Hi Zi Yan,
On Tue, Feb 13, 2024 at 04:55:13PM -0500, Zi Yan wrote:
From: Zi Yan ziy@nvidia.com
Hi all,
File folio supports any order and multi-size THP is upstreamed[1], so both file and anonymous folios can be >0 order. Currently, split_huge_page() only splits a huge page to order-0 pages, but splitting to orders higher than 0 is going to better utilize large folios. In addition, Large Block Sizes in XFS support would benefit from it[2]. This patchset adds support for splitting a large folio to any lower order folios and uses it during file folio truncate operations.
I added your patches on top of my patches, but removed patch 6 and I added this instead:
diff --git a/mm/truncate.c b/mm/truncate.c index 725b150e47ac..dd07e2e327a8 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -239,7 +239,8 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end) folio_invalidate(folio, offset, length); if (!folio_test_large(folio)) return true; - if (split_folio(folio) == 0) + if (split_folio_to_order(folio, + mapping_min_folio_order(folio->mapping)) == 0) return true; if (folio_test_dirty(folio)) return false;
I ran genric/476 fstest[1] with SOAK_DURATION set to 360 seconds. This test uses fstress to do a lot of writes, truncate operations, etc. I ran this on XFS with **64k block size on a 4k page size system**.
I recorded the vm event for split page and this was the result I got:
Before your patches: root@debian:~/xfstests# cat /proc/vmstat | grep split thp_split_page 0 thp_split_page_failed 5819
After your patches: root@debian:~/xfstests# cat /proc/vmstat | grep split thp_split_page 5846 thp_split_page_failed 20
Your patch series definitely helps with splitting the folios while still maintaining the min_folio_order that LBS requires.
We are still discussing how to quantify this benefit in terms of some metric with this support. If you have some ideas here, let me know.
I will run the whole xfstests tonight to check for any regressions.
-- Pankaj
[1] https://github.com/kdave/xfstests/blob/master/tests/generic/476