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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 21825C4338F for ; Tue, 17 Aug 2021 10:09:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 02FED60F41 for ; Tue, 17 Aug 2021 10:09:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236297AbhHQKKZ (ORCPT ); Tue, 17 Aug 2021 06:10:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53146 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236472AbhHQKKY (ORCPT ); Tue, 17 Aug 2021 06:10:24 -0400 Received: from mail-vk1-xa30.google.com (mail-vk1-xa30.google.com [IPv6:2607:f8b0:4864:20::a30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4BA6C0613CF for ; Tue, 17 Aug 2021 03:09:51 -0700 (PDT) Received: by mail-vk1-xa30.google.com with SMTP id j196so3306373vkj.2 for ; Tue, 17 Aug 2021 03:09:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=L5HiMY324/mbIiHBmv8ouk9uhF1dk69cnwR9QB4zoKM=; b=KpRR7+8nUUVsoxbdOgYQucb4dRqGY/Ztix1ugMqRzceQBu4muJt6dC7z66GwPBj84e V3Am9kEWnBv01osYvcdUtdn2dTZ36LI/wWYbIjsYs7ZuZcoNzyGaIN6chtnCdAjldYFY wINqi1LA8R72QTsmD5zTtwaSWYMXBjNt8IDBM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=L5HiMY324/mbIiHBmv8ouk9uhF1dk69cnwR9QB4zoKM=; b=cSjzmReVOQCLFfI6I+0Azg5JcE5ob69tNBX+Vg4/dfiWnD/UUxbu3+0zwpYzwfebc4 PLA+nomTeNo6GX7snASMmLrWHfod6vIGkV6j+cRyR7xV0b0G1kAfrKJgxtWMwPNAgHk8 JzAIqfhhen2KXbf19NVmF5BoZ+IvR3G6fDt0qCxHDeIYVZvRy7r6TBAEKD0WkxwfpLs4 sGfSy3ykwp86DScM+laWGWHXKBst5yKbyg6/A0BWBRkbKG/TVn/Yl8N7W5IAUP/HwgiC j9ePmivGYJ7E5o6uRRfFesVkIKLn7pzWb/AFoi8WWm3LbwS4h1QfdtMLBCUaQIluIdE5 ZdLQ== X-Gm-Message-State: AOAM5321bo0A8zlT1ddPHblCC7z5SnDnyGZ/vwCOXuEsEuhC6jMgg/RC 8V16prtBTSxI2mJWxSgm00lEHHrfXrFbedM5+1kX5Q== X-Google-Smtp-Source: ABdhPJx8pk1uqplN3trcA8W23P3kKfETTVV14540Sqzr1MmA7GLiXmHKTRoBH4e7h1pdUu4Y+EYLENTS3MQcKJKUrR4= X-Received: by 2002:a1f:d442:: with SMTP id l63mr1936973vkg.3.1629194990938; Tue, 17 Aug 2021 03:09:50 -0700 (PDT) MIME-Version: 1.0 References: <20210817022220.17574-1-jefflexu@linux.alibaba.com> In-Reply-To: From: Miklos Szeredi Date: Tue, 17 Aug 2021 12:09:40 +0200 Message-ID: Subject: Re: [Virtio-fs] [PATCH v4 0/8] fuse,virtiofs: support per-file DAX To: "Dr. David Alan Gilbert" Cc: Jeffle Xu , virtualization@lists.linux-foundation.org, virtio-fs-list , Joseph Qi , linux-fsdevel@vger.kernel.org, Vivek Goyal Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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'm not sure what the ext4/xfs case for per-file DAX is. Maybe that can help understand the virtiofs case as well. Thanks, Miklos From mboxrd@z Thu Jan 1 00:00:00 1970 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=L5HiMY324/mbIiHBmv8ouk9uhF1dk69cnwR9QB4zoKM=; b=KpRR7+8nUUVsoxbdOgYQucb4dRqGY/Ztix1ugMqRzceQBu4muJt6dC7z66GwPBj84e V3Am9kEWnBv01osYvcdUtdn2dTZ36LI/wWYbIjsYs7ZuZcoNzyGaIN6chtnCdAjldYFY wINqi1LA8R72QTsmD5zTtwaSWYMXBjNt8IDBM= MIME-Version: 1.0 References: <20210817022220.17574-1-jefflexu@linux.alibaba.com> In-Reply-To: From: Miklos Szeredi Date: Tue, 17 Aug 2021 12:09:40 +0200 Message-ID: Content-Type: text/plain; charset="UTF-8" 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: "Dr. David Alan Gilbert" Cc: Joseph Qi , virtualization@lists.linux-foundation.org, virtio-fs-list , linux-fsdevel@vger.kernel.org, Jeffle Xu , Vivek Goyal 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'm not sure what the ext4/xfs case for per-file DAX is. Maybe that can help understand the virtiofs case as well. Thanks, Miklos