From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [GIT PULL] please pull ummunotify Date: Fri, 11 Sep 2009 19:42:47 +0300 Message-ID: <20090911164247.GA6736@redhat.com> References: <20090911145036.DB65.A69D9226@jp.fujitsu.com> <20090911150552.DB68.A69D9226@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20090911150552.DB68.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: KOSAKI Motohiro Cc: Roland Dreier , torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, jsquyres-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, general-ZwoEplunGu1OwGhvXhtEPSCwEArCW2h5@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Fri, Sep 11, 2009 at 03:11:36PM +0900, KOSAKI Motohiro wrote: > Hi > > Thank you explanation. > > > > > > Can I this version already solved fork() + COW issue? if so, could you > > > please explain what happen at fork. Obviously RDMA point to either parent > > > or child page, not both. but Corrent COW rule is, first touch process > > > get copyed page and other process still own original page. I think it's > > > unpecected behavior form RDMA. > > > > No, ummunotify doesn't really help that much with fork() + COW. If a > > parent forks and then touches pages that are actively in use for RDMA, > > then of course they get COWed and RDMA goes to the wrong memory (from > > the point of view of the parent). > > So, Can we assume OpenMPI user process doesn't such thing? > > Parhaps, madvise(DONTFORK) or vfork() avoid this issue. but I'm not > sure all program in the world do that. > MPI (or is it libibverbs?) marks all registered memory as DONTFORK. -- Gleb. -- 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