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Fri, 29 Nov 2019 09:27:27 +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 4FAF35D9C5; Fri, 29 Nov 2019 09:27:16 +0000 (UTC) Date: Fri, 29 Nov 2019 09:27:13 +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: <20191129092713.GA2260471@redhat.com> References: <20191128141518.628245-1-marcandre.lureau@redhat.com> <20191129070253.5hwksjrapomk434x@sirius.home.kraxel.org> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: -xiIzvHSNIKlWgdjl2ABcw-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: 207.211.31.81 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 11:30:51AM +0400, Marc-Andr=C3=A9 Lureau wrote: > Hi >=20 > On Fri, Nov 29, 2019 at 11:03 AM Gerd Hoffmann wrote: > > > > On Thu, Nov 28, 2019 at 06:15:16PM +0400, Marc-Andr=C3=A9 Lureau wrote: > > > 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 setups, > > > that will make the -mem-path or anonymouse memory shareable. > > > > Is it an option to just use memfd by default (if available)? >=20 > 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 no 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. 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= :|