From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 13 May 2008 10:32:38 -0500 From: Robin Holt Subject: Re: [PATCH 08 of 11] anon-vma-rwsem Message-ID: <20080513153238.GL19717@sgi.com> References: <6b384bb988786aa78ef0.1210170958@duo.random> <20080508003838.GA9878@sgi.com> <200805132206.47655.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200805132206.47655.nickpiggin@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Robin Holt , Linus Torvalds , Andrea Arcangeli , Andrew Morton , Christoph Lameter , Jack Steiner , Nick Piggin , Peter Zijlstra , kvm-devel@lists.sourceforge.net, Kanoj Sarcar , Roland Dreier , Steve Wise , linux-kernel@vger.kernel.org, Avi Kivity , linux-mm@kvack.org, general@lists.openfabrics.org, Hugh Dickins , Rusty Russell , Anthony Liguori , Chris Wright , Marcelo Tosatti , Eric Dumazet , "Paul E. McKenney" List-ID: On Tue, May 13, 2008 at 10:06:44PM +1000, Nick Piggin wrote: > On Thursday 08 May 2008 10:38, Robin Holt wrote: > > In order to invalidate the remote page table entries, we need to message > > (uses XPC) to the remote side. The remote side needs to acquire the > > importing process's mmap_sem and call zap_page_range(). Between the > > messaging and the acquiring a sleeping lock, I would argue this will > > require sleeping locks in the path prior to the mmu_notifier invalidate_* > > callouts(). > > Why do you need to take mmap_sem in order to shoot down pagetables of > the process? It would be nice if this can just be done without > sleeping. We are trying to shoot down page tables of a different process running on a different instance of Linux running on Numa-link connected portions of the same machine. The messaging is clearly going to require sleeping. Are you suggesting we need to rework XPC communications to not require sleeping? I think that is going to be impossible since the transfer engine requires a sleeping context. Additionally, the call to zap_page_range expects to have the mmap_sem held. I suppose we could use something other than zap_page_range and atomically clear the process page tables. Doing that will not alleviate the need to sleep for the messaging to the other partitions. Thanks, Robin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org