From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030949AbXD1C14 (ORCPT ); Fri, 27 Apr 2007 22:27:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030952AbXD1C14 (ORCPT ); Fri, 27 Apr 2007 22:27:56 -0400 Received: from smtp107.mail.mud.yahoo.com ([209.191.85.217]:32072 "HELO smtp107.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1030949AbXD1C1z (ORCPT ); Fri, 27 Apr 2007 22:27:55 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=6WhlHFw2lJsyZo2ETMbykG3h5jD1Yt6MnH6xb4YYhgriekziEfbXHgW0Et/V8GALh2gzeCfxLcQRztJYw7U4bxy6OLMW/QKAiLj85IoMxmFyVzSavbicC9eyoh6jLUAVpoH9Ckn7RHQzgmNx06b69EUi0bRZ37Vyzb0fRmpgl+Y= ; X-YMail-OSG: psjpxu4VM1maeXomKq0k6.GJEvLNrqJ4LDGMCL8x3Cko4aBK4ltH79ffr0FaWjruc_p03vXoew-- Message-ID: <4632B121.3030005@yahoo.com.au> Date: Sat, 28 Apr 2007 12:27:45 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Christoph Hellwig CC: Christoph Lameter , Paul Mackerras , Andrew Morton , David Chinner , linux-kernel@vger.kernel.org, Mel Gorman , William Lee Irwin III , Jens Axboe , Badari Pulavarty , Maxim Levitsky Subject: Re: [00/17] Large Blocksize Support V3 References: <20070427022731.GF65285596@melbourne.sgi.com> <20070426195357.597ffd7e.akpm@linux-foundation.org> <20070427042046.GI65285596@melbourne.sgi.com> <20070426221528.655d79cb.akpm@linux-foundation.org> <20070426235542.bad7035a.akpm@linux-foundation.org> <17969.55533.59287.509889@cargo.ozlabs.ibm.com> <4631E173.7000204@yahoo.com.au> <4631EBC8.4060003@yahoo.com.au> <20070427133947.GB4152@infradead.org> In-Reply-To: <20070427133947.GB4152@infradead.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Christoph Hellwig wrote: > On Fri, Apr 27, 2007 at 10:25:44PM +1000, Nick Piggin wrote: > >>Linus's favourite jokes about powerpc mmu being crippled forever, aside ;) > > > Different mmu. The desktop 32bit mmu Linus refered to has almost nothing > in common with the mmu on 64bit systems. Well I wasn't trying to make a point there so it isn't a big deal... but he has known to say the 64-bit hash table is insane or broken. If he's since recanted, I'd be interested to read the post :) >>>Right this could help but it is not addressing the basic requirement for >>>devices that need large contiguuos chunks of memory for I/O. >> >>Did you read the last paragraph? Or anything Andrew's been writing? >> >> "After that, I'd find it amusing if HBAs worth thousands of $ have >> trouble looking up sglists at the relatively glacial pace that IO >> requires, and/or can't spare a few more K for reasonable sglist >> sizes, but if that is really the case, then we could use iommus >> and/or just attempt to put physically contiguous pages in pagecache, >> rather than require it." > > > Real highend HBAs don't have that problem. But for example aacraid > which is very common on mid-end servers is a _lot_ faster when it > gets continous memory. Some benchmark was 10 or more percent faster > on windows due to this. And that wasn't due to the 128 sg limit? I guess 10% isn't a small amount. Though it would be nice to have before/after numbers for Linux. And, like Andrew was saying, we could just _attempt_ to put contiguous pages in pagecache rather than _require_ it. Which is still robust under fragmentation, and benefits everyone, not just files with a large pagecache size. -- SUSE Labs, Novell Inc.