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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,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 7E231C433B4 for ; Thu, 6 May 2021 15:46:20 +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 E5894610A7 for ; Thu, 6 May 2021 15:46:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E5894610A7 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]:53986 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1legCf-0002qx-PB for qemu-devel@archiver.kernel.org; Thu, 06 May 2021 11:46:18 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48188) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1leg4g-00067p-4t for qemu-devel@nongnu.org; Thu, 06 May 2021 11:38:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:48962) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1leg4X-0008Ka-BK for qemu-devel@nongnu.org; Thu, 06 May 2021 11:38:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620315472; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vuITwmuYXnyYs9RWJOpC5nRmFEr6HVUlITG5r7+4z2c=; b=Pak8yAEVx1RREu44zPkenAIj5Z2HlgxaIbqv3R5ob4GQspnWvYQBXBh5dRWgvn0yGNl+Bz R6DD7hyX/3nNFX6SMK27mCHbbniBJv56sMfh+ygqfJaa000Rdm+ts2WOZ99YusaScmgIYg avRFrgJTqAZYhXwJ0J+O0DdkhzVjN8g= 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-412-oDU_M98XMa654shsfMxbpQ-1; Thu, 06 May 2021 11:37:49 -0400 X-MC-Unique: oDU_M98XMa654shsfMxbpQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EB8DD6D26B; Thu, 6 May 2021 15:37:48 +0000 (UTC) Received: from localhost (ovpn-115-109.ams2.redhat.com [10.36.115.109]) by smtp.corp.redhat.com (Postfix) with ESMTP id F3FF160C25; Thu, 6 May 2021 15:37:44 +0000 (UTC) Date: Thu, 6 May 2021 16:37:43 +0100 From: Stefan Hajnoczi To: "Dr. David Alan Gilbert (git)" Subject: Re: [PATCH v3 00/26] virtiofs dax patches Message-ID: References: <20210428110100.27757-1-dgilbert@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210428110100.27757-1-dgilbert@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="lqhZRkdxYdMqldv1" Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.69, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: , Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org, vgoyal@redhat.com, groug@kaod.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --lqhZRkdxYdMqldv1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 28, 2021 at 12:00:34PM +0100, Dr. David Alan Gilbert (git) wrot= e: > From: "Dr. David Alan Gilbert" >=20 > This series adds support for acceleration of virtiofs via DAX > mapping, using features added in the 5.11 Linux kernel. >=20 > DAX originally existed in the kernel for mapping real storage > devices directly into memory, so that reads/writes turn into > reads/writes directly mapped into the storage device. >=20 > virtiofs's DAX support is similar; a PCI BAR is exposed on the > virtiofs device corresponding to a DAX 'cache' of a user defined size. > The guest daemon then requests files to be mapped into that cache; > when that happens the virtiofsd sends filedescriptors and commands back > to the QEMU that mmap's those files directly into the memory slot > exposed to kvm. The guest can then directly read/write to the files > exposed by virtiofs by reading/writing into the BAR. >=20 > A typical invocation would be: > -device vhost-user-fs-pci,queue-size=3D1024,chardev=3Dchar0,tag=3Dmy= fs,cache-size=3D4G >=20 > and then the guest must mount with -o dax >=20 > Note that the cache doesn't really take VM up on the host, because > everything placed there is just an mmap of a file, so you can afford > to use quite a large cache size. >=20 > Unlike a real DAX device, the cache is a finite size that's > potentially smaller than the underlying filesystem (especially when > mapping granuality is taken into account). Mapping, unmapping and > remapping must take place to juggle files into the cache if it's too > small. Some workloads benefit more than others. >=20 > Gotchas: > a) If something else on the host truncates an mmap'd file, > kvm gets rather upset; for this reason it's advised that DAX is > currently only suitable for use on non-shared filesystems. >=20 > (This series, with a couple of other patches, is at: > https://gitlab.com/virtio-fs/qemu/-/tree/dgilbert-dax-2021-04-28 ) Overall this looks close but I don't think the FSETID support should be added to QEMU. Please see my comment on the final patch. Stefan --lqhZRkdxYdMqldv1 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmCUDUcACgkQnKSrs4Gr c8j9jwf+JxfBvM1p05OJ2XVmZKvl3iREksfk277QH1LHCLzurox+5YovRH9TAQ+F ZJNQH23RrTYnJIGX2bxU5eG+xeOVY3LCn42gGg/uQPGTiqdK+fGm6CNwAHKGAogE 42pBqdOO9xxDCQxf3XbH1Uf5RHgGpj/M7kN9pnvna47WuKvTZypORRNCqYQyg0PA Tzkrs636SFu6bpj0Sp+EWOBv3a94eEnFsHMmYqjxkkeprppK6V7oQ7eYRlXhpqJx RvTQpfUCKtqmZGYNIxpxUqj6fZ0docDCxERkAEC0CJ9zcZsy2/FFvlDQA3x22Kby 6yiwtkPhSlXkKgq30szKNZjrJBx8KQ== =aKdo -----END PGP SIGNATURE----- --lqhZRkdxYdMqldv1-- From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 6 May 2021 16:37:43 +0100 From: Stefan Hajnoczi Message-ID: References: <20210428110100.27757-1-dgilbert@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="lqhZRkdxYdMqldv1" Content-Disposition: inline In-Reply-To: <20210428110100.27757-1-dgilbert@redhat.com> Subject: Re: [Virtio-fs] [PATCH v3 00/26] virtiofs dax patches List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org, vgoyal@redhat.com --lqhZRkdxYdMqldv1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 28, 2021 at 12:00:34PM +0100, Dr. David Alan Gilbert (git) wrot= e: > From: "Dr. David Alan Gilbert" >=20 > This series adds support for acceleration of virtiofs via DAX > mapping, using features added in the 5.11 Linux kernel. >=20 > DAX originally existed in the kernel for mapping real storage > devices directly into memory, so that reads/writes turn into > reads/writes directly mapped into the storage device. >=20 > virtiofs's DAX support is similar; a PCI BAR is exposed on the > virtiofs device corresponding to a DAX 'cache' of a user defined size. > The guest daemon then requests files to be mapped into that cache; > when that happens the virtiofsd sends filedescriptors and commands back > to the QEMU that mmap's those files directly into the memory slot > exposed to kvm. The guest can then directly read/write to the files > exposed by virtiofs by reading/writing into the BAR. >=20 > A typical invocation would be: > -device vhost-user-fs-pci,queue-size=3D1024,chardev=3Dchar0,tag=3Dmy= fs,cache-size=3D4G >=20 > and then the guest must mount with -o dax >=20 > Note that the cache doesn't really take VM up on the host, because > everything placed there is just an mmap of a file, so you can afford > to use quite a large cache size. >=20 > Unlike a real DAX device, the cache is a finite size that's > potentially smaller than the underlying filesystem (especially when > mapping granuality is taken into account). Mapping, unmapping and > remapping must take place to juggle files into the cache if it's too > small. Some workloads benefit more than others. >=20 > Gotchas: > a) If something else on the host truncates an mmap'd file, > kvm gets rather upset; for this reason it's advised that DAX is > currently only suitable for use on non-shared filesystems. >=20 > (This series, with a couple of other patches, is at: > https://gitlab.com/virtio-fs/qemu/-/tree/dgilbert-dax-2021-04-28 ) Overall this looks close but I don't think the FSETID support should be added to QEMU. Please see my comment on the final patch. Stefan --lqhZRkdxYdMqldv1 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmCUDUcACgkQnKSrs4Gr c8j9jwf+JxfBvM1p05OJ2XVmZKvl3iREksfk277QH1LHCLzurox+5YovRH9TAQ+F ZJNQH23RrTYnJIGX2bxU5eG+xeOVY3LCn42gGg/uQPGTiqdK+fGm6CNwAHKGAogE 42pBqdOO9xxDCQxf3XbH1Uf5RHgGpj/M7kN9pnvna47WuKvTZypORRNCqYQyg0PA Tzkrs636SFu6bpj0Sp+EWOBv3a94eEnFsHMmYqjxkkeprppK6V7oQ7eYRlXhpqJx RvTQpfUCKtqmZGYNIxpxUqj6fZ0docDCxERkAEC0CJ9zcZsy2/FFvlDQA3x22Kby 6yiwtkPhSlXkKgq30szKNZjrJBx8KQ== =aKdo -----END PGP SIGNATURE----- --lqhZRkdxYdMqldv1--