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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id q199si8453425pfq.112.2019.07.12.06.50.04 for (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 12 Jul 2019 06:50:04 -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=cxBzmFcO; 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=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: 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=fnnfXjFvjoDoIQnQuaRvGkZvYrw5HXbBFVcsaXovgKE=; b=cxBzmFcOfyCVzsiypcmiuOaB4 1fMOmo+ZpbRPzJh+dTAYCbGidK6YiB8fbVv+neUEMBO1XgD5lFgobanIPl08Mxk/kB4jbRHgSXVIu aCrx/4k1V+9nWoRLBofxtdG0zd64VyyVgfuiwVS4CYteqh5B/2nbBOW5hf5MTuWwDcRHDCn+/Nc3s kYe9yq9chH57EPO3w0dPdAmX2U5O3eJJvSfg/Gh1ezFs3FNLWsIKC+otRLOEJ92WvN6OkgNGvm8zt FQ0G1NL4KUEWiWWE3e355AGY9P4U+l/lSbUFWthv4KVBi3Bml3xpaj7zCqeXdvrhPgklF9DUhNVjI jOn4gFOmA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hlvvv-0007EF-C1; Fri, 12 Jul 2019 13:49:55 +0000 Date: Fri, 12 Jul 2019 06:49:55 -0700 From: Matthew Wilcox To: Pengfei Li Cc: akpm@linux-foundation.org, urezki@gmail.com, rpenyaev@suse.de, peterz@infradead.org, guro@fb.com, rick.p.edgecombe@intel.com, rppt@linux.ibm.com, aryabinin@virtuozzo.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] mm/vmalloc.c: Modify struct vmap_area to reduce its size Message-ID: <20190712134955.GV32320@bombadil.infradead.org> References: <20190712120213.2825-1-lpf.vector@gmail.com> <20190712120213.2825-3-lpf.vector@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190712120213.2825-3-lpf.vector@gmail.com> User-Agent: Mutt/1.11.4 (2019-03-13) 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: On Fri, Jul 12, 2019 at 08:02:13PM +0800, Pengfei Li wrote: > +++ b/include/linux/vmalloc.h > @@ -51,15 +51,37 @@ struct vmap_area { > unsigned long va_start; > unsigned long va_end; > > - /* > - * Largest available free size in subtree. > - */ > - unsigned long subtree_max_size; > - unsigned long flags; > - struct rb_node rb_node; /* address sorted rbtree */ > - struct list_head list; /* address sorted list */ > - struct llist_node purge_list; /* "lazy purge" list */ > - struct vm_struct *vm; > + union { > + /* In rbtree and list sorted by address */ > + struct { > + union { > + /* > + * In "busy" rbtree and list. > + * rbtree root: vmap_area_root > + * list head: vmap_area_list > + */ > + struct vm_struct *vm; > + > + /* > + * In "free" rbtree and list. > + * rbtree root: free_vmap_area_root > + * list head: free_vmap_area_list > + */ > + unsigned long subtree_max_size; > + }; > + > + struct rb_node rb_node; > + struct list_head list; > + }; > + > + /* > + * In "lazy purge" list. > + * llist head: vmap_purge_list > + */ > + struct { > + struct llist_node purge_list; > + }; I don't think you need struct union struct union. Because llist_node is just a pointer, you can get the same savings with just: union { struct llist_node purge_list; struct vm_struct *vm; unsigned long subtree_max_size; };