[PATCH] VM instrumentation

[PATCH] VM instrumentation

A patch from Rik which adds some operational statitics to the VM.

In /proc/meminfo:

PageTables:	Amount of memory used for process pagetables
PteChainTot:	Amount of memory allocated for pte_chain objects
PteChainUsed:	Amount of memory currently in use for pte chains.

In /proc/stat:

pageallocs:	Number of pages allocated in the page allocator
pagefrees:	Number of pages returned to the page allocator

		(These can be used to measure the allocation rate)

pageactiv:	Number of pages activated (moved to the active list)
pagedeact:	Number of pages deactivated (moved to the inactive list)
pagefault:	Total pagefaults
majorfault:	Major pagefaults
pagescan:	Number of pages which shrink_cache looked at
pagesteal:	Number of pages which shrink_cache freed
pageoutrun:	Number of calls to try_to_free_pages()
allocstall:	Number of calls to balance_classzone()

Rik will be writing a userspace app which interprets these things.

The /proc/meminfo stats are efficient, but the /proc/stat accumulators
will cause undesirable cacheline bouncing.  We need to break the disk
statistics out of struct kernel_stat and make everything else in there
per-cpu.  If that doesn't happen in time for 2.6 then we disable
KERNEL_STAT_INC().