From mboxrd@z Thu Jan 1 00:00:00 1970 From: tedheadster Subject: Re: [PATCH] x86: enable swiotlb for > 4GiG ram on 32-bit kernels Date: Tue, 16 Oct 2018 09:11:09 -0400 Message-ID: References: <20181014075208.2715-1-hch@lst.de> Reply-To: whiteheadm-HInyCGIudOg@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181014075208.2715-1-hch-jcswGhMUV9g@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Christoph Hellwig Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, konrad.wilk-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org List-Id: iommu@lists.linux-foundation.org On Sun, Oct 14, 2018 at 3:52 AM Christoph Hellwig wrote: > > We already build the swiotlb code for 32b-t kernels with PAE support, > but the code to actually use swiotlb has only been enabled for 64-bit > kernel for an unknown reason. > > Before Linux 4.18 we papers over this fact because the networking code, > the scsi layer and some random block drivers implenented their own > bounce buffering scheme. > > Fixes: 21e07dba ("scsi: reduce use of block bounce buffers") > Fixes: ab74cfeb ("net: remove the PCI_DMA_BUS_IS_PHYS check in illegal_highdma") > Reported-by: tedheadster > Tested-by: tedheadster > --- > Christoph, this fix has causes performance to decrease dramatically. Kernel builds that used to take 10-15 minutes are now taking 45-60 minutes on the same machine. - Matthew Whitehead