Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751993AbdHDIwm (ORCPT ); Fri, 4 Aug 2017 04:52:42 -0400 Received: from mga11.intel.com ([192.55.52.93]:1156 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751293AbdHDIwj (ORCPT ); Fri, 4 Aug 2017 04:52:39 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,320,1498546800"; d="scan'208";a="115550373" Message-ID: <5984367A.3030809@intel.com> Date: Fri, 04 Aug 2017 16:55:22 +0800 From: Wei Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Michal Hocko CC: "Michael S. Tsirkin" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "kvm@vger.kernel.org" , "linux-mm@kvack.org" , "mawilcox@microsoft.com" , "akpm@linux-foundation.org" , "virtio-dev@lists.oasis-open.org" , "david@redhat.com" , "cornelia.huck@de.ibm.com" , "mgorman@techsingularity.net" , "aarcange@redhat.com" , "amit.shah@redhat.com" , "pbonzini@redhat.com" , "liliang.opensource@gmail.com" , "yang.zhang.wz@gmail.com" , "quan.xu@aliyun.com" Subject: Re: [PATCH v13 4/5] mm: support reporting free page blocks References: <59830897.2060203@intel.com> <20170803112831.GN12521@dhcp22.suse.cz> <5983130E.2070806@intel.com> <20170803124106.GR12521@dhcp22.suse.cz> <59832265.1040805@intel.com> <20170803135047.GV12521@dhcp22.suse.cz> <286AC319A985734F985F78AFA26841F73928C971@shsmsx102.ccr.corp.intel.com> <20170804000043-mutt-send-email-mst@kernel.org> <20170804075337.GC26029@dhcp22.suse.cz> <59842D1C.5020608@intel.com> <20170804082423.GG26029@dhcp22.suse.cz> In-Reply-To: <20170804082423.GG26029@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 980 Lines: 23 On 08/04/2017 04:24 PM, Michal Hocko wrote: > >> For our use case, the callback just puts the reported page >> block to the ring, then returns. If the ring is full as the host >> is busy, then I think it should skip this one, and just return. >> Because: >> A. This is an optimization feature, losing a couple of free >> pages to report isn't that important; >> B. In reality, I think it's uncommon to see this ring getting >> full (I didn't observe ring full in the tests), since the host >> (consumer) is notified to take out the page block right >> after it is added. > I thought you only updated a pre allocated bitmat... Anyway, I cannot > comment on this part much as I am not familiar with your usecase. > Actually the bitmap is in the hypervisor (host). The callback puts the (pfn,size) on a ring which is shared with the hypervisor, then the hypervisor takes that info from the ring and updates that bitmap. Best, Wei