From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752110AbdGaHjJ (ORCPT ); Mon, 31 Jul 2017 03:39:09 -0400 Received: from mga09.intel.com ([134.134.136.24]:26436 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751956AbdGaHjI (ORCPT ); Mon, 31 Jul 2017 03:39:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.40,441,1496127600"; d="scan'208";a="1157208491" Message-ID: <597EDF3D.8020101@intel.com> Date: Mon, 31 Jul 2017 15:41:49 +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: linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtualization@lists.linux-foundation.org, mst@redhat.com, mawilcox@microsoft.com, dave.hansen@intel.com, akpm@linux-foundation.org, zhenwei.pi@youruncloud.com Subject: Re: [PATCH] mm: don't zero ballooned pages References: <1501474413-21580-1-git-send-email-wei.w.wang@intel.com> <20170731065508.GE13036@dhcp22.suse.cz> In-Reply-To: <20170731065508.GE13036@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 On 07/31/2017 02:55 PM, Michal Hocko wrote: > On Mon 31-07-17 12:13:33, Wei Wang wrote: >> Ballooned pages will be marked as MADV_DONTNEED by the hypervisor and >> shouldn't be given to the host ksmd to scan. > Could you point me where this MADV_DONTNEED is done, please? Sure. It's done in the hypervisor when the balloon pages are received. Please see line 40 at https://github.com/qemu/qemu/blob/master/hw/virtio/virtio-balloon.c > >> Therefore, it is not >> necessary to zero ballooned pages, which is very time consuming when >> the page amount is large. The ongoing fast balloon tests show that the >> time to balloon 7G pages is increased from ~491ms to 2.8 seconds with >> __GFP_ZERO added. So, this patch removes the flag. > Please make it obvious that this is a revert of bb01b64cfab7 > ("mm/balloon_compaction.c: enqueue zero page to balloon device"). > > Ok, will do. Best, Wei