From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [PATCH] VFS: Cut down inode->i_op->xyz accesses in path walking Date: Tue, 26 Jul 2011 11:45:38 -0700 Message-ID: References: <20110726030531.GE22133@ZenIV.linux.org.uk> <20110726184122.GI22133@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Christoph Hellwig , linux-fsdevel To: Al Viro Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:58151 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752020Ab1GZSqA convert rfc822-to-8bit (ORCPT ); Tue, 26 Jul 2011 14:46:00 -0400 Received: from mail-wy0-f174.google.com (mail-wy0-f174.google.com [74.125.82.174]) (authenticated bits=0) by smtp1.linux-foundation.org (8.14.2/8.13.5/Debian-3ubuntu1.1) with ESMTP id p6QIjwsT030341 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=FAIL) for ; Tue, 26 Jul 2011 11:45:59 -0700 Received: by wyg8 with SMTP id 8so404614wyg.19 for ; Tue, 26 Jul 2011 11:45:58 -0700 (PDT) In-Reply-To: <20110726184122.GI22133@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Jul 26, 2011 at 11:41 AM, Al Viro wro= te: > > Hmm... =A0We still have 19 spare bits in ->i_flags and at least 22 in= ->i_state. > Do we need to bother with new field at all? =A0->i_state is unsigned = long... Do we *need* it? No. But it's often in the next cache-line. It would be beautiful to put the bits right next to i_mode, and basically make a lot of the common operations just touch those four bytes for doing the S_ISDIR tests and the "can I use generic_permission()" tests etc. And the whole point of that is to make for a smaller cacheline footprint (and admittedly also the few cycles to avoid the dereference - and that you'd get from using i_state). Linus -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html