From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751543AbeDEODn (ORCPT ); Thu, 5 Apr 2018 10:03:43 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:55848 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751195AbeDEODm (ORCPT ); Thu, 5 Apr 2018 10:03:42 -0400 Date: Thu, 5 Apr 2018 17:03:40 +0300 From: "Michael S. Tsirkin" To: "Wang, Wei W" 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" , "mhocko@kernel.org" , "akpm@linux-foundation.org" , "pbonzini@redhat.com" , "liliang.opensource@gmail.com" , "yang.zhang.wz@gmail.com" , "quan.xu0@gmail.com" , "nilal@redhat.com" , "riel@redhat.com" , "huangzhichao@huawei.com" Subject: Re: [PATCH v30 2/4] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Message-ID: <20180405170248-mutt-send-email-mst@kernel.org> References: <1522771805-78927-1-git-send-email-wei.w.wang@intel.com> <1522771805-78927-3-git-send-email-wei.w.wang@intel.com> <20180403214147-mutt-send-email-mst@kernel.org> <5AC43377.2070607@intel.com> <20180404155907-mutt-send-email-mst@kernel.org> <286AC319A985734F985F78AFA26841F7394A6E96@shsmsx102.ccr.corp.intel.com> <20180405040900-mutt-send-email-mst@kernel.org> <286AC319A985734F985F78AFA26841F7394A7F3B@shsmsx102.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <286AC319A985734F985F78AFA26841F7394A7F3B@shsmsx102.ccr.corp.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 05, 2018 at 02:05:03AM +0000, Wang, Wei W wrote: > On Thursday, April 5, 2018 9:12 AM, Michael S. Tsirkin wrote: > > On Thu, Apr 05, 2018 at 12:30:27AM +0000, Wang, Wei W wrote: > > > On Wednesday, April 4, 2018 10:08 PM, Michael S. Tsirkin wrote: > > > > On Wed, Apr 04, 2018 at 10:07:51AM +0800, Wei Wang wrote: > > > > > On 04/04/2018 02:47 AM, Michael S. Tsirkin wrote: > > > > > > On Wed, Apr 04, 2018 at 12:10:03AM +0800, Wei Wang wrote: > > > I'm afraid the driver couldn't be aware if the added hints are stale > > > or not, > > > > > > No - I mean that driver has code that compares two values and stops > > reporting. Can one of the values be stale? > > The driver compares "vb->cmd_id_use != vb->cmd_id_received" to decide if it needs to stop reporting hints, and cmd_id_received is what the driver reads from host (host notifies the driver to read for the latest value). If host sends a new cmd id, it will notify the guest to read again. I'm not sure how that could be a stale cmd id (or maybe I misunderstood your point here?) > > Best, > Wei The comparison is done in one thread, the update in another one. -- MST