From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751739AbdHCMYG (ORCPT ); Thu, 3 Aug 2017 08:24:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39482 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751184AbdHCMYE (ORCPT ); Thu, 3 Aug 2017 08:24:04 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 443D54ACC7 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=mst@redhat.com Date: Thu, 3 Aug 2017 15:24:01 +0300 From: "Michael S. Tsirkin" To: Wei Wang Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtualization@lists.linux-foundation.org, mhocko@kernel.org, zhenwei.pi@youruncloud.com, akpm@linux-foundation.org, dave.hansen@intel.com, mawilcox@microsoft.com Subject: Re: [PATCH RESEND] mm: don't zero ballooned pages Message-ID: <20170803151844-mutt-send-email-mst@kernel.org> References: <1501761557-9758-1-git-send-email-wei.w.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1501761557-9758-1-git-send-email-wei.w.wang@intel.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 03 Aug 2017 12:24:04 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 03, 2017 at 07:59:17PM +0800, Wei Wang wrote: > This patch is a revert of 'commit bb01b64cfab7 ("mm/balloon_compaction.c: > enqueue zero page to balloon device")' > > Ballooned pages will be marked as MADV_DONTNEED by the hypervisor and > shouldn't be given to the host ksmd to scan. 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. > > Signed-off-by: Wei Wang > Cc: Michal Hocko > Cc: Michael S. Tsirkin Fixes: bb01b64cfab7 ("mm/balloon_compaction.c: enqueue zero page to balloon device") Looks like hypervisor is better placed to zero these if it wants to. If it can't for some reason, this change would need a feature bit to avoid adding extra work for all guests. Acked-by: Michael S. Tsirkin > --- > mm/balloon_compaction.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c > index 9075aa5..b06d9fe 100644 > --- a/mm/balloon_compaction.c > +++ b/mm/balloon_compaction.c > @@ -24,7 +24,7 @@ struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info) > { > unsigned long flags; > struct page *page = alloc_page(balloon_mapping_gfp_mask() | > - __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_ZERO); > + __GFP_NOMEMALLOC | __GFP_NORETRY); > if (!page) > return NULL; > > -- > 2.7.4