From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH] ib_ipoib: Scatter-Gather support in connected mode Date: Mon, 23 Mar 2015 11:17:49 -0600 Message-ID: <20150323171749.GA3580@obsidianresearch.com> References: <1422357682-8934-1-git-send-email-yuval.shaia@oracle.com> <1422444987.3133.81.camel@opteya.com> <20150201070941.GA4778@yuval-lab> <20150315151616.GA3546@yuval-lab> <20150322092149.GA5229@yuval-lab> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20150322092149.GA5229@yuval-lab> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Yuval Shaia Cc: roland-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Sun, Mar 22, 2015 at 11:21:50AM +0200, Yuval Shaia wrote: > On Sun, Mar 15, 2015 at 05:16:16PM +0200, Yuval Shaia wrote: > > Hi, > > I didn't got any further comments on this one. > > Any idea why SG in CM is un-welcome? > By mistake I sent a private mail only. > Cc: Roland Dreier > Cc: Sean Hefty > Cc: Hal Rosenstock > > Your advice would be very appreciated. I haven't looked in detail at the patch, but in principle, using S/G when ever possible should be the default, even if this creates a performance regression. It is well known that high order allocations are problematic in Linux and should be avoided, and I also have seen systems blow up because of high order IPoIB allocations. That said, there may be cases where S/G is not possible, you should try and get Mellanox to comment if all their offloads work on all their cards when S/G is used. Work may be required to resolve any of these constraints. I'd like to belive there is some reason why we've been doing high order allocations for so many years. FWIW, I would probably choose to default S/G over any other offload acceleration. Jason -- 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