From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH for-next V2 0/9] Add completion timestamping support Date: Mon, 1 Jun 2015 11:29:29 -0600 Message-ID: <20150601172929.GA17715@obsidianresearch.com> References: <1433074457-26437-1-git-send-email-ogerlitz@mellanox.com> <1433098827.114391.179.camel@redhat.com> <1433157904.114391.188.camel@redhat.com> <20150601164322.GA14391@obsidianresearch.com> <1433178057.114391.208.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1433178057.114391.208.camel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Doug Ledford Cc: Matan Barak , Or Gerlitz , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Amir Vadai , Tal Alon List-Id: linux-rdma@vger.kernel.org On Mon, Jun 01, 2015 at 01:00:57PM -0400, Doug Ledford wrote: > > case for this feature, generalizing too much may destroy the > > performance that is valuable here. > I'm not convinced of that. Steve has already spoke up about the > timestamps available in cxgb4. Those are very different and yet still > highly valuable to someone investigating performance of their RDMA > application. ? cxgb4 looks nearly identical to me. There is only one HW time stamp 'cqe_sge_ts', which occurs at some point in the flow, and is written the CQE. The current cycle counter can be read from SGE_TIMESTAMP_LO registers. Same as mlx4, really. The rest is just bookkeeping and logging that doesn't require special verbs support for an app to implement. 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