From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] ummunotify: Userspace support for MMU notifications Date: Wed, 14 Apr 2010 11:52:28 +0300 Message-ID: <20100414085228.GL23554@redhat.com> References: <1271053337-7121-1-git-send-email-ebmunson@us.ibm.com> <20100412160359.1d9074dc.akpm@linux-foundation.org> <20100412235937.GF15629@obsidianresearch.com> <3251DDDA-D705-4B1E-9595-9C24709EF146@Sun.com> <1271181774.4807.1868.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1271181774.4807.1868.camel@twins> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Peter Zijlstra Cc: Roland Dreier , =?utf-8?B?SMOla29u?= Bugge , Jason Gunthorpe , Andrew Morton , Eric B Munson , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, rolandd-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org, pavel-+ZI9xUNit7I@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, jsquyres-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Tue, Apr 13, 2010 at 08:02:54PM +0200, Peter Zijlstra wrote: > On Tue, 2010-04-13 at 10:57 -0700, Roland Dreier wrote: > > Are those system calls the only possible way that virtual to physical > > mappings can change? Can't page migration or something like that > > potentially affect things? And even if you did have hooks into every > > system call that mattered (keep in mind that relying on glibc is not > > enough, since an MPI application may not use glibc) would decoding them > > and figuring out what happened really be preferable to a single event > > type that tells you exactly what address range was affected? > > Yeah, virtual<->physical maps can change through swapping, page > migration, memory compaction, huge-page aggregation (the latter two not > yet being upstream). > > Even mlock() doesn't pin virtual<->physical maps. Pages registered for RDMA are GUPed so no method above should touch them. Fork+cow or unmap/map on the other hand can change virtual<->physical maps. GUPed pages are still GUPed, but they are no longer mapped into process' virtual address space. MPI copes with Fork+cow by marking registered memory as MADV_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