From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id 6D7F06B06A5 for ; Thu, 3 Aug 2017 08:24:06 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id p135so5668233qke.0 for ; Thu, 03 Aug 2017 05:24:06 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id o32si19248262qtb.269.2017.08.03.05.24.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 03 Aug 2017 05:24:05 -0700 (PDT) Date: Thu, 3 Aug 2017 15:24:01 +0300 From: "Michael S. Tsirkin" 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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 -- 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