From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roland Dreier Subject: Re: Ummunotify: progress at last! Date: Tue, 23 Mar 2010 22:59:42 -0700 Message-ID: References: <1CDB2AA4-A8DF-4169-943E-4EA190814596@cisco.com> <20100323165920.GH29129@obsidianresearch.com> <20100323172953.GI29129@obsidianresearch.com> <5F80899D-F989-4162-B050-7E4D6B389876@cisco.com> <20100323195251.GJ29129@obsidianresearch.com> <3B848E1F-C9B6-416A-9E6E-99604E71902A@cisco.com> <20100323201124.GK29129@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <20100323201124.GK29129-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> (Jason Gunthorpe's message of "Tue, 23 Mar 2010 14:11:24 -0600") Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Jeff Squyres , Linux RDMA List , Brad Benton List-Id: linux-rdma@vger.kernel.org > No, there is no mmap. Like this: > > u64 my_counter = 0; > > ibv_set_mmu_counter(verbs, &my_counter); > [..] > while (my_counter != last_my_counter) { > last_my_counter = my_counter; > ibv_get_mmu_notifications(verbs, ...); // <- I am a memory barrier as well > } > > The kernel 'syscall' ibv_set_mmu_counter would bind the given verbs to > the 8 byte counter you specified without having to the mmap thing. As > I understand it this is what perfevents does. > > Integrating with the verbs api avoids the need for another device > file. That is good. Eliminating poll() from the API can remove the > dedicated fd entirely. Within verbs I guess we could replace poll() > with something like a completion channel (??) if anyone cares. That is all definitely doable. I wonder if it's better to get rid of the dedicated fd though. After all, having the fd means a fancy app can do poll() or sigio or whatever internally. Being able to integrate into an fd-driven event loop seems like a pretty big thing to give up. Also, having a uverbs "syscall" that is exactly like read() seems a bit of a stretch, even within the ugliness that is the uverbs interface. (We love all our children, but sometimes we have to be realistic) - R. -- 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