From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 6AEDE6B05C7 for ; Mon, 31 Jul 2017 03:39:09 -0400 (EDT) Received: by mail-pg0-f70.google.com with SMTP id y129so276029268pgy.1 for ; Mon, 31 Jul 2017 00:39:09 -0700 (PDT) Received: from mga04.intel.com (mga04.intel.com. [192.55.52.120]) by mx.google.com with ESMTPS id y94si8101625plh.881.2017.07.31.00.39.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 31 Jul 2017 00:39:08 -0700 (PDT) Message-ID: <597EDF3D.8020101@intel.com> Date: Mon, 31 Jul 2017 15:41:49 +0800 From: Wei Wang MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org