Re: [PATCH 1/3] mm, numa: rework do_pages_move

[Michal Hocko]

On Fri 05-01-18 11:15:18, Cristopher Lameter wrote:
> On Fri, 5 Jan 2018, Michal Hocko wrote:
> 
> > Yes. I am really wondering because there souldn't anything specific to
> > improve the situation with patch 2 and 3. Likewise the only overhead
> > from the patch 1 I can see is the reduced batching of the mmap_sem. But
> > then I am wondering what would compensate that later...
> 
> Could you reduce the frequency of taking mmap_sem? Maybe take it when
> picking a new node and drop it when done with that node before migrating
> the list of pages?

I believe there should be some cap on the number of pages. We shouldn't
keep it held for million of pages if all of them are moved to the same
node. I would really like to postpone that to later unless it causes
some noticeable regressions because this would complicate the code
further and I am not sure this is all worth it.

-- 
Michal Hocko
SUSE Labs