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=-6.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 25B8EC4338F for ; Tue, 17 Aug 2021 14:57:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0047160FA0 for ; Tue, 17 Aug 2021 14:57:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237052AbhHQO6Z (ORCPT ); Tue, 17 Aug 2021 10:58:25 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:43490 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232705AbhHQO6Y (ORCPT ); Tue, 17 Aug 2021 10:58:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629212271; 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=Hk86/KYj3ZK8RgsgOcBS3p9RbAsZ92PjYs1lZc6coX8=; b=anuMZLddL6CqepgZBgq9uqiruYAMtroj+jzqU5ui+XuZZ21+qrNISVfAee0CDmrhlVK2Jc 6zzOFTn5YMmwzoqrv9xgs+ks5UJ2hLuvSXZOg1XucFVEJ0BO/Xu0cze2UJisKtlGlGEjI9 l7o33p7EBvBObuBYVKQXq6DR8mJsl4U= 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-300-yLla6GVTPeifjsf4fyH-kg-1; Tue, 17 Aug 2021 10:57:49 -0400 X-MC-Unique: yLla6GVTPeifjsf4fyH-kg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 83F00EC1A1; Tue, 17 Aug 2021 14:57:48 +0000 (UTC) Received: from horse.redhat.com (unknown [10.22.10.24]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5949B5D6AB; Tue, 17 Aug 2021 14:57:41 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id D5A5A220637; Tue, 17 Aug 2021 10:57:40 -0400 (EDT) Date: Tue, 17 Aug 2021 10:57:40 -0400 From: Vivek Goyal To: JeffleXu Cc: Miklos Szeredi , Stefan Hajnoczi , linux-fsdevel@vger.kernel.org, virtualization@lists.linux-foundation.org, virtio-fs-list , Joseph Qi , Liu Bo Subject: Re: [PATCH v4 0/8] fuse,virtiofs: support per-file DAX Message-ID: References: <20210817022220.17574-1-jefflexu@linux.alibaba.com> <6043c0b8-0ff1-2e11-0dd0-e23f9ff6b952@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6043c0b8-0ff1-2e11-0dd0-e23f9ff6b952@linux.alibaba.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Aug 17, 2021 at 09:22:53PM +0800, JeffleXu wrote: > > > On 8/17/21 8:39 PM, Vivek Goyal wrote: > > On Tue, Aug 17, 2021 at 10:06:53AM +0200, Miklos Szeredi wrote: > >> On Tue, 17 Aug 2021 at 04:22, Jeffle Xu wrote: > >>> > >>> This patchset adds support of per-file DAX for virtiofs, which is > >>> inspired by Ira Weiny's work on ext4[1] and xfs[2]. > >> > >> Can you please explain the background of this change in detail? > >> > >> Why would an admin want to enable DAX for a particular virtiofs file > >> and not for others? > > > > Initially I thought that they needed it because they are downloading > > files on the fly from server. So they don't want to enable dax on the file > > till file is completely downloaded. > > Right, it's our initial requirement. > > > > But later I realized that they should > > be able to block in FUSE_SETUPMAPPING call and make sure associated > > file section has been downloaded before returning and solve the problem. > > So that can't be the primary reason. > > Saying we want to access 4KB of one file inside guest, if it goes > through FUSE request routine, then the fuse daemon only need to download > this 4KB from remote server. But if it goes through DAX, then the fuse > daemon need to download the whole DAX window (e.g., 2MB) from remote > server, so called amplification. Maybe we could decrease the DAX window > size, but it's a trade off. Downloading 2MB chunk should not be a big issue (IMHO). And if this turns out to be real concern, we could experiment with a smaller mapping granularity. > > > > > Other reason mentioned I think was that only certain files benefit > > from DAX. But not much details are there after that. It will be nice > > to hear a more concrete use case and more details about this usage. > > > > Apart from our internal requirement, more fine grained control for DAX > shall be general and more flexible. Glad to hear more discussion from > community. Sure it will be more general and flexible. But there needs to be 1-2 good concrete use cases to justify additional complexity. And I don't think that so far a good use case has come forward. Thanks Vivek 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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 3F3CDC4338F for ; Tue, 17 Aug 2021 14:58:00 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (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 D3E0E60FA0 for ; Tue, 17 Aug 2021 14:57:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org D3E0E60FA0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; 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Tue, 17 Aug 2021 10:57:49 -0400 X-MC-Unique: yLla6GVTPeifjsf4fyH-kg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 83F00EC1A1; Tue, 17 Aug 2021 14:57:48 +0000 (UTC) Received: from horse.redhat.com (unknown [10.22.10.24]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5949B5D6AB; Tue, 17 Aug 2021 14:57:41 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id D5A5A220637; Tue, 17 Aug 2021 10:57:40 -0400 (EDT) Date: Tue, 17 Aug 2021 10:57:40 -0400 From: Vivek Goyal To: JeffleXu Subject: Re: [PATCH v4 0/8] fuse,virtiofs: support per-file DAX Message-ID: References: <20210817022220.17574-1-jefflexu@linux.alibaba.com> <6043c0b8-0ff1-2e11-0dd0-e23f9ff6b952@linux.alibaba.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <6043c0b8-0ff1-2e11-0dd0-e23f9ff6b952@linux.alibaba.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Cc: Miklos Szeredi , virtualization@lists.linux-foundation.org, virtio-fs-list , Joseph Qi , Liu Bo , Stefan Hajnoczi , linux-fsdevel@vger.kernel.org X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Tue, Aug 17, 2021 at 09:22:53PM +0800, JeffleXu wrote: > > > On 8/17/21 8:39 PM, Vivek Goyal wrote: > > On Tue, Aug 17, 2021 at 10:06:53AM +0200, Miklos Szeredi wrote: > >> On Tue, 17 Aug 2021 at 04:22, Jeffle Xu wrote: > >>> > >>> This patchset adds support of per-file DAX for virtiofs, which is > >>> inspired by Ira Weiny's work on ext4[1] and xfs[2]. > >> > >> Can you please explain the background of this change in detail? > >> > >> Why would an admin want to enable DAX for a particular virtiofs file > >> and not for others? > > > > Initially I thought that they needed it because they are downloading > > files on the fly from server. So they don't want to enable dax on the file > > till file is completely downloaded. > > Right, it's our initial requirement. > > > > But later I realized that they should > > be able to block in FUSE_SETUPMAPPING call and make sure associated > > file section has been downloaded before returning and solve the problem. > > So that can't be the primary reason. > > Saying we want to access 4KB of one file inside guest, if it goes > through FUSE request routine, then the fuse daemon only need to download > this 4KB from remote server. But if it goes through DAX, then the fuse > daemon need to download the whole DAX window (e.g., 2MB) from remote > server, so called amplification. Maybe we could decrease the DAX window > size, but it's a trade off. Downloading 2MB chunk should not be a big issue (IMHO). And if this turns out to be real concern, we could experiment with a smaller mapping granularity. > > > > > Other reason mentioned I think was that only certain files benefit > > from DAX. But not much details are there after that. It will be nice > > to hear a more concrete use case and more details about this usage. > > > > Apart from our internal requirement, more fine grained control for DAX > shall be general and more flexible. Glad to hear more discussion from > community. Sure it will be more general and flexible. But there needs to be 1-2 good concrete use cases to justify additional complexity. And I don't think that so far a good use case has come forward. Thanks Vivek _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 17 Aug 2021 10:57:40 -0400 From: Vivek Goyal Message-ID: References: <20210817022220.17574-1-jefflexu@linux.alibaba.com> <6043c0b8-0ff1-2e11-0dd0-e23f9ff6b952@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6043c0b8-0ff1-2e11-0dd0-e23f9ff6b952@linux.alibaba.com> Subject: Re: [Virtio-fs] [PATCH v4 0/8] fuse,virtiofs: support per-file DAX List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: JeffleXu Cc: Miklos Szeredi , virtualization@lists.linux-foundation.org, virtio-fs-list , Joseph Qi , linux-fsdevel@vger.kernel.org On Tue, Aug 17, 2021 at 09:22:53PM +0800, JeffleXu wrote: > > > On 8/17/21 8:39 PM, Vivek Goyal wrote: > > On Tue, Aug 17, 2021 at 10:06:53AM +0200, Miklos Szeredi wrote: > >> On Tue, 17 Aug 2021 at 04:22, Jeffle Xu wrote: > >>> > >>> This patchset adds support of per-file DAX for virtiofs, which is > >>> inspired by Ira Weiny's work on ext4[1] and xfs[2]. > >> > >> Can you please explain the background of this change in detail? > >> > >> Why would an admin want to enable DAX for a particular virtiofs file > >> and not for others? > > > > Initially I thought that they needed it because they are downloading > > files on the fly from server. So they don't want to enable dax on the file > > till file is completely downloaded. > > Right, it's our initial requirement. > > > > But later I realized that they should > > be able to block in FUSE_SETUPMAPPING call and make sure associated > > file section has been downloaded before returning and solve the problem. > > So that can't be the primary reason. > > Saying we want to access 4KB of one file inside guest, if it goes > through FUSE request routine, then the fuse daemon only need to download > this 4KB from remote server. But if it goes through DAX, then the fuse > daemon need to download the whole DAX window (e.g., 2MB) from remote > server, so called amplification. Maybe we could decrease the DAX window > size, but it's a trade off. Downloading 2MB chunk should not be a big issue (IMHO). And if this turns out to be real concern, we could experiment with a smaller mapping granularity. > > > > > Other reason mentioned I think was that only certain files benefit > > from DAX. But not much details are there after that. It will be nice > > to hear a more concrete use case and more details about this usage. > > > > Apart from our internal requirement, more fine grained control for DAX > shall be general and more flexible. Glad to hear more discussion from > community. Sure it will be more general and flexible. But there needs to be 1-2 good concrete use cases to justify additional complexity. And I don't think that so far a good use case has come forward. Thanks Vivek