patches/old/trace-events-page_ref-trace-the-raw-page-mapcount-value.patch

From: David Hildenbrand <david@redhat.com>
Subject: trace/events/page_ref: trace the raw page mapcount value
Date: Tue, 9 Apr 2024 21:22:58 +0200

We want to limit the use of page_mapcount() to the places where it is
absolutely necessary.  We already trace raw page->refcount, raw
page->flags and raw page->mapping, and don't involve any folios.  Let's
also trace the raw mapcount value that does not consider the entire
mapcount of large folios, and we don't add "1" to it.

When dealing with typed folios, this makes a lot more sense.  ...  and
it's for debugging purposes only either way.

Link: https://lkml.kernel.org/r/20240409192301.907377-16-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/trace/events/page_ref.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/include/trace/events/page_ref.h~trace-events-page_ref-trace-the-raw-page-mapcount-value
+++ a/include/trace/events/page_ref.h
@@ -30,7 +30,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_templat
 		__entry->pfn = page_to_pfn(page);
 		__entry->flags = page->flags;
 		__entry->count = page_ref_count(page);
-		__entry->mapcount = page_mapcount(page);
+		__entry->mapcount = atomic_read(&page->_mapcount);
 		__entry->mapping = page->mapping;
 		__entry->mt = get_pageblock_migratetype(page);
 		__entry->val = v;
@@ -79,7 +79,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_and_tes
 		__entry->pfn = page_to_pfn(page);
 		__entry->flags = page->flags;
 		__entry->count = page_ref_count(page);
-		__entry->mapcount = page_mapcount(page);
+		__entry->mapcount = atomic_read(&page->_mapcount);
 		__entry->mapping = page->mapping;
 		__entry->mt = get_pageblock_migratetype(page);
 		__entry->val = v;
_