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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id l63-v6si7760112plb.49.2018.05.18.12.45.23 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 18 May 2018 12:45:23 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=jxKijCps; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=References:In-Reply-To:Message-Id: Date:Subject:Cc:To:From:Sender:Reply-To:MIME-Version:Content-Type: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=zalGaDqBS4d2enUprStcmnkbSHARGTWptO06Ksi5rcI=; b=jxKijCpsKU29vPMHgjo1KLN1R 9AxmTMta9kBvqpw+qhFaVhzay+QRjF/Jx30g5uoLo7HzPA1N0llFeJmlY2tNbm+SdpBIUd4gZpuUB Qr+X4H/abTm/cNXVJ8FQbV+gb4RuyH8UgRfPtDBaTEumm19CZEV3NNFEuQBHIJAp29fNZKX1ebnlX v9wfEZsRWFSj6pIMMyEyIFzHyL6DmNSjy6rLb6f9W4sQIZwKapkaZvqEORefzT1HAcyniJAoAO/QX m0w4CyIof6o6vcop7na5QM/4Mzti+tkDZYPCbxe7f1Wm53g79I7T9r8g9XuILPQCDWYoacdDtCwzQ ZcmVzIyFQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1fJlJb-00011U-9b; Fri, 18 May 2018 19:45:23 +0000 From: Matthew Wilcox To: linux-mm@kvack.org Cc: Matthew Wilcox , Andrew Morton , "Kirill A . Shutemov" , Christoph Lameter , Lai Jiangshan , Pekka Enberg , Vlastimil Babka , Dave Hansen , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= Subject: [PATCH v6 10/17] mm: Combine LRU and main union in struct page Date: Fri, 18 May 2018 12:45:12 -0700 Message-Id: <20180518194519.3820-11-willy@infradead.org> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180518194519.3820-1-willy@infradead.org> References: <20180518194519.3820-1-willy@infradead.org> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Matthew Wilcox This gives us five words of space in a single union in struct page. The compound_mapcount moves position (from offset 24 to offset 20) on 64-bit systems, but that does not seem likely to cause any trouble. Signed-off-by: Matthew Wilcox Acked-by: Vlastimil Babka Acked-by: Kirill A. Shutemov --- include/linux/mm_types.h | 97 +++++++++++++++++++--------------------- mm/page_alloc.c | 2 +- 2 files changed, 47 insertions(+), 52 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index b6a3948195d3..cf3bbee8c9a1 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -73,59 +73,19 @@ struct page { unsigned long flags; /* Atomic flags, some possibly * updated asynchronously */ /* - * WARNING: bit 0 of the first word encode PageTail(). That means - * the rest users of the storage space MUST NOT use the bit to + * Five words (20/40 bytes) are available in this union. + * WARNING: bit 0 of the first word is used for PageTail(). That + * means the other users of this union MUST NOT use the bit to * avoid collision and false-positive PageTail(). */ - union { - struct list_head lru; /* Pageout list, eg. active_list - * protected by zone_lru_lock ! - * Can be used as a generic list - * by the page owner. - */ - struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an - * lru or handled by a slab - * allocator, this points to the - * hosting device page map. - */ - struct { /* slub per cpu partial pages */ - struct page *next; /* Next partial slab */ -#ifdef CONFIG_64BIT - int pages; /* Nr of partial slabs left */ - int pobjects; /* Approximate # of objects */ -#else - short int pages; - short int pobjects; -#endif - }; - - struct rcu_head rcu_head; /* Used by SLAB - * when destroying via RCU - */ - /* Tail pages of compound page */ - struct { - unsigned long compound_head; /* If bit zero is set */ - - /* First tail page only */ - unsigned char compound_dtor; - unsigned char compound_order; - /* two/six bytes available here */ - }; - -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS - struct { - unsigned long __pad; /* do not overlay pmd_huge_pte - * with compound_head to avoid - * possible bit 0 collision. - */ - pgtable_t pmd_huge_pte; /* protected by page->ptl */ - }; -#endif - }; - - /* Three words (12/24 bytes) are available in this union. */ union { struct { /* Page cache and anonymous pages */ + /** + * @lru: Pageout list, eg. active_list protected by + * zone_lru_lock. Sometimes used as a generic list + * by the page owner. + */ + struct list_head lru; /* See page-flags.h for PAGE_MAPPING_FLAGS */ struct address_space *mapping; pgoff_t index; /* Our offset within mapping. */ @@ -138,6 +98,19 @@ struct page { unsigned long private; }; struct { /* slab, slob and slub */ + union { + struct list_head slab_list; /* uses lru */ + struct { /* Partial pages */ + struct page *next; +#ifdef CONFIG_64BIT + int pages; /* Nr of pages left */ + int pobjects; /* Approximate count */ +#else + short int pages; + short int pobjects; +#endif + }; + }; struct kmem_cache *slab_cache; /* not slob */ /* Double-word boundary */ void *freelist; /* first free object */ @@ -151,9 +124,22 @@ struct page { }; }; }; - atomic_t compound_mapcount; /* first tail page */ - struct list_head deferred_list; /* second tail page */ + struct { /* Tail pages of compound page */ + unsigned long compound_head; /* Bit zero is set */ + + /* First tail page only */ + unsigned char compound_dtor; + unsigned char compound_order; + atomic_t compound_mapcount; + }; + struct { /* Second tail page of compound page */ + unsigned long _compound_pad_1; /* compound_head */ + unsigned long _compound_pad_2; + struct list_head deferred_list; + }; struct { /* Page table pages */ + unsigned long _pt_pad_1; /* compound_head */ + pgtable_t pmd_huge_pte; /* protected by page->ptl */ unsigned long _pt_pad_2; /* mapping */ unsigned long _pt_pad_3; #if ALLOC_SPLIT_PTLOCKS @@ -162,6 +148,15 @@ struct page { spinlock_t ptl; #endif }; + + /** @rcu_head: You can use this to free a page by RCU. */ + struct rcu_head rcu_head; + + /** + * @pgmap: For ZONE_DEVICE pages, this points to the hosting + * device page map. + */ + struct dev_pagemap *pgmap; }; union { /* This union is 4 bytes in size. */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1a0149c4f672..787440218def 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -924,7 +924,7 @@ static int free_tail_pages_check(struct page *head_page, struct page *page) } switch (page - head_page) { case 1: - /* the first tail page: ->mapping is compound_mapcount() */ + /* the first tail page: ->mapping may be compound_mapcount() */ if (unlikely(compound_mapcount(page))) { bad_page(page, "nonzero compound_mapcount", 0); goto out;