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[82.29.237.198]) by smtp.gmail.com with ESMTPSA id p14sm2022341wro.3.2021.08.17.03.37.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Aug 2021 03:37:22 -0700 (PDT) Date: Tue, 17 Aug 2021 11:37:20 +0100 From: "Dr. David Alan Gilbert" To: Miklos Szeredi Cc: Jeffle Xu , virtualization@lists.linux-foundation.org, virtio-fs-list , Joseph Qi , linux-fsdevel@vger.kernel.org, Vivek Goyal Subject: Re: [Virtio-fs] [PATCH v4 0/8] fuse,virtiofs: support per-file DAX Message-ID: References: <20210817022220.17574-1-jefflexu@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.0.7 (2021-05-04) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org * Miklos Szeredi (miklos@szeredi.hu) wrote: > On Tue, 17 Aug 2021 at 11:32, Dr. David Alan Gilbert > wrote: > > > > * Miklos Szeredi (miklos@szeredi.hu) 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? > > > > Where we're contending on virtiofs dax cache size it makes a lot of > > sense; it's quite expensive for us to map something into the cache > > (especially if we push something else out), so selectively DAXing files > > that are expected to be hot could help reduce cache churn. > > If this is a performance issue, it should be fixed in a way that > doesn't require hand tuning like you suggest, I think. I'd agree that would be nice; however: a) It looks like other filesystems already gave something admin selectable b) Trying to write clever heuristics is only going to work in some cases; being able to say 'DAX this directory' might work better in practice. > I'm not sure what the ext4/xfs case for per-file DAX is. Maybe that > can help understand the virtiofs case as well. Yep, I don't understand the case with real nvdimm hardware. Dave > Thanks, > Miklos > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK 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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 0BFACC4338F for ; Tue, 17 Aug 2021 10:37:37 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (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 A597D604AC for ; Tue, 17 Aug 2021 10:37:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A597D604AC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 714ED40368; Tue, 17 Aug 2021 10:37:36 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id iw87te75cgv2; Tue, 17 Aug 2021 10:37:32 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp2.osuosl.org (Postfix) with ESMTPS id 0F351401CE; Tue, 17 Aug 2021 10:37:31 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id B0AC5C001A; Tue, 17 Aug 2021 10:37:31 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id A193FC000E for ; Tue, 17 Aug 2021 10:37:30 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 7D505401CE for ; Tue, 17 Aug 2021 10:37:30 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ytSNuOf-K6ps for ; Tue, 17 Aug 2021 10:37:29 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by smtp2.osuosl.org (Postfix) with ESMTPS id 89D12400E9 for ; Tue, 17 Aug 2021 10:37:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629196648; 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=ylAqgdbrJZr9xkOSrjkKyy1IPEuT4QXdJGcAzYJ78VY=; b=igsu1UmpNTW0nrWwKeO/271xyHuhOOwFRNAdZpecIHCkb5LiaDUKEGeTGwray4y9VInJHy bn8cnPVw3qdM3SwYb3u0PL3+8gVoY/xHoOTocPPu6rJQUtx6BCIDidPIhHWabYW8tQ/RX8 1EqTUaW4p7d0GN+UdPtIvcrbn5Guw3k= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-338-cSS4PGC6OyWRsNenUV9ZLw-1; Tue, 17 Aug 2021 06:37:25 -0400 X-MC-Unique: cSS4PGC6OyWRsNenUV9ZLw-1 Received: by mail-wm1-f69.google.com with SMTP id z15-20020a7bc7cf0000b02902e6a68ffd3cso694996wmk.2 for ; Tue, 17 Aug 2021 03:37:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=ylAqgdbrJZr9xkOSrjkKyy1IPEuT4QXdJGcAzYJ78VY=; b=PibvNsemo1QUGO64YxMxWFzsHUo20KZPkL1CSrr0fFXBYebDJ0pd8v9QH3pill7xCa iALGZyhMeqZP27d0KW19sjpSi2zoFjvgOJJSOcTqxfAq6orCvt+JgW6Lzji+u7TeVVbe FsWSvBns0TRhJ3UR6XbdAHjg/OwmL4bhoW0we1Z5agm0kdu805hMo7m6mBZiNRdpD4CL HTWDpmHuHM+eIrKK9+t3WqsL5c5bSbZvRw6UXVPszyX/y0sktM4q0AEZNLIRSjG59bLq d9K75E6S96jnBJhcv2G2DPYEJvx1pgJUXantHaPz4O6sqPx5Ob0VcKdi9eRKE1R40lD9 salw== X-Gm-Message-State: AOAM532Gh5Kzw86A6j8zVSkw+JP24ieCTLOcMMLttSnB3Lz3aWPgFBoC tXuAQ2SNSk6aUO+kKT0CgJ1879FUMLrEjQZDJqC7klu9FZnMcGWH79/82VvXw+t6QV+EwavuD5u uK7EWFYyJAOw/h+NpGFjN2GrPvW/FtwfsKEATV6FF/w== X-Received: by 2002:a5d:4808:: with SMTP id l8mr3194592wrq.349.1629196643850; Tue, 17 Aug 2021 03:37:23 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwIw4MIhbeuweeJtzdTPOXRFRTTdHSmvBxHZb0P4/fi6Kf+/mQJrX0KPtKDSsy4idKQTTiLcg== X-Received: by 2002:a5d:4808:: with SMTP id l8mr3194578wrq.349.1629196643725; Tue, 17 Aug 2021 03:37:23 -0700 (PDT) Received: from work-vm (cpc109021-salf6-2-0-cust453.10-2.cable.virginm.net. [82.29.237.198]) by smtp.gmail.com with ESMTPSA id p14sm2022341wro.3.2021.08.17.03.37.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Aug 2021 03:37:22 -0700 (PDT) Date: Tue, 17 Aug 2021 11:37:20 +0100 From: "Dr. David Alan Gilbert" To: Miklos Szeredi Subject: Re: [Virtio-fs] [PATCH v4 0/8] fuse,virtiofs: support per-file DAX Message-ID: References: <20210817022220.17574-1-jefflexu@linux.alibaba.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.0.7 (2021-05-04) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Joseph Qi , virtualization@lists.linux-foundation.org, virtio-fs-list , linux-fsdevel@vger.kernel.org, Vivek Goyal 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" * Miklos Szeredi (miklos@szeredi.hu) wrote: > On Tue, 17 Aug 2021 at 11:32, Dr. David Alan Gilbert > wrote: > > > > * Miklos Szeredi (miklos@szeredi.hu) 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? > > > > Where we're contending on virtiofs dax cache size it makes a lot of > > sense; it's quite expensive for us to map something into the cache > > (especially if we push something else out), so selectively DAXing files > > that are expected to be hot could help reduce cache churn. > > If this is a performance issue, it should be fixed in a way that > doesn't require hand tuning like you suggest, I think. I'd agree that would be nice; however: a) It looks like other filesystems already gave something admin selectable b) Trying to write clever heuristics is only going to work in some cases; being able to say 'DAX this directory' might work better in practice. > I'm not sure what the ext4/xfs case for per-file DAX is. Maybe that > can help understand the virtiofs case as well. Yep, I don't understand the case with real nvdimm hardware. Dave > Thanks, > Miklos > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK _______________________________________________ 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 11:37:20 +0100 From: "Dr. David Alan Gilbert" Message-ID: References: <20210817022220.17574-1-jefflexu@linux.alibaba.com> MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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: Miklos Szeredi Cc: Joseph Qi , virtualization@lists.linux-foundation.org, virtio-fs-list , linux-fsdevel@vger.kernel.org, Jeffle Xu , Vivek Goyal * Miklos Szeredi (miklos@szeredi.hu) wrote: > On Tue, 17 Aug 2021 at 11:32, Dr. David Alan Gilbert > wrote: > > > > * Miklos Szeredi (miklos@szeredi.hu) 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? > > > > Where we're contending on virtiofs dax cache size it makes a lot of > > sense; it's quite expensive for us to map something into the cache > > (especially if we push something else out), so selectively DAXing files > > that are expected to be hot could help reduce cache churn. > > If this is a performance issue, it should be fixed in a way that > doesn't require hand tuning like you suggest, I think. I'd agree that would be nice; however: a) It looks like other filesystems already gave something admin selectable b) Trying to write clever heuristics is only going to work in some cases; being able to say 'DAX this directory' might work better in practice. > I'm not sure what the ext4/xfs case for per-file DAX is. Maybe that > can help understand the virtiofs case as well. Yep, I don't understand the case with real nvdimm hardware. Dave > Thanks, > Miklos > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK