From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] IB/ipoib: move back the IB LL address into the hard header Date: Thu, 13 Oct 2016 10:24:32 -0400 (EDT) Message-ID: <20161013.102432.1450901395774429343.davem@davemloft.net> References: <1dbd83dfe7f435eecc5bc460e901b47758280f30.1476206016.git.pabeni@redhat.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org Return-path: In-Reply-To: <1dbd83dfe7f435eecc5bc460e901b47758280f30.1476206016.git.pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org From: Paolo Abeni Date: Tue, 11 Oct 2016 19:15:44 +0200 > After the commit 9207f9d45b0a ("net: preserve IP control block > during GSO segmentation"), the GSO CB and the IPoIB CB conflict. > That destroy the IPoIB address information cached there, > causing a severe performance regression, as better described here: > > http://marc.info/?l=linux-kernel&m=146787279825501&w=2 > > This change moves the data cached by the IPoIB driver from the > skb control lock into the IPoIB hard header, as done before > the commit 936d7de3d736 ("IPoIB: Stop lying about hard_header_len > and use skb->cb to stash LL addresses"). > In order to avoid GRO issue, on packet reception, the IPoIB driver > stash into the skb a dummy pseudo header, so that the received > packets have actually a hard header matching the declared length. > Also the connected mode maximum mtu is reduced by 16 bytes to > cope with the increased hard header len. > > After this commit, IPoIB performances are back to pre-regression > value. > > Fixes: 9207f9d45b0a ("net: preserve IP control block during GSO segmentation") > Signed-off-by: Paolo Abeni Not providing an accurate hard_header_len causes many problems. In fact we recently fixed the mlxsw driver to stop doing this. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html