Re: [PATCH -V13 3/3] memory tiering: skip to scan fast memory

[Oscar Salvador]

On Mon, Feb 21, 2022 at 04:45:29PM +0800, Huang Ying wrote:
> 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.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Suggested-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Yang Shi <shy828301@xxxxxxxxx>
> Cc: Zi Yan <ziy@xxxxxxxxxx>
> Cc: Wei Xu <weixugc@xxxxxxxxxx>
> Cc: Oscar Salvador <osalvador@xxxxxxx>
> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
> Cc: zhongjiang-ali <zhongjiang-ali@xxxxxxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx

Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>

-- 
Oscar Salvador
SUSE Labs