Re: [PATCH 0/5] fix up /proc/$pid/smaps to not split huge pages

On Tue, Feb 15, 2011 at 11:55:10AM -0500, Eric B Munson wrote:

I am noticing in smaps that KernelPageSize is wrong of areas
that have been merged into THP.  For instance:

7ff852a00000-7ff852c00000 rw-p 00000000 00:00 0 
Size:               2048 kB
Rss:                2048 kB
Pss:                2048 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:      2048 kB
Referenced:         2048 kB
Anonymous:          2048 kB
AnonHugePages:      2048 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Locked:                0 kB

The entire mapping is contained in a THP but the
KernelPageSize shows 4kb.  For cases where the mapping might
have mixed page sizes this may be okay, but for this
particular mapping the 4kb page size is wrong.

I'm not sure this is a bug, if the mapping grows it may become 4096k
but the new pages may be 4k. There's no such thing as a
vma_mmu_pagesize in terms of hugepages because we support graceful
fallback and collapse/split on the fly without altering the vma. So I
think 4k is correct here.

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