From mboxrd@z Thu Jan 1 00:00:00 1970 From: "ira.weiny" Subject: Re: [PATCH] ib_ipoib: Scatter-Gather support in connected mode Date: Wed, 1 Apr 2015 13:17:19 -0400 Message-ID: <20150401171708.GA21266@phlsvsds.ph.intel.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> <20150323171749.GA3580@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20150323171749.GA3580-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Yuval Shaia , "roland-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" , "Hefty, Sean" , "hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org On Mon, Mar 23, 2015 at 11:17:49AM -0600, Jason Gunthorpe wrote: > 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. I concur with Jason's assessment. As Yann asked before: What hardware have you tested this on? Do you have any performance measurements? Or do you have a reproducer for some of the allocation issues which have been seen? I can't comment on how this may affect Mellanox Hardware but it seems like it will work fine with Qib hardware. Ira > > 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 -- 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