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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 2E048C432C0 for ; Fri, 29 Nov 2019 10:01:29 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EC9562176D for ; Fri, 29 Nov 2019 10:01:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DeBL4Mmp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC9562176D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:56556 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iad5Z-0001W2-IK for qemu-devel@archiver.kernel.org; Fri, 29 Nov 2019 05:01:25 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:39281) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iacnf-00076l-Ud for qemu-devel@nongnu.org; Fri, 29 Nov 2019 04:42:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iacna-0005em-OK for qemu-devel@nongnu.org; Fri, 29 Nov 2019 04:42:53 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:57061 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iacna-0005cH-E0 for qemu-devel@nongnu.org; Fri, 29 Nov 2019 04:42:50 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575020568; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jYw7kp3QQGa4HNw3G8bjQxnuMXdR/1d5pl6k5N2a6Vs=; b=DeBL4Mmp8OOecgcDrwxgMUyY+TWkkUEmGR2a9GO9lBMEAsd0W4/f/sNIKh4f+Cru6o3Bmx cWFa9KaGvnyOfs3DT4SZftoY7hI1M4CcLLcnmh/RJYSUwza38mkNl8QN3fHzUmmfWnum8v CzPGzDFLGnmHrcVuedBnVEvS1yhzva8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-195-1EejB-OWOX-C-f4OQ3IyUg-1; Fri, 29 Nov 2019 04:42:45 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2FC8C10054E3; Fri, 29 Nov 2019 09:42:44 +0000 (UTC) Received: from redhat.com (ovpn-112-31.ams2.redhat.com [10.36.112.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7F2CE60BE2; Fri, 29 Nov 2019 09:42:33 +0000 (UTC) Date: Fri, 29 Nov 2019 09:42:30 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Subject: Re: [PATCH 0/2] RFC: add -mem-shared option Message-ID: <20191129094230.GE2260471@redhat.com> References: <20191128141518.628245-1-marcandre.lureau@redhat.com> <20191129070253.5hwksjrapomk434x@sirius.home.kraxel.org> <20191129092713.GA2260471@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: 1EejB-OWOX-C-f4OQ3IyUg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Eduardo Habkost , qemu-devel , Gerd Hoffmann , Stefan Hajnoczi , Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Nov 29, 2019 at 01:31:11PM +0400, Marc-Andr=C3=A9 Lureau wrote: > Hi >=20 > On Fri, Nov 29, 2019 at 1:27 PM Daniel P. Berrang=C3=A9 wrote: > > > > On Fri, Nov 29, 2019 at 11:30:51AM +0400, Marc-Andr=C3=A9 Lureau wrote: > > > Hi > > > > > > On Fri, Nov 29, 2019 at 11:03 AM Gerd Hoffmann wr= ote: > > > > > > > > On Thu, Nov 28, 2019 at 06:15:16PM +0400, Marc-Andr=C3=A9 Lureau wr= ote: > > > > > Hi, > > > > > > > > > > Setting up shared memory for vhost-user is a bit complicated from > > > > > command line, as it requires NUMA setup such as: m 4G -object > > > > > memory-backend-file,id=3Dmem,size=3D4G,mem-path=3D/dev/shm,share= =3Don -numa > > > > > node,memdev=3Dmem. > > > > > > > > > > Instead, I suggest to add a -mem-shared option for non-numa setup= s, > > > > > that will make the -mem-path or anonymouse memory shareable. > > > > > > > > Is it an option to just use memfd by default (if available)? > > > > > > Yes, with a fallback path currently using a temporary file under /tmp > > > (we may want to use shm_open() instead, or a different location such > > > as XDG_RUNTIME_DIR? - and use O_TMPFILE) > > > > We can't assume either /tmp or XDG_RUNTIME_DIR is on tmpfs as that is n= o > > where near standard across all OS distros, and even if on tmpfs these > > dirs can be size limited to a significant subset of available RAM. IOW > > we can't safely use them unless explicitly told to. >=20 > Is shm_open() acceptable instead? >=20 > Imho, -mem-shared should do a best effort by default, but can fail. Possibly, but if we're relying on shm_open choosing the path, then its harder for users to know what files to clean up when QEMU crashes or otherwise exits wthout a shm_unlink Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberrange= :| |: https://libvirt.org -o- https://fstop138.berrange.com= :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange= :|