Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932315AbWHWCqq (ORCPT ); Tue, 22 Aug 2006 22:46:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932319AbWHWCqq (ORCPT ); Tue, 22 Aug 2006 22:46:46 -0400 Received: from wx-out-0506.google.com ([66.249.82.236]:7574 "EHLO wx-out-0506.google.com") by vger.kernel.org with ESMTP id S932315AbWHWCqp (ORCPT ); Tue, 22 Aug 2006 22:46:45 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:date:from:to:cc:subject:message-id:references:mime-version:content-type:content-disposition:in-reply-to:user-agent; b=e/aX+/qxI+hnFmd+joXcDqhFKK8XALKU+JCqxv9mAxsh2+hAJEq0e4Woq4Zky2jctRWlaz6Khm8g2HFHJ/SlC54y9MuuxW3Ssgo47A+OZwUWGQX8bFHY6VbCq/+B8AXUjvFlqsUD/VBLnweyD7qYSJRoOL8WoDp8YzsvTOtyIkU= Date: Tue, 22 Aug 2006 19:46:34 -0700 From: Clay Barnes To: Andrew Morton Cc: Jeff Mahoney , David Masover , Linus Torvalds , Linux Kernel Mailing List , ReiserFS List , Mike Benoit Subject: Re: [PATCH] reiserfs: eliminate minimum window size for bitmap searching Message-ID: <20060823024634.GK9112@HAL_5000D.tc.ph.cox.net> References: <44EB1484.2040502@suse.com> <44EB23D9.9000508@slaphack.com> <44EB28EC.50802@suse.com> <44EB684C.2090206@slaphack.com> <44EB7518.5010204@suse.com> <20060822171133.72692542.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060822171133.72692542.akpm@osdl.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1513 Lines: 33 On 17:11 Tue 22 Aug , Andrew Morton wrote: > > I can see that the bigalloc code as-is is pretty sad, but this is a scary > patch. It has the potential to cause people significant performance > problems way, way ahead in the future. > > For example, suppose userspace is growing two files concurrently. It could > be that the bigalloc code would cause one file's allocation cursor to > repeatedly jump far away from the second. ie: a beneficial side-effect. > Without bigalloc that side-effect is lost and the two files blocks end up > all intermingled. Perhaps I mis-recall, but shouldn't delayed writes (or something along those lines) cause a case where two files are being incrementally written rare? It seems that this case would only occur if two processes were writing two files in small chunks and calling fsync constantly (*cough* evolution column resizing bug *cough*), PLUS the two would have to have the same offset (or close) for the file writes. It seems that the risk of fragmentation is a lesser danger than the full system near lock-up caused by the old behavour. --Clay > > I don't know if that scenario is realistic, but I bet there are similar > accidental oddities which can occur as a result of this change. > > But what are they? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/