mm/vmstat: switch counter modification to cmpxchg

mm/vmstat: switch counter modification to cmpxchg

In preparation for switching vmstat shepherd to flush per-CPU counters
remotely, switch the __{mod,inc,dec} functions that modify the counters to
use cmpxchg.

To facilitate reviewing, functions are ordered in the text file, as:

__{mod,inc,dec}_{zone,node}_page_state
#ifdef CONFIG_HAVE_CMPXCHG_LOCAL
{mod,inc,dec}_{zone,node}_page_state
#else
{mod,inc,dec}_{zone,node}_page_state
#endif

This patch defines the __ versions for the
CONFIG_HAVE_CMPXCHG_LOCAL case to be their non-"__" counterparts:

#ifdef CONFIG_HAVE_CMPXCHG_LOCAL
{mod,inc,dec}_{zone,node}_page_state
__{mod,inc,dec}_{zone,node}_page_state = {mod,inc,dec}_{zone,node}_page_state
#else
{mod,inc,dec}_{zone,node}_page_state
__{mod,inc,dec}_{zone,node}_page_state
#endif

To test the performance difference, a page allocator microbenchmark:
https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/bench/page_bench01.c
with loops=1000000 was used, on Intel Core i7-11850H @ 2.50GHz.

For the single_page_alloc_free test, which does

        /** Loop to measure **/
        for (i = 0; i < rec->loops; i++) {
                my_page = alloc_page(gfp_mask);
                if (unlikely(my_page == NULL))
                        return 0;
                __free_page(my_page);
        }

Unit is cycles.

Vanilla			Patched		Diff
115.25			117		1.4%

Link: https://lkml.kernel.org/r/20230320180745.733575720@redhat.com
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Aaron Tomlin <atomlin@atomlin.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>