From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: 2x difference between multi-thread and multi-process for same number of CTXs Date: Wed, 24 Jan 2018 10:08:30 -0700 Message-ID: <20180124170830.GD16845@ziepe.ca> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Rohit Zambre Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Wed, Jan 24, 2018 at 10:22:53AM -0600, Rohit Zambre wrote: > (1) First, is this a surprising result or is the 2x difference > actually expected behavior? Maybe, there are lots of locks in one process, for instance glibc's malloc has locking - so any memory allocation anywhere in the applications processing path will cause lock contention. The issue may have nothing to do with RDMA. There is also some locking inside the userspace mlx5 driver that may contend depending on how your process has set things up. The entire send path is in user space so there is no kernel component here. 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