From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v2 0/4] vhost: add missing barriers, move prefetching Date: Wed, 19 Dec 2018 10:50:42 -0500 Message-ID: <20181219104947-mutt-send-email-mst@kernel.org> References: <20181219082113.24455-1-maxime.coquelin@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dev@dpdk.org, i.maximets@samsung.com, tiwei.bie@intel.com, zhihong.wang@intel.com, jasowang@redhat.com, stable@dpdk.org To: Maxime Coquelin Return-path: Content-Disposition: inline In-Reply-To: <20181219082113.24455-1-maxime.coquelin@redhat.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Wed, Dec 19, 2018 at 09:21:09AM +0100, Maxime Coquelin wrote: > This series adds missing read barriers after reading avail index > for split ring and desc flags for packed ring. > > Also, it turns out that some descriptors prefetching are either > badly placed, or useless, last part of the series fixes that. > > With the series applied, I get between 0 and 4% gain depending > on the benchmark (testpmd txonly/rxonly/io). > > Thanks to Jason for reporting the missing read barriers. Acked-by: Michael S. Tsirkin But I wonder what effect this has on ARM where RMB isn't a NOP. Ilya do you happen to have any data? > Changes since v1: > ================= > - Drop volatile removal patch (Ilya) > - Improve commit messages for RMB patches (Ilya) > > Maxime Coquelin (4): > vhost: enforce avail index and desc read ordering > vhost: enforce desc flags and content read ordering > vhost: prefetch descriptor after the read barrier > vhost: remove useless prefetch for packed ring descriptor > > lib/librte_vhost/virtio_net.c | 27 ++++++++++++++++++++++----- > 1 file changed, 22 insertions(+), 5 deletions(-) > > -- > 2.17.2