From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Wang Subject: Re: [Qemu-devel] [RFC] Buffers/caches in VirtIO Balloon driver stats Date: Fri, 15 Sep 2017 10:01:37 +0800 Message-ID: <59BB3481.7050909@intel.com> References: <20170827233033.7afa49b9@fiorina> <20170829095726.GL25960@stefanha-x1.localdomain> <59A557B1.7080704@intel.com> <20170912162947.130c2df2@fiorina> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: Stefan Hajnoczi , qemu-devel@nongnu.org, virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, "Michael S. Tsirkin" To: =?UTF-8?B?VG9tw6HFoSBHb2xlbWJpb3Zza8O9?= Return-path: Received: from mga03.intel.com ([134.134.136.65]:46499 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682AbdIOB6b (ORCPT ); Thu, 14 Sep 2017 21:58:31 -0400 In-Reply-To: <20170912162947.130c2df2@fiorina> Sender: kvm-owner@vger.kernel.org List-ID: On 09/12/2017 10:29 PM, Tomáš Golembiovský wrote: > On Tue, 29 Aug 2017 20:01:53 +0800 > Wei Wang wrote: > >> On 08/29/2017 05:57 PM, Stefan Hajnoczi wrote: >>> On Sun, Aug 27, 2017 at 11:30:33PM +0200, Tomáš Golembiovský wrote: >>>> Hi, >>> I have CCed the relevant mailing lists and people most recently involved >>> in virtio-balloon discussions. Hopefully this will help get the right >>> people to see your questions. >>> >>>> We'd like to include information about reclaimable memory into the >>>> statistics in VirtiO Balloon driver. Namely, we'd like to include >>>> counters for bufferes and caches of Linux kernel. The patch itself is >>>> pretty trivial -- no problem there. But before we do that I'd like to >>>> get some input from the QEMU community. >>>> >>>> 1) Is there any reason not to have the stats there? >> Could you please share the usages of reclaimable memory via the stats? > I'll go ahead then and start sending patches. What would be the proper > course of action here? Send patch for the driver first, or send patch > for QEMU first or send both patches right away? If you have both ready, I think it would be fine to send them all. > > >>>> 2) Considering the balloon device is multiplatform (Linux, BSD, >>>> Windows), is there a problem with including buffers/caches? These seem >>>> to be specific to the Linux virtual memory subsystem. Of course, other >>>> OSes could just report zeros. Are there some internal stats on those >>>> OSes that could be filled in? I don't now if such or similar statistic >>>> are available on BSD. On Windows only SystemCache stat looks like >>>> something relevant. Anyone familiar with those OSes has any suggestions? >>>> >>>> >> One of the solutions that I'm thinking about is to make virtio >> platform-ware. > This is not necessary. IIUC the driver does not need to send all the > stats. We can simply treat those stats as specific to Linux driver and > other drivers will not send them. Then QEMU will treat them as if zero > was reported. Just had a quick check, I think that should function well too. QEMU will report -1 for the stats. Best, Wei