From: Andrew Morton <akpm@linux-foundation.org>
To: mm-commits@vger.kernel.org,alexs@kernel.org,david@redhat.com,akpm@linux-foundation.org
Subject: [merged mm-stable] mm-ksm-remove-page_mapcount-usage-in-stable_tree_search.patch removed from -mm tree
Date: Sun, 05 May 2024 17:57:33 -0700 [thread overview]
Message-ID: <20240506005733.98D5BC113CC@smtp.kernel.org> (raw)
The quilt patch titled
Subject: mm/ksm: remove page_mapcount() usage in stable_tree_search()
has been removed from the -mm tree. Its filename was
mm-ksm-remove-page_mapcount-usage-in-stable_tree_search.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: mm/ksm: remove page_mapcount() usage in stable_tree_search()
Date: Tue, 16 Apr 2024 19:25:33 +0200
We want to limit the use of page_mapcount() to the places where it is
absolutely necessary.
If our folio has a stable node, it is a (small) KSM folio -- see
folio_stable_node(). Let's use folio_mapcount() in stable_tree_search()
instead, which results in no functional change.
The mapcount > 1 check is a bit confusing, because that's usually a check
for page sharing. Looks like the reason is that we are guaranteed to not
exceed ksm_max_page_sharing for the tree KSM folio when merging with that.
Let's update the documentation to make that clearer.
Link: https://lkml.kernel.org/r/20240416172533.663418-1-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Alex Shi <alexs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/ksm.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
--- a/mm/ksm.c~mm-ksm-remove-page_mapcount-usage-in-stable_tree_search
+++ a/mm/ksm.c
@@ -1909,12 +1909,15 @@ again:
if (page_node) {
VM_BUG_ON(page_node->head != &migrate_nodes);
/*
- * Test if the migrated page should be merged
- * into a stable node dup. If the mapcount is
- * 1 we can migrate it with another KSM page
- * without adding it to the chain.
+ * If the mapcount of our migrated KSM folio is
+ * at most 1, we can merge it with another
+ * KSM folio where we know that we have space
+ * for one more mapping without exceeding the
+ * ksm_max_page_sharing limit: see
+ * chain_prune(). This way, we can avoid adding
+ * this stable node to the chain.
*/
- if (page_mapcount(page) > 1)
+ if (folio_mapcount(folio) > 1)
goto chain_append;
}
_
Patches currently in -mm which might be from david@redhat.com are
reply other threads:[~2024-05-06 0:57 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240506005733.98D5BC113CC@smtp.kernel.org \
--to=akpm@linux-foundation.org \
--cc=alexs@kernel.org \
--cc=david@redhat.com \
--cc=mm-commits@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).