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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA16FC04A68 for ; Wed, 27 Jul 2022 14:50:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234228AbiG0Ou1 (ORCPT ); Wed, 27 Jul 2022 10:50:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232508AbiG0OuZ (ORCPT ); Wed, 27 Jul 2022 10:50:25 -0400 Received: from new4-smtp.messagingengine.com (new4-smtp.messagingengine.com [66.111.4.230]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50AC933A19 for ; Wed, 27 Jul 2022 07:50:24 -0700 (PDT) Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailnew.nyi.internal (Postfix) with ESMTP id E5C1A580457; Wed, 27 Jul 2022 10:50:21 -0400 (EDT) Received: from imap50 ([10.202.2.100]) by compute3.internal (MEProxy); Wed, 27 Jul 2022 10:50:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= colorremedies.com; h=cc:cc:content-type:date:date:from:from :in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:sender:subject:subject:to:to; s=fm1; t=1658933421; x= 1658937021; bh=r+rbiVADTbAb9ADIG7wtCzU3eu5fVv94D3nnS3Tsz9Y=; b=S qaApFKZ3dCB7Fe2i06qFjERkPJ2p1W8ltAOgA/GahkzudHDlflb45fXoa8qiWGx5 LVPhiJbJ2aEcpA4fLb+Q2ZIT/RhonLTo3dYJ0leeBaLo8VizZZMldFTHAPYhoqRq zRHskwhYhYAyVMt+seWNu9fzSDGnU+xg1IJP7dbf5a7LY57X8k0YcFqDWxaNKD+J SxouN0uWYU/B9v4F5aVfUWRjDunOS0DSLn0q5xhCNwtH29KrLgiLrgowVSSGOiXc 3s/2i1+desJmcR2Lbm6jx0ZW1pXXGCS3fYoGwbw5es0dukHZFkD62MNJ97djSzVU kz1kNPS5cwHFu5vYSkBAQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:date:date:feedback-id :feedback-id:from:from:in-reply-to:in-reply-to:message-id :mime-version:references:reply-to:sender:subject:subject:to:to :x-me-proxy:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s= fm3; t=1658933421; x=1658937021; bh=r+rbiVADTbAb9ADIG7wtCzU3eu5f Vv94D3nnS3Tsz9Y=; b=F9dACI5Dxo3C69FbtzMkKPGxfOo73j6/0P27OBJ+jkYz FIhVZZQ4WkG+8NM6RcJ0okQYRM+pMelwo6eVUTrcVIXpCcI27w3bB3wHq1EIvdIy 9yK4gpK247yPi9/ixcg9jFnhlDie2+nBXJ89v0jGex7MuDwgUV2ilQOx0pLIIa3l B9Wz4ScQ5PUUt1NrGjbbE25xsH3apJ/oAb4twSNav6qJkEzhzMcObdg9+uaX3o5S Wseu776GwxARyqJ5mx9xEgVpnADSKybExKPBbeH/YVlZSDjgkhB7OXu3X+JTTHP5 JFfQ3L4AChg6oMwRvuy92L2ZWBOrf1kUkueyKz+i4Q== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvfedrvdduvddgkeduucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepofgfggfkjghffffhvfevufgtsehttdertderredtnecuhfhrohhmpedfvehh rhhishcuofhurhhphhihfdcuoehlihhsthhssegtohhlohhrrhgvmhgvughivghsrdgtoh hmqeenucggtffrrghtthgvrhhnpefgvdeukedtfefgfefgtdelffdvieeltefgfedutdff leeuieevieevkeehtdehueenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmh grihhlfhhrohhmpehlihhsthhssegtohhlohhrrhgvmhgvughivghsrdgtohhm X-ME-Proxy: Feedback-ID: i06494636:Fastmail Received: by mailuser.nyi.internal (Postfix, from userid 501) id 73DDC1700082; Wed, 27 Jul 2022 10:50:21 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.7.0-alpha0-757-gc3ad9c75d3-fm-20220722.001-gc3ad9c75 Mime-Version: 1.0 Message-Id: <68dc27f3-32a8-4a2a-bfcc-0cf26bca8fec@www.fastmail.com> In-Reply-To: References: <20220725190811.GD13489@twin.jikos.cz> <336b3dc2-2ca9-4f14-ad45-1896b36e0e82@www.fastmail.com> <20220726213628.GO13489@twin.jikos.cz> Date: Wed, 27 Jul 2022 10:50:01 -0400 From: "Chris Murphy" To: "David Sterba" Cc: "Neal Gompa" , "Btrfs BTRFS" , "Chris Mason" , "Josef Bacik" Subject: Re: Using async discard by default with SSDs? Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Tue, Jul 26, 2022, at 6:10 PM, Chris Murphy wrote: > On Tue, Jul 26, 2022, at 5:36 PM, David Sterba wrote: >> What is quickly here? > > Seconds, less than a minute, all the blocks pointed to by backup roots > are empty (zeros). > > The default timeout is set to 2 minutes and that's >> what I've seen when testing that on a fresh filesystem. > > Ok I'll retest with 5.19 series. The last time I tested time to drive > gc backup rootswas circa 5.8. With 5.19, backup roots remain available for a surprisingly long time, definitely more than 2 minutes. It's not an exhaustive test, just a dozen samples over a half hour, but I never once saw zeros returned. Two out of those dozen, I saw the block already overwritten with a leaf of a newer generation and a completely different owner (e.g. csum tree written at the block address for the backup tree root) - which would make that backup root useless. What is a likely target kernel version to make discard=async the default? The merge window for 5.20 closes August 14. Is 5.21 a practical target? -- Chris Murphy