On 11/13/2023 6:53 PM, David Hildenbrand wrote:
On 13.11.23 11:45, Baolin Wang wrote:
Currently, the file pages already support large folio, and supporting for
anonymous pages is also under discussion[1]. Moreover, the numa balancing
code are converted to use a folio by previous thread[2], and the
migrate_pages
function also already supports the large folio migration.
So now I did not see any reason to continue restricting NUMA balancing
for
large folio.
I recall John wanted to look into that. CCing him.
I'll note that the "head page mapcount" heuristic to detect sharers will
now strike on the PTE path and make us believe that a large folios is
exclusive, although it isn't.
As spelled out in the commit you are referencing:
commit 6695cf68b15c215d33b8add64c33e01e3cbe236c
Author: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Date: Thu Sep 21 15:44:14 2023 +0800
mm: memory: use a folio in do_numa_page()
Numa balancing only try to migrate non-compound page in
do_numa_page(),
use a folio in it to save several compound_head calls, note we use
folio_estimated_sharers(), it is enough to check the folio sharers
since
only normal page is handled, if large folio numa balancing is
supported, a
precise folio sharers check would be used, no functional change
intended.
Thanks for pointing out the part I missed.
I saw the migrate_pages() syscall is also using
folio_estimated_sharers() to check if the folio is shared, and I wonder
it will bring about any significant issues?
I'll send WIP patches for one approach that can improve the situation
soonish.
Great. Look forward to seeing this:)
