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[67.180.167.114]) by smtp.googlemail.com with ESMTPSA id g77sm11678641pfk.49.2018.01.24.19.55.44 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 24 Jan 2018 19:55:44 -0800 (PST) Message-ID: <1516852543.3715.43.camel@gmail.com> Subject: Re: [PATCH] net/mlx4_en: ensure rx_desc updating reaches HW before prod db updating From: Eric Dumazet To: "jianchao.wang" , Tariq Toukan , Jason Gunthorpe Cc: junxiao.bi@oracle.com, netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, Saeed Mahameed Date: Wed, 24 Jan 2018 19:55:43 -0800 In-Reply-To: <532b4d71-e2eb-35f3-894e-1c3288e7bc3f@oracle.com> References: <1515728542-3060-1-git-send-email-jianchao.w.wang@oracle.com> <20180112163247.GB15974@ziepe.ca> <1515775567.131759.42.camel@gmail.com> <53b1ac4d-a294-eb98-149e-65d7954243da@oracle.com> <1516376999.3606.39.camel@gmail.com> <339a7156-9ef1-1f3c-30b8-3cc3558d124e@mellanox.com> <532b4d71-e2eb-35f3-894e-1c3288e7bc3f@oracle.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2018-01-25 at 11:27 +0800, jianchao.wang wrote: > Hi Tariq > > On 01/22/2018 10:12 AM, jianchao.wang wrote: > > > > On 19/01/2018 5:49 PM, Eric Dumazet wrote: > > > > > On Fri, 2018-01-19 at 23:16 +0800, jianchao.wang wrote: > > > > > > Hi Tariq > > > > > > > > > > > > Very sad that the crash was reproduced again after applied the patch. > > > > > > Memory barriers vary for different Archs, can you please share more details regarding arch and repro steps? > > The hardware is HP ProLiant DL380 Gen9/ProLiant DL380 Gen9, BIOS P89 12/27/2015 > > The xen is installed. The crash occurred in DOM0. > > Regarding to the repro steps, it is a customer's test which does heavy disk I/O over NFS storage without any guest. > > > > What is the finial suggestion on this ? > If use wmb there, is the performance pulled down ? Since https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=dad42c3038a59d27fced28ee4ec1d4a891b28155 we batch allocations, so mlx4_en_refill_rx_buffers() is not called that often. I doubt the additional wmb() will have serious impact there.