From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx141.postini.com [74.125.245.141]) by kanga.kvack.org (Postfix) with SMTP id 66CE56B005D for ; Wed, 5 Sep 2012 08:55:36 -0400 (EDT) Message-ID: <50474BBB.2070509@redhat.com> Date: Wed, 05 Sep 2012 15:55:23 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [PATCH V1 0/2] Enable clients to schedule in mmu_notifier methods References: <1346748081-1652-1-git-send-email-haggaie@mellanox.com> <20120904150615.f6c1a618.akpm@linux-foundation.org> In-Reply-To: <20120904150615.f6c1a618.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Haggai Eran , linux-mm@kvack.org, Andrea Arcangeli , Peter Zijlstra , Xiao Guangrong , Shachar Raindel , Sagi Grimberg , Or Gerlitz On 09/05/2012 01:06 AM, Andrew Morton wrote: > On Tue, 4 Sep 2012 11:41:19 +0300 > Haggai Eran wrote: > >> > This patchset is a preliminary step towards on-demand paging design to be >> > added to the Infiniband stack. > > The above sentence is the most important part of the patchset. Because > it answers the question "ytf is Haggai sending this stuff at me". > > I'm unsure if the patchset adds runtime overhead but it does add > maintenance overhead (perhaps we can reduce this - see later emails). > So we need to take a close look at what we're getting in return for > that overhead, please. > > Exactly why do we want on-demand paging for Infiniband? Why should > anyone care? What problems are users currently experiencing? How many > users and how serious are the problems and what if any workarounds are > available? > > Is there any prospect that any other subsystems will utilise these > infrastructural changes? If so, which and how, etc? > > > > IOW, sell this code to us! kvm may be a buyer. kvm::mmu_lock, which serializes guest page faults, also protects long operations such as destroying large ranges. It would be good to convert it into a spinlock, but as it is used inside mmu notifiers, this cannot be done. (there are alternatives, such as keeping the spinlock and using a generation counter to do the teardown in O(1), which is what the "may" is doing up there). -- error compiling committee.c: too many arguments to function -- 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