From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 4BC3F6B0169 for ; Tue, 9 Aug 2011 11:04:08 -0400 (EDT) MIME-Version: 1.0 Message-ID: Date: Tue, 9 Aug 2011 08:03:43 -0700 (PDT) From: Dan Magenheimer Subject: RE: Subject: [PATCH V6 1/4] mm: frontswap: swap data structure changes References: <20110808204555.GA15850@ca-server1.us.oracle.com 4E414320020000780005057E@nat28.tlf.novell.com> In-Reply-To: <4E414320020000780005057E@nat28.tlf.novell.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Jan Beulich Cc: hannes@cmpxchg.org, jackdachef@gmail.com, hughd@google.com, jeremy@goop.org, npiggin@kernel.dk, linux-mm@kvack.org, akpm@linux-foundation.org, sjenning@linux.vnet.ibm.com, Chris Mason , Konrad Wilk , Kurt Hackel , riel@redhat.com, ngupta@vflare.org, linux-kernel@vger.kernel.org, matthew@wil.cx > > --- linux/include/linux/swap.h=092011-08-08 08:19:25.880690134 -0600 > > +++ frontswap/include/linux/swap.h=092011-08-08 08:59:03.952691415 -060= 0 > > @@ -194,6 +194,8 @@ struct swap_info_struct { > > =09struct block_device *bdev;=09/* swap device or bdev of swap file */ > > =09struct file *swap_file;=09=09/* seldom referenced */ > > =09unsigned int old_block_size;=09/* seldom referenced */ >=20 > #ifdef CONFIG_FRONTSWAP >=20 > > +=09unsigned long *frontswap_map;=09/* frontswap in-use, one bit per pa= ge */ > > +=09unsigned int frontswap_pages;=09/* frontswap pages in-use counter *= / >=20 >=20 > #endif >=20 > (to eliminate any overhead with that config option unset) >=20 > Jan Hi Jan -- Thanks for the review! As noted in the commit comment, if these structure elements are not put inside an #ifdef CONFIG_FRONTSWAP, it becomes unnecessary to clutter the core swap code with several ifdefs. The cost is one pointer and one unsigned int per allocated swap device (often no more than one swap device per system), so the code clarity seemed more important than the tiny additional runtime space cost. Do you disagree? Thanks, Dan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org