memory tiering: skip to scan fast memory

If the NUMA balancing isn't used to optimize the page placement among
sockets but only among memory types, the hot pages in the fast memory
node couldn't be migrated (promoted) to anywhere.  So it's unnecessary
to scan the pages in the fast memory node via changing their PTE/PMD
mapping to be PROT_NONE.  So that the page faults could be avoided too.

In the test, if only the memory tiering NUMA balancing mode is enabled,
the number of the NUMA balancing hint faults for the DRAM node is
reduced to almost 0 with the patch.  While the benchmark score doesn't
change visibly.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: "Huang, Ying" <[email protected]>
Suggested-by: Dave Hansen <[email protected]>
Tested-by: Baolin Wang <[email protected]>
Reviewed-by: Baolin Wang <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Reviewed-by: Oscar Salvador <[email protected]>
Reviewed-by: Yang Shi <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: Wei Xu <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: zhongjiang-ali <[email protected]>
Cc: Feng Tang <[email protected]>
Cc: Randy Dunlap <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions