From mboxrd@z Thu Jan 1 00:00:00 1970 From: Doug Ledford Subject: Re: [PATCH for-next 09/10] IB/mlx4: Add timestamp_mask and hca_core_clock to query_device Date: Fri, 29 May 2015 13:14:48 -0400 Message-ID: <1432919688.114391.116.camel@redhat.com> References: <20150527222108.GA7855@obsidianresearch.com> <5566BDE4.50709@mellanox.com> <20150528162416.GA6515@obsidianresearch.com> <20150528175043.GA10966@obsidianresearch.com> <20150528195034.GA11182@obsidianresearch.com> <20150528204749.GA12780@obsidianresearch.com> <1432918170.114391.104.camel@redhat.com> <1828884A29C6694DAF28B7E6B8A82373A8FE2126@ORSMSX109.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-WUd2O41BTp/a3i67XLRW" Return-path: In-Reply-To: <1828884A29C6694DAF28B7E6B8A82373A8FE2126-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Hefty, Sean" Cc: Christoph Lameter , Jason Gunthorpe , Or Gerlitz , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Amir Vadai , Tal Alon , Matan Barak , Yann Droneaud List-Id: linux-rdma@vger.kernel.org --=-WUd2O41BTp/a3i67XLRW Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2015-05-29 at 17:09 +0000, Hefty, Sean wrote: > > Now, as a general rule, I would call timestamps general. They should b= e > > added in a fashion that anyone can implement. They should also be well > > defined. Sean's questions raise a very valid point. Exactly what is > > being timestamped, and do we care about different timestamp options? I= s > > it completion of message, start of message, transfer from HCA to main > > system memory completion, etc. The 00/10 header to this patch series > > was probably answering Sean's question, but just based on the name of > > the TIMESTAMP flag to the CQ creation attr struct it isn't clear that > > this is the case. >=20 > I didn't see the information that I was looking for in the patch header t= o this series. As Jason pointed out, the use case is lacking. >=20 > IMO, it could make just as much sense to associate/enable time stamping w= ith the QP as with the CQ, or even make it configurable per operation or op= eration type. >=20 > If Christoph has a clear use case and wants to go to the 'bare metal', th= en a vendor specific option seems ideal. At least until there are other im= plementations or the driving use case is clearer. The use case is clear IMO. It's for financial trading software. I don't think they really care about details like whether it's the start or end packet, or completion, or whatever. They need a tie breaker between when they have two different buy or sell orders on the same lot of stock. Any deterministic timing/ordering method will do as long as they consistently apply it I think. And the faster and lower overhead the process, the better. He doesn't really want a timestamp, he merely wants a sequence ordering. But a timestamp is what they are using to get him what he needs. Is that a fair guess Christoph? --=20 Doug Ledford GPG KeyID: 0E572FDD --=-WUd2O41BTp/a3i67XLRW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABCAAGBQJVaJ6IAAoJELgmozMOVy/dYPgQAJl+NRhy/PpaHP2iqrSrowNo w67kUqV51pLwEMF477AU8BA7UBP/RchCPim/dQSpyR2JubNveX5QtWnH1kLKtB1O G/8PDpx+kNOOEFUzi+zox7XqzA2eYdXVXQzQd7wVbnrGESgHrLKcOjJQv5UMaRFT nJwDWlFbSlX+3Rl8Oe3XpEp69/EGVlAQ6uNQl12jzPHnowJqQC4cMca9C0eKYjs4 W2PIYggBTdLfpa3HERdH9Vix0FQd/jpe+kpZ6d3gB2l8F8fEHcW0n1gXPY5eU5QD C2XITmSBixZwzQRrr4jGTK7GKF+efTE1mkpeepJ74dqNbMcykNxo3cirNg4IfZt+ M7XT+eP0C53TWngb8ixD1E/PHWdCP2M3BMJiUqVY1IMJot16SB+bwII83HZOIHFF aGZwJSueQP3OVny7PMJrSVgDFIAk8JNPVzVjzAh65TZLoIAzqn72Uik536I2gofC TzOtk58IWEohCOoWYTU84lEBoNlEnLJPHa9E1CphOe7JGxg/5dUnA3CjDnJLw8Xw DNgrAKvezf/9BxzuwfJdlIsrYXPs8z2cwStyDQ9SE0V2hZBZOkrtRgUBIHUTix0m s+1ehlB9dVhLWJIntMxAXTwOoXb3NnwRRxm/peckfiMA5yGkN3dHHsPOAd/PKCQH 1IIppkdP22Rr0I48fe8O =Zneo -----END PGP SIGNATURE----- --=-WUd2O41BTp/a3i67XLRW-- -- 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