From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751679AbeAYWl1 (ORCPT ); Thu, 25 Jan 2018 17:41:27 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:46444 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751432AbeAYWl0 (ORCPT ); Thu, 25 Jan 2018 17:41:26 -0500 Date: Thu, 25 Jan 2018 14:41:24 -0800 From: Andrew Morton To: Wei Wang Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mst@redhat.com, mhocko@kernel.org, pbonzini@redhat.com, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu0@gmail.com, nilal@redhat.com, riel@redhat.com Subject: Re: [PATCH v25 1/2 RESEND] mm: support reporting free page blocks Message-Id: <20180125144124.7e9f6e2156b1b940b07aecfc@linux-foundation.org> In-Reply-To: <1516873107-34950-1-git-send-email-wei.w.wang@intel.com> References: <1516873107-34950-1-git-send-email-wei.w.wang@intel.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 25 Jan 2018 17:38:27 +0800 Wei Wang wrote: > This patch adds support to walk through the free page blocks in the > system and report them via a callback function. Some page blocks may > leave the free list after zone->lock is released, so it is the caller's > responsibility to either detect or prevent the use of such pages. > > One use example of this patch is to accelerate live migration by skipping > the transfer of free pages reported from the guest. A popular method used > by the hypervisor to track which part of memory is written during live > migration is to write-protect all the guest memory. So, those pages that > are reported as free pages but are written after the report function > returns will be captured by the hypervisor, and they will be added to the > next round of memory transfer. It would be useful if we had some quantitative testing results, so we can see the real-world benefits from this change?