ __offline_isolated_pages(unsigned long start_pfn,
> > unsigned long end_pfn)
> > list_del(&page->lru);
> > rmv_page_order(page);
> > zone->free_area[order].nr_free--;
> > +#ifdef CONFIG_HIGHMEM
> > + if (PageHighMem(page))
> > + totalhigh_pages -= 1 << order;
> > +#endif
Hmm, it seems that my old gcc (4.3.4) doesn't like this.
mm/page_alloc.c:6202: error: lvalue required as left operand of assignment
I am not sure this is a compiler bug because PAGEFLAG_FALSE is clearly
returning 0 which should make the whole if a no-op... But maybe we
shouldn't be more clever than compiler.
Andrew, could you fold this follow up fix for
mm-memory-hotplug-fix-lowmem-count-overflow-when-offline-pages.patch
Sorr about the confusion I brought to this.
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 717286e..c164e5f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6198,8 +6198,10 @@ __offline_isolated_pages(unsigned long start_pfn,
unsigned long end_pfn)
list_del(&page->lru);
rmv_page_order(page);
zone->free_area[order].nr_free--;
+#ifdef CONFIG_HIGHMEM
if (PageHighMem(page))
totalhigh_pages -= 1 << order;
+#endif
for (i = 0; i < (1 << order); i++)
SetPageReserved((page+i));
pfn += (1 << order);
--
Michal Hocko
SUSE Labs
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