From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roland Dreier Subject: Re: [PATCH 2/3] IB/srp: use IB_CQ_REPORT_MISSED_EVENTS to avoid missed CQ callbacks Date: Wed, 31 Mar 2010 11:57:15 -0700 Message-ID: References: <20100331175742.24522.17850.stgit@chromite.mv.qlogic.com> <20100331175752.24522.66519.stgit@chromite.mv.qlogic.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: (Bart Van Assche's message of "Wed, 31 Mar 2010 20:36:12 +0200") Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bart Van Assche Cc: Ralph Campbell , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org > Processing the flag IB_CQ_REPORT_MISSED_EVENTS causes several IB > drivers to lock and unlock a spinlock. Full-speed SRP I/O can cause > this operation to be invoked more than 100.000 times a second, so the > flag IB_CQ_REPORT_MISSED_EVENTS will have a small but measurable > impact on SRP I/O performance. It seems the only driver where that happens is ehca. But on the other hand, for mthca/mlx4 it avoids doing something like: cq event: request notify <-- CQ is not empty, another event queued drain CQ cq event: request notify drain already empty CQ ie the overhead saved here looks a lot more. -- Roland Dreier || For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/index.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