From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268699AbUH3Rgn (ORCPT ); Mon, 30 Aug 2004 13:36:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268646AbUH3RgB (ORCPT ); Mon, 30 Aug 2004 13:36:01 -0400 Received: from kinesis.swishmail.com ([209.10.110.86]:12551 "EHLO kinesis.swishmail.com") by vger.kernel.org with ESMTP id S268582AbUH3Rb5 (ORCPT ); Mon, 30 Aug 2004 13:31:57 -0400 Message-ID: <41336CB1.6030105@techsource.com> Date: Mon, 30 Aug 2004 14:06:41 -0400 From: Timothy Miller MIME-Version: 1.0 To: Timothy Miller CC: Andrew Morton , Jens Axboe , eric@cisu.net, kernel@kolivas.org, barryn@pobox.com, swsnyder@insightbb.com, linux-kernel@vger.kernel.org Subject: Re: HIGHMEM4G config for 1GB RAM on desktop? References: <200408021602.34320.swsnyder@insightbb.com> <410FA145.70701@kolivas.org> <20040804060625.GE10340@suse.de> <200408040614.30820.eric@cisu.net> <20040804130707.GN10340@suse.de> <20040804120633.4dca57b3.akpm@osdl.org> <411ABF85.2080200@techsource.com> In-Reply-To: <411ABF85.2080200@techsource.com> 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 Timothy Miller wrote: > > > Andrew Morton wrote: > >> >> >> The 896M/128M split has a bit of a problem now each zone has its own LRU: >> the size of the highmem zone is less than the amount of memory which is >> described by the default /proc/sys/vm/dirty_ratio. So it is easy to >> completely fill highmem with dirty pages. This causes a fairly large >> amount of writeback via vmscan.c's writepage(). This causes poor I/O >> submission patterns. This causes a simple large, linear `dd' write to >> run >> at only 50-70% of disk bandwidth. (This was 6-12 months ago - it >> might be >> a bit better now) >> > > > Hey, that rings a bell. I have a 3ware 7000-2 controller with two > WD1200JB drives in RAID1. I find that if I dd from the disk, I get > exactly the read throughput that is the max for the drives (47MB/sec). > However, if I do a WRITE test, the performance is miserable. > > I have been going back and forth with 3ware for months, and what's odd > is that my drives with my controller in any machine other than the > primary box get great write throughput, BUT on my main box with 1G of > RAM, I get MISERABLE write throughput. When I should be getting > 36MB/sec or faster, I get 8 to 12 MB/sec. > > Now, I have tried limiting the memory with a mem= boot option, but that > doesn't change the performance any. > Scratch all this. Even if I physically remove half the memory, I STILL get the performance problem.