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 11:15:36 -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> 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]:35020 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751773AbXIPSSd (ORCPT ); Sun, 16 Sep 2007 14:18:33 -0400 In-Reply-To: <20070916174657.GA2393@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 > I have been toying with the idea of having seperate caches for pinned > and movable dentries. Downside of such a patch would be the number o= f > memcpy() operations when moving dentries from one cache to the other. Totally inappropriate. I bet 99% of all "dentry_lookup()" calls involve turning the last dentr= y=20 from having a count of zero ("movable") to having a count of 1 ("pinned= "). So such an approach would fundamentally be broken. It would slow down a= ll=20 normal dentry lookups, since the *common* case for leaf dentries is tha= t=20 they have a zero count. So it's much better to do it on a "directory/file" basis, on the=20 assumption that files are *mostly* movable (or just freeable). The fact= =20 that they aren't always (ie while kept open etc), is likely statistical= ly=20 not all that important. 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