Quicklists can consume several GB of memory.  We should provide a means of
monitoring this.

After this patch is applied, /proc/meminfo will output the following:

% cat /proc/meminfo

MemTotal:      7715392 kB
MemFree:       5401600 kB
Buffers:         80384 kB
Cached:         300800 kB
SwapCached:          0 kB
Active:         235584 kB
Inactive:       262656 kB
SwapTotal:     2031488 kB
SwapFree:      2031488 kB
Dirty:            3520 kB
Writeback:           0 kB
AnonPages:      117696 kB
Mapped:          38528 kB
Slab:          1589952 kB
SReclaimable:    23104 kB
SUnreclaim:    1566848 kB
PageTables:      14656 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
WritebackTmp:        0 kB
CommitLimit:   5889152 kB
Committed_AS:   393152 kB
VmallocTotal: 17592177655808 kB
VmallocUsed:     29056 kB
VmallocChunk: 17592177626432 kB
Quicklists:     130944 kB
HugePages_Total:     0
HugePages_Free:      0
HugePages_Rsvd:      0
HugePages_Surp:      0
Hugepagesize:    262144 kB

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Keiichiro Tokunaga <tokunaga.keiich@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>