Re: [PATCH -V3] NUMA balancing: reduce TLB flush via delaying mapping on hint page fault

[Mel Gorman]

On Thu, Apr 08, 2021 at 09:22:36PM +0800, Huang Ying wrote:
> With NUMA balancing, in hint page fault handler, the faulting page
> will be migrated to the accessing node if necessary.  During the
> migration, TLB will be shot down on all CPUs that the process has run
> on recently.  Because in the hint page fault handler, the PTE will be
> made accessible before the migration is tried.  The overhead of TLB
> shooting down can be high, so it's better to be avoided if possible.
> In fact, if we delay mapping the page until migration, that can be
> avoided.  This is what this patch doing.
> 

<SNIP>

> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Reviewed-by: Mel Gorman <mgorman@xxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Peter Xu <peterx@xxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: "Matthew Wilcox" <willy@xxxxxxxxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Michel Lespinasse <walken@xxxxxxxxxx>
> Cc: Arjun Roy <arjunroy@xxxxxxxxxx>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>

Hi Andrew,

I do not see this in the mmots tree. Was something missed in this patch
that needs fixing or did it just fall through the cracks?

Thanks.

-- 
Mel Gorman
SUSE Labs