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Message-Id: <20210712030701.4000097-8-willy@infradead.org>
Date: Mon, 12 Jul 2021 04:04:51 +0100
From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
To: linux-kernel@...r.kernel.org
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>,
linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
Zi Yan <ziy@...dia.com>, Christoph Hellwig <hch@....de>,
Jeff Layton <jlayton@...nel.org>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Vlastimil Babka <vbabka@...e.cz>,
William Kucharski <william.kucharski@...cle.com>,
David Howells <dhowells@...hat.com>
Subject: [PATCH v13 007/137] mm: Add folio_put()
If we know we have a folio, we can call folio_put() instead of put_page()
and save the overhead of calling compound_head(). Also skips the
devmap checks.
This commit looks like it should be a no-op, but actually saves 684 bytes
of text with the distro-derived config that I'm testing. Some functions
grow a little while others shrink. I presume the compiler is making
different inlining decisions.
Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Reviewed-by: Zi Yan <ziy@...dia.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Acked-by: Jeff Layton <jlayton@...nel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Reviewed-by: William Kucharski <william.kucharski@...cle.com>
Reviewed-by: David Howells <dhowells@...hat.com>
---
include/linux/mm.h | 33 ++++++++++++++++++++++++++++-----
1 file changed, 28 insertions(+), 5 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 460e9805dd9f..c981e3b28eb0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -749,6 +749,11 @@ static inline int put_page_testzero(struct page *page)
return page_ref_dec_and_test(page);
}
+static inline int folio_put_testzero(struct folio *folio)
+{
+ return put_page_testzero(&folio->page);
+}
+
/*
* Try to grab a ref unless the page has a refcount of zero, return false if
* that is the case.
@@ -1245,9 +1250,28 @@ static inline __must_check bool try_get_page(struct page *page)
return true;
}
+/**
+ * folio_put - Decrement the reference count on a folio.
+ * @folio: The folio.
+ *
+ * If the folio's reference count reaches zero, the memory will be
+ * released back to the page allocator and may be used by another
+ * allocation immediately. Do not access the memory or the struct folio
+ * after calling folio_put() unless you can be sure that it wasn't the
+ * last reference.
+ *
+ * Context: May be called in process or interrupt context, but not in NMI
+ * context. May be called while holding a spinlock.
+ */
+static inline void folio_put(struct folio *folio)
+{
+ if (folio_put_testzero(folio))
+ __put_page(&folio->page);
+}
+
static inline void put_page(struct page *page)
{
- page = compound_head(page);
+ struct folio *folio = page_folio(page);
/*
* For devmap managed pages we need to catch refcount transition from
@@ -1255,13 +1279,12 @@ static inline void put_page(struct page *page)
* need to inform the device driver through callback. See
* include/linux/memremap.h and HMM for details.
*/
- if (page_is_devmap_managed(page)) {
- put_devmap_managed_page(page);
+ if (page_is_devmap_managed(&folio->page)) {
+ put_devmap_managed_page(&folio->page);
return;
}
- if (put_page_testzero(page))
- __put_page(page);
+ folio_put(folio);
}
/*
--
2.30.2
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