From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D781C67839 for ; Thu, 13 Dec 2018 21:58:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD64C20870 for ; Thu, 13 Dec 2018 21:58:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CD64C20870 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728128AbeLMV6J (ORCPT ); Thu, 13 Dec 2018 16:58:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35080 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbeLMV6H (ORCPT ); Thu, 13 Dec 2018 16:58:07 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 12464307EAA1; Thu, 13 Dec 2018 21:58:07 +0000 (UTC) Received: from redhat.com (ovpn-121-220.rdu2.redhat.com [10.10.121.220]) by smtp.corp.redhat.com (Postfix) with SMTP id AB99761B77; Thu, 13 Dec 2018 21:58:05 +0000 (UTC) Date: Thu, 13 Dec 2018 16:58:04 -0500 From: "Michael S. Tsirkin" To: Konrad Rzeszutek Wilk Cc: Jason Wang , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 3/3] vhost: access vq metadata through kernel virtual address Message-ID: <20181213165731-mutt-send-email-mst@kernel.org> References: <20181213101022.12475-1-jasowang@redhat.com> <20181213101022.12475-4-jasowang@redhat.com> <20181213102713-mutt-send-email-mst@kernel.org> <20181213211840.GC18692@char.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181213211840.GC18692@char.us.oracle.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Thu, 13 Dec 2018 21:58:07 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 13, 2018 at 04:18:40PM -0500, Konrad Rzeszutek Wilk wrote: > .giant snip.. > > > + npinned = get_user_pages_fast(uaddr, npages, write, pages); > > > + if (npinned != npages) > > > + goto err; > > > + > > > > As I said I have doubts about the whole approach, but this > > implementation in particular isn't a good idea > > as it keeps the page around forever. > > So no THP, no NUMA rebalancing, userspace-controlled > > amount of memory locked up and not accounted for. > > > > Don't get me wrong it's a great patch in an ideal world. > > But then in an ideal world no barriers smap etc are necessary at all. > > So .. suggestions on how this could be accepted? As in other ways > where we still get vmap and the issues you mentioned are not troubling you? > > Thanks! I'd suggest leave vmap alone and find ways to speed up accesses that can fault. -- MST