From mboxrd@z Thu Jan 1 00:00:00 1970 From: Or Gerlitz Subject: Re: rdma_lat whos Date: Wed, 24 Nov 2010 17:00:51 +0200 Message-ID: <4CED28A3.9070907@Voltaire.com> References: <4CE3B455.4080003@Voltaire.com> <4CE3BCE3.7090107@Voltaire.com> <4CE50190.3080707@dev.mellanox.co.il> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4CE50190.3080707-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ido Shamai , Jack Morgenstein Cc: linux-rdma , Moni Shoua , Sean Hefty , Alex Rosenbaum List-Id: linux-rdma@vger.kernel.org Ido Shamai wrote: > I will check the issue now. Thinking a little further on this and talking with some colleagues, a question was made, whether the issue can be related to IB credits/starvation and/or protocol/interoperability with switches. In an attempt to eliminate that, I repeated the test, this time in a loopback manner, e.g used ib_send_lat once with mtu=256 and once with mtu=2048 with both client/server running on the same node/hca - same result, the mtu=256 produces much better latency for large messages, e.g 1k and onward, for example for msg size=8k the latency is ~7us with mtu=256 and ~9us with mtu=2k I recalled that on the 2nd generation HCA (tavor), if mtu=2048 is used, the bandwidth is severely damaged (hence the ofed tavor quirk and friends) can this problem which I see on the 4th generation HCA, be somehow related? Or. -- 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