From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758807AbYDAL1o (ORCPT ); Tue, 1 Apr 2008 07:27:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756865AbYDAL1f (ORCPT ); Tue, 1 Apr 2008 07:27:35 -0400 Received: from mail.windriver.com ([147.11.1.11]:60063 "EHLO mail.wrs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756710AbYDAL1e (ORCPT ); Tue, 1 Apr 2008 07:27:34 -0400 Message-ID: <47F21C06.7070809@windriver.com> Date: Tue, 01 Apr 2008 19:27:02 +0800 From: yshi User-Agent: Thunderbird 2.0.0.12 (X11/20080213) MIME-Version: 1.0 To: Andrea Arcangeli CC: Andrew Morton , linux-kernel@vger.kernel.org, kvm-devel@lists.sourceforge.net, Jens Axboe Subject: Re: regression breaks lowmem reserved RAM References: <20080328194909.GA10617@duo.random> <20080401105331.GH12427@duo.random> In-Reply-To: <20080401105331.GH12427@duo.random> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 01 Apr 2008 11:26:50.0166 (UTC) FILETIME=[473A4D60:01C893EB] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andrea, This patch works well on my machine. Thanks. Best Regards, Yang Andrea Arcangeli ??: > Looking a bit closer into this regression the reason this can't be > right is that dma_addr common default is BLK_BOUNCE_HIGH and most > machines have less than 4G. So if you do: > > if (b_pfn <= (min_t(u64, 0xffffffff, BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) > dma = 1 > > that will translate to: > > if (BLK_BOUNCE_HIGH <= BLK_BOUNCE_HIGH) > dma = 1 > > So for 99% of hardware this will trigger unnecessary GFP_DMA > allocations and isa pooling operations. > > Also note how the 32bit code still does b_pfn < blk_max_low_pfn. > > I guess this is what you were looking after. I didn't verify but as > far as I can tell, this will stop the regression with isa dma > operations at boot for 99% of blkdev/memory combinations out there and > I guess this fixes the setups with >4G of ram and 32bit pci cards as > well (this also retains symmetry with the 32bit code). > > Signed-off-by: Andrea Arcangeli > > diff --git a/block/blk-settings.c b/block/blk-settings.c > index 1344a0e..5713f7e 100644 > --- a/block/blk-settings.c > +++ b/block/blk-settings.c > @@ -140,7 +140,7 @@ void blk_queue_bounce_limit(struct request_queue *q, u64 dma_addr) > /* Assume anything <= 4GB can be handled by IOMMU. > Actually some IOMMUs can handle everything, but I don't > know of a way to test this here. */ > - if (b_pfn <= (min_t(u64, 0xffffffff, BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) > + if (b_pfn < (min_t(u64, 0x100000000UL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) > dma = 1; > q->bounce_pfn = max_low_pfn; > #else > >