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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 76D69C2BA83 for ; Thu, 13 Feb 2020 12:48:22 +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 41F952168B for ; Thu, 13 Feb 2020 12:48:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BYM+8I1w" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 41F952168B 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]:51616 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j2Dun-0003NY-FM for qemu-devel@archiver.kernel.org; Thu, 13 Feb 2020 07:48:21 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:43031) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j2Dtq-0002vc-Od for qemu-devel@nongnu.org; Thu, 13 Feb 2020 07:47:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j2Dto-0002B1-Ab for qemu-devel@nongnu.org; Thu, 13 Feb 2020 07:47:22 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:45183 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j2Dto-0002AE-6d for qemu-devel@nongnu.org; Thu, 13 Feb 2020 07:47:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581598038; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SrhUWHbuo2+hzsFW2k27Wzo8kufp8Phw+1/+5XPZwrQ=; b=BYM+8I1wCxnDFsDbchkCfUEGfzOjN5flk0VbuZq2CCbSCFSR7lgx15/t2T7biRB6Rvn94/ U+Cf7G6WfJUBXwuGYiNC13A1H/yDivybhPahUitVf96qaCd7ggZT4bd4AX4hcqBpDee8Au 9iTvpoYk0ZUT2gYU20Cm8phfaRF6Mww= 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-29-wv6dz4wTOUOIbU5GmvWOrg-1; Thu, 13 Feb 2020 07:47:13 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F22AA100550E; Thu, 13 Feb 2020 12:47:11 +0000 (UTC) Received: from [10.3.116.180] (ovpn-116-180.phx2.redhat.com [10.3.116.180]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4268126FCF; Thu, 13 Feb 2020 12:47:11 +0000 (UTC) Subject: Re: [PATCH] block: make BlockConf.*_size properties 32-bit To: Roman Kagan , qemu-devel@nongnu.org, Paolo Bonzini , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Eduardo Habkost , qemu-block@nongnu.org References: <20200211115401.43230-1-rvkagan@yandex-team.ru> <20200213080151.GA85593@rvkaganb> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Thu, 13 Feb 2020 06:47:10 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200213080151.GA85593@rvkaganb> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: wv6dz4wTOUOIbU5GmvWOrg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2/13/20 2:01 AM, Roman Kagan wrote: > On Wed, Feb 12, 2020 at 03:44:19PM -0600, Eric Blake wrote: >> On 2/11/20 5:54 AM, Roman Kagan wrote: >>> Devices (virtio-blk, scsi, etc.) and the block layer are happy to use >>> 32-bit for logical_block_size, physical_block_size, and min_io_size. >>> However, the properties in BlockConf are defined as uint16_t limiting >>> the values to 32768. >>> >>> This appears unnecessary tight, and we've seen bigger block sizes handy >>> at times. >> >> What larger sizes? I could see 64k or maybe even 1M block sizes,... > > We played exactly with these two :) > >>> >>> Make them 32 bit instead and lift the limitation. >>> >>> Signed-off-by: Roman Kagan >>> --- >>> hw/core/qdev-properties.c | 21 ++++++++++++--------- >>> include/hw/block/block.h | 8 ++++---- >>> include/hw/qdev-properties.h | 2 +- >>> 3 files changed, 17 insertions(+), 14 deletions(-) >>> >>> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c >>> index 7f93bfeb88..5f84e4a3b8 100644 >>> --- a/hw/core/qdev-properties.c >>> +++ b/hw/core/qdev-properties.c >>> @@ -716,30 +716,32 @@ const PropertyInfo qdev_prop_pci_devfn = { >>> /* --- blocksize --- */ >>> +#define MIN_BLOCK_SIZE 512 >>> +#define MAX_BLOCK_SIZE 2147483648 >> >> ...but 2G block sizes are going to have tremendous performance problems. >> >> I'm not necessarily opposed to the widening to a 32-bit type, but think you >> need more justification or a smaller number for the max block size, > > I thought any smaller value would just be arbitrary and hard to reason > about, so I went ahead with the max value that fit in the type and could > be made visibile to the guest. You've got bigger problems than what is visible to the guest. block/qcow2.c operates on a cluster at a time; if you are stating that it now requires reading multiple clusters to operate on one, qcow2 will have to do lots of wasteful read-modify-write cycles. You really need a strong reason to support a maximum larger than 2M other than just "so the guest can experiment with it". > > Besides this is a property that is set explicitly, so I don't see a > problem leaving this up to the user. > >> particularly since qcow2 refuses to use cluster sizes larger than 2M and it >> makes no sense to allow a block size larger than a cluster size. > > This still doesn't contradict passing a bigger value to the guest, for > experimenting if nothing else. > > Thanks, > Roman. > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org