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Date:   Fri, 26 Feb 2021 02:17:18 -0700
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Subject: [PATCH v2 3/3] mm: use PF_ONLY_HEAD for PG_active and PG_unevictable
From:   Yu Zhao <yuzhao@google.com>
To:     akpm@linux-foundation.org, alex.shi@linux.alibaba.com,
        vbabka@suse.cz, willy@infradead.org
Cc:     guro@fb.com, hannes@cmpxchg.org, hughd@google.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        mhocko@kernel.org, vdavydov.dev@gmail.com,
        Yu Zhao <yuzhao@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

All places but one test, set or clear PG_active and PG_unevictable on
small or head pages. Use compound_head() explicitly for that singleton
so the rest can rid of redundant compound_head().

bloat-o-meter result:
  add/remove: 0/0 grow/shrink: 3/38 up/down: 388/-4270 (-3882)

Signed-off-by: Yu Zhao <yuzhao@google.com>
---
 fs/proc/task_mmu.c         |  3 ++-
 include/linux/page-flags.h | 10 +++++-----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3cec6fbef725..c866c363bb41 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1712,6 +1712,7 @@ static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty,
 			unsigned long nr_pages)
 {
 	int count = page_mapcount(page);
+	struct page *head = compound_head(page);
 
 	md->pages += nr_pages;
 	if (pte_dirty || PageDirty(page))
@@ -1720,7 +1721,7 @@ static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty,
 	if (PageSwapCache(page))
 		md->swapcache += nr_pages;
 
-	if (PageActive(page) || PageUnevictable(page))
+	if (PageActive(head) || PageUnevictable(head))
 		md->active += nr_pages;
 
 	if (PageWriteback(page))
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index c9626e54df8d..b7fe855a6ee9 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -335,8 +335,8 @@ PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFLAG(Dirty, dirty, PF_HEAD)
 	__CLEARPAGEFLAG(Dirty, dirty, PF_HEAD)
 PAGEFLAG(LRU, lru, PF_NO_TAIL) __CLEARPAGEFLAG(LRU, lru, PF_NO_TAIL)
 	TESTCLEARFLAG(LRU, lru, PF_NO_TAIL)
-PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
-	TESTCLEARFLAG(Active, active, PF_HEAD)
+PAGEFLAG(Active, active, PF_ONLY_HEAD) __CLEARPAGEFLAG(Active, active, PF_ONLY_HEAD)
+	TESTCLEARFLAG(Active, active, PF_ONLY_HEAD)
 PAGEFLAG(Workingset, workingset, PF_HEAD)
 	TESTCLEARFLAG(Workingset, workingset, PF_HEAD)
 __PAGEFLAG(Slab, slab, PF_NO_TAIL)
@@ -407,9 +407,9 @@ CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
 PAGEFLAG_FALSE(SwapCache)
 #endif
 
-PAGEFLAG(Unevictable, unevictable, PF_HEAD)
-	__CLEARPAGEFLAG(Unevictable, unevictable, PF_HEAD)
-	TESTCLEARFLAG(Unevictable, unevictable, PF_HEAD)
+PAGEFLAG(Unevictable, unevictable, PF_ONLY_HEAD)
+	__CLEARPAGEFLAG(Unevictable, unevictable, PF_ONLY_HEAD)
+	TESTCLEARFLAG(Unevictable, unevictable, PF_ONLY_HEAD)
 
 #ifdef CONFIG_MMU
 PAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
-- 
2.30.1.766.gb4fecdf3b7-goog