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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 CE829C433E0 for ; Fri, 19 Jun 2020 16:21:11 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 5E727217D8 for ; Fri, 19 Jun 2020 16:21:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TQh4XHEf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5E727217D8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33046 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jmJlO-0003pu-D9 for qemu-devel@archiver.kernel.org; Fri, 19 Jun 2020 12:21:10 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:45430) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jmJke-0003EE-4Z for qemu-devel@nongnu.org; Fri, 19 Jun 2020 12:20:24 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:52119 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jmJkc-0004FJ-I8 for qemu-devel@nongnu.org; Fri, 19 Jun 2020 12:20:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592583621; 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=emxUC3NDAznAQVfzo78UfVpFkpwG8HwWc5KpMv9LfCc=; b=TQh4XHEf+MGjHI0cCkEnxfQVKLphsE27LwWO7eZdWrzdLDwC/N8vWy1ev3upJOy3xnIE1E FKktWSyHieLAlIMMCZW0juwCjkYQHdQqr4c8OsF1QoEU1z2jBmPU7Q+WhO0YN8U6jdC2TX RZr6v5kEAiaKA6LgzLfrxWQqR+W94QM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-489-Ge0KtxYuOFKjymkKd1XiRg-1; Fri, 19 Jun 2020 12:20:17 -0400 X-MC-Unique: Ge0KtxYuOFKjymkKd1XiRg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 629EB872FEE; Fri, 19 Jun 2020 16:20:15 +0000 (UTC) Received: from localhost (ovpn-113-176.phx2.redhat.com [10.3.113.176]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4595879323; Fri, 19 Jun 2020 16:20:05 +0000 (UTC) Date: Fri, 19 Jun 2020 12:20:04 -0400 From: Eduardo Habkost To: "Denis V. Lunev" Subject: Re: [PATCH 0/2] block: propagate discard alignment from format drivers to the guest Message-ID: <20200619162004.GA9925@habkost.net> References: <20200611171608.22052-1-den@openvz.org> MIME-Version: 1.0 In-Reply-To: <20200611171608.22052-1-den@openvz.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/19 01:50:04 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Fam Zheng , qemu-block@nongnu.org, qemu-devel@nongnu.org, Max Reitz , Paolo Bonzini , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jun 11, 2020 at 08:16:06PM +0300, Denis V. Lunev wrote: > Nowaday SCSI drivers in guests are able to align UNMAP requests before > sending to the device. Right now QEMU provides an ability to set > this via "discard_granularity" property of the block device which could > be used by management layer. > > Though, in particular, from the point of QEMU, there is > pdiscard_granularity on the format driver level, f.e. on QCOW2 or iSCSI. > It would be beneficial to pass this value as a default for this > property. I assume the value is visible to the guest. What is supposed to happen if live migrating and the block backend is a different one on the destination? Also, don't we have mechanisms to change the block backend change at run time? What should happen in that case? > > Technically this should reduce the amount of use less UNMAP requests > from the guest to the host. Basic test confirms this. Fedora 31 guest > during 'fstrim /' on 32 Gb disk has issued 401/415 requests with/without > proper alignment to QEMU. > > Changes from v2: > - 172 iotest fixed > > Changes from v1: > - fixed typos in description > - added machine type compatibility layer as suggested by Kevin > > Signed-off-by: Denis V. Lunev > CC: Kevin Wolf > CC: Max Reitz > CC: Eduardo Habkost > CC: Marcel Apfelbaum > CC: John Snow > CC: Paolo Bonzini > CC: Fam Zheng > > -- Eduardo