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=-1.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,UNPARSEABLE_RELAY autolearn=unavailable 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 2C775C43381 for ; Fri, 22 Feb 2019 02:51:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 00A0520836 for ; Fri, 22 Feb 2019 02:51:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="Kc29hitp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726318AbfBVCvX (ORCPT ); Thu, 21 Feb 2019 21:51:23 -0500 Received: from userp2130.oracle.com ([156.151.31.86]:58742 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725869AbfBVCvX (ORCPT ); Thu, 21 Feb 2019 21:51:23 -0500 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x1M2nNDu007607; Fri, 22 Feb 2019 02:51:17 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=to : cc : subject : from : references : date : in-reply-to : message-id : mime-version : content-type; s=corp-2018-07-02; bh=EEHFAbiLOwsLyMMd+WQLEdd04j4914veZ/6J2sA/06E=; b=Kc29hitp9ohY1v2DLIA+uUTB8d8oyOwVsbqCk7YXkyTnSs8cGwKALessg6me0P7tiaJd Bcs9UX+6yOhQ88483ltt5cNBaHo+YEuD+Du1tBioLgiAdaQgluaM9TI8JXVdFZ1Z+0cP 1jWq6iNPDJbvcxGwkmHP4ZQSv4zHQA/pDkwKz8yFZJN96qGn58utvYJscxb6hhTAEVak dI6xBaTucjEVWnwgnnG2kMT9HEp6dJwGrC2rs/NBfL4l4znTpETLEY24i8V33+bzmc1Z XVubS0DK4wrJhDHdYZxXfrzLNSuFDStPwilUEN5NfIXlEdD0Kce2/+j2E2cKJYI1q7Dk Lw== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by userp2130.oracle.com with ESMTP id 2qp9xubxr8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 22 Feb 2019 02:51:16 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x1M2pGqn001612 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 22 Feb 2019 02:51:16 GMT Received: from abhmp0020.oracle.com (abhmp0020.oracle.com [141.146.116.26]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x1M2pFrf017944; Fri, 22 Feb 2019 02:51:15 GMT Received: from ca-mkp.ca.oracle.com (/10.159.214.123) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 21 Feb 2019 18:51:15 -0800 To: Keith Busch Cc: Ric Wheeler , Dave Chinner , lsf-pc@lists.linux-foundation.org, linux-xfs , linux-fsdevel , linux-ext4 , linux-btrfs , linux-block@vger.kernel.org Subject: Re: [LSF/MM TOPIC] More async operations for file systems - async discard? From: "Martin K. Petersen" Organization: Oracle Corporation References: <92ab41f7-35bc-0f56-056f-ed88526b8ea4@gmail.com> <20190217210948.GB14116@dastard> <46540876-c222-0889-ddce-44815dcaad04@gmail.com> <20190220234723.GA5999@localhost.localdomain> Date: Thu, 21 Feb 2019 21:51:12 -0500 In-Reply-To: <20190220234723.GA5999@localhost.localdomain> (Keith Busch's message of "Wed, 20 Feb 2019 16:47:24 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9174 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=723 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902220016 Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Keith, > With respect to fs block sizes, one thing making discards suck is that > many high capacity SSDs' physical page sizes are larger than the fs > block size, and a sub-page discard is worse than doing nothing. That ties into the whole zeroing as a side-effect thing. The devices really need to distinguish between discard-as-a-hint where it is free to ignore anything that's not a whole multiple of whatever the internal granularity is, and the WRITE ZEROES use case where the end result needs to be deterministic. -- Martin K. Petersen Oracle Linux Engineering