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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 12938C32771 for ; Mon, 6 Jan 2020 07:25:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D887A24650 for ; Mon, 6 Jan 2020 07:25:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="tegvSo1+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726668AbgAFHZW (ORCPT ); Mon, 6 Jan 2020 02:25:22 -0500 Received: from mail-wm1-f45.google.com ([209.85.128.45]:50551 "EHLO mail-wm1-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726488AbgAFHZV (ORCPT ); Mon, 6 Jan 2020 02:25:21 -0500 Received: by mail-wm1-f45.google.com with SMTP id a5so14006990wmb.0 for ; Sun, 05 Jan 2020 23:25:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to:cc; bh=Udr2VC/34D/ej3jNtnHKlwamBndRUt0c7YEySUS9AYk=; b=tegvSo1+pMilhE+TKyGCXpLfcr2ODsbxMl4yqS/RBIwjBmObGk5V7Hyd0urVNdFLnB yQ73s0FwM6SUJrkJlTTktD3/gtYciOXhdbQWvGSAFbHeYV28hL9nWgYcRlLJVwA7V4Ro XIzEtrlAvMe8SU1nDN+TTLbUF9Jv0kAOBK0uf/WcqRhLHdJ3fnm1fjNH6IyVV5j37ZbH IKnvFgpKB6Jb0ecXrjOMc/VuDJYeK+wVNks/6U28GleSvOVoiCQoCkJE0zVT0+/F2KCf vR1AMHYqjumz2LALhQKob6jv4FkpAgGZhJFj1Nk0OnebgUqh9J53aiYkKIkRc7RTq7NA sxGQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to:cc; bh=Udr2VC/34D/ej3jNtnHKlwamBndRUt0c7YEySUS9AYk=; b=O9PWUQryuvaS48G9091RbMGvTBQPWArAF+h5cylRX8L3cfPBEpMW28Qk33fTg+8pZz YJjYG/hYXGb/2G36l/xEW7DfvSmSdaWZ/FyNACbOC8CW+1dVbhqxZaKek9o9myqpppvW GmiZCVckdpcXdZQPLN3jmvkSTjJkH4eplPnTzvTSODkoPnaLAmXy88/NgvaHTSvnvDax aIgbzsYxdKnczy7csOh5XlBInouWrV9/5MO1/BJ16qW46qq/G1siQDq3rkEG6SfK8l7I lzEW3CPZBr1FuJZRGje6M0NSW/N72ZWVFH7ZZhIUWuatNcr9rzhrNJeY+SgQ2araIeWQ 8h2A== X-Gm-Message-State: APjAAAVIqXh9x/9QZtYZfkCpSvXnHT+J8E16/1CYhlXk6Fj/FtAoFNnj IhIL5sZyWEfEPGIJAqFmMLP/BwlKhQNYTfz+VPAcs+xP X-Google-Smtp-Source: APXvYqzMJzPVQb+2OubA1+n6rTS2XW/hj8N9D8QR/FDNAtBI9HFXoweWM3Vp0FVaLWgqUQHcuPVmsDt/qrVp2/AGKsY= X-Received: by 2002:a1c:3d07:: with SMTP id k7mr34811380wma.79.1578295519286; Sun, 05 Jan 2020 23:25:19 -0800 (PST) MIME-Version: 1.0 From: Sitsofe Wheeler Date: Mon, 6 Jan 2020 07:24:53 +0000 Message-ID: Subject: Questions about filesystems from SQLite author presentation To: linux-fsdevel@vger.kernel.org Cc: drh@sqlite.org Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org At Linux Plumbers 2019 Dr Richard Hipp presented a talk about SQLite (https://youtu.be/-oP2BOsMpdo?t=5525 ). One of the slides was titled "Things to discuss" (https://sqlite.org/lpc2019/doc/trunk/slides/sqlite-intro.html/#6 ) and had a few questions: 1. Reliable ways to discover detailed filesystem properties 2. fbarrier() 3. Notify the OS about unused regions in the database file For 1. I think Jan Kara said that supporting it was undesirable for details like just how much additional fsync were needed due to competing constraints (https://youtu.be/-oP2BOsMpdo?t=6063 ). Someone mentioned there was a patch for fsinfo to discover if you were on a network filesystem (https://www.youtube.com/watch?v=-oP2BOsMpdo&feature=youtu.be&t=5525 )... For 2. there was a talk by MySQL dev Sergei Golubchik ( https://youtu.be/-oP2BOsMpdo?t=1219 ) talking about how barriers had been taken out and was there a replacement. In https://youtu.be/-oP2BOsMpdo?t=1731 Chris Mason(?) seems to suggest that the desired effect could be achieved with io_uring chaining. For 3. it sounded like Jan Kara was saying there wasn't anything at the moment (hypothetically you could introduce a call that marked the extents as "unwritten" but it doesn't sound like you can do that today) and even if you wanted to use something like TRIM it wouldn't be worth it unless you were trimming a large (gigabytes) amount of data (https://youtu.be/-oP2BOsMpdo?t=6330 ). However, there were even more questions in the briefing paper (https://sqlite.org/lpc2019/doc/trunk/briefing.md and search for '?') that couldn't be asked due to limited time. Does anyone know the answer to the extended questions and whether the the above is right deduction for the questions that were asked? -- Sitsofe | http://sucs.org/~sits/