From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roland Dreier Subject: Re: [ofa-general] Re: [GIT PULL] please pull ummunotify Date: Fri, 11 Sep 2009 09:58:10 -0700 Message-ID: References: <20090911145036.DB65.A69D9226@jp.fujitsu.com> <4AA9EAF7.5010401@inria.fr> <20090911064019.GZ4973@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <20090911064019.GZ4973-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> (Jason Gunthorpe's message of "Fri, 11 Sep 2009 00:40:19 -0600") Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Brice Goglin , KOSAKI Motohiro , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, general-ZwoEplunGu1OwGhvXhtEPSCwEArCW2h5@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org List-Id: linux-rdma@vger.kernel.org > So.. What is the problem with fork? The semantics of what should > happen seem natural enough to me, the PD doesn't get copied to the > child, so the MR stays with the parent. COW events on the pinned > region must be resolved so that the physical page stays with the > process that has pinned it - the pin is logically released in the > child because the MR doesn't exist because the PD doesn't exist. This is getting away from the problem that ummunotify is solving, but handling a COW fault generated by the parent by doing the copy in the child seems like a pretty major, tricky change to make. The child may have forked 100 more times in the meantime, meaning we now have to change 101 memory maps ... the cost of page faults goes through the roof probably... - R. -- 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