From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [00/41] Large Blocksize Support V7 (adds memmap support) Date: Sun, 16 Sep 2007 11:44:09 -0700 (PDT) Message-ID: References: <20070911060349.993975297@sgi.com> <200709110452.20363.nickpiggin@yahoo.com.au> <20070911121225.GE13132@lazybastard.org> <20070915014449.4f9cdb51.akpm@linux-foundation.org> <87ir6c3z2l.fsf@informatik.uni-tuebingen.de> <20070915155100.GA21861@v2.random> <87tzpvy9cb.fsf@informatik.uni-tuebingen.de> <20070915223032.GA6708@v2.random> <20070916174657.GA2393@lazybastard.org> <20070916182136.GC2393@lazybastard.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=iso-8859-15 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Andrea Arcangeli , Goswin von Brederlow , Andrew Morton , Nick Piggin , Christoph Lameter , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , Mel Gorman , William Lee Irwin III , David Chinner , Jens Axboe , Badari Pulavarty , Maxim Levitsky , Fengguang Wu , swin wang , totty.lu@gmail.com, hugh@veritas.com To: =?iso-8859-15?Q?J=F6rn_Engel?= Return-path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:56607 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752186AbXIPSpN (ORCPT ); Sun, 16 Sep 2007 14:45:13 -0400 In-Reply-To: <20070916182136.GC2393@lazybastard.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Sun, 16 Sep 2007, J=F6rn Engel wrote: >=20 > My approach is to have one for mount points and ramfs/tmpfs/sysfs/etc= =2E > which are pinned for their entire lifetime and another for regular > files/inodes. One could take a three-way approach and have > always-pinned, often-pinned and rarely-pinned. >=20 > We won't get never-pinned that way. That sounds pretty good. The problem, of course, is that most of the ti= me,=20 the actual dentry allocation itself is done before you really know whic= h=20 case the dentry will be in, and the natural place for actually giving t= he=20 dentry lifetime hint is *not* at "d_alloc()", but when we "instantiate"= =20 it with d_add() or d_instantiate(). But it turns out that most of the filesystems we care about already use= a=20 special case of "d_add()" that *already* replaces the dentry with anoth= er=20 one in some cases: "d_splice_alias()". So I bet that if we just taught "d_splice_alias()" to look at the inode= ,=20 and based on the inode just re-allocate the dentry to some other slab=20 cache, we'd already handle a lot of the cases! And yes, you'd end up with the reallocation overhead quite often, but a= t=20 least it would now happen only when filling in a dentry, not in the=20 (*much* more critical) cached lookup path. 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