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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 65BC1C04AB3 for ; Mon, 27 May 2019 13:52:22 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2CC7F20675 for ; Mon, 27 May 2019 13:52:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2CC7F20675 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 ([127.0.0.1]:46268 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVG33-0004SI-60 for qemu-devel@archiver.kernel.org; Mon, 27 May 2019 09:52:21 -0400 Received: from eggs.gnu.org ([209.51.188.92]:38807) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVG2B-00048z-KJ for qemu-devel@nongnu.org; Mon, 27 May 2019 09:51:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hVG29-0002jR-NG for qemu-devel@nongnu.org; Mon, 27 May 2019 09:51:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46126) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hVG26-0002gA-Ra; Mon, 27 May 2019 09:51:23 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 1705E308FF2C; Mon, 27 May 2019 13:51:18 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.13]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4AEB07BE99; Mon, 27 May 2019 13:51:16 +0000 (UTC) To: Anton Nefedov , Alberto Garcia , "qemu-block@nongnu.org" References: <20190524172812.27308-1-mreitz@redhat.com> <20190524172812.27308-2-mreitz@redhat.com> <66e86c16-c30c-5363-ef94-f01da8979872@redhat.com> <92b7c22d-06bb-f04a-0df1-7340c11be954@redhat.com> <80167166-a23a-6f10-c28b-a3a905f7ca6e@virtuozzo.com> From: Max Reitz Openpgp: preference=signencrypt Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: <6df6e5e7-2d42-2e71-b887-56c091413232@redhat.com> Date: Mon, 27 May 2019 15:51:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <80167166-a23a-6f10-c28b-a3a905f7ca6e@virtuozzo.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="zhvKhCwMelUKxxyP4fkwz5GcmAis1ME3O" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Mon, 27 May 2019 13:51:21 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 X-Content-Filtered-By: Mailman/MimeDel 2.1.21 Subject: Re: [Qemu-devel] [RFC 1/3] block: Add ImageRotationalInfo X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --zhvKhCwMelUKxxyP4fkwz5GcmAis1ME3O From: Max Reitz To: Anton Nefedov , Alberto Garcia , "qemu-block@nongnu.org" Cc: "qemu-devel@nongnu.org" , Kevin Wolf , Vladimir Sementsov-Ogievskiy Message-ID: <6df6e5e7-2d42-2e71-b887-56c091413232@redhat.com> Subject: Re: [RFC 1/3] block: Add ImageRotationalInfo References: <20190524172812.27308-1-mreitz@redhat.com> <20190524172812.27308-2-mreitz@redhat.com> <66e86c16-c30c-5363-ef94-f01da8979872@redhat.com> <92b7c22d-06bb-f04a-0df1-7340c11be954@redhat.com> <80167166-a23a-6f10-c28b-a3a905f7ca6e@virtuozzo.com> In-Reply-To: <80167166-a23a-6f10-c28b-a3a905f7ca6e@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 27.05.19 15:44, Anton Nefedov wrote: > On 27/5/2019 3:57 PM, Max Reitz wrote: >> On 27.05.19 14:37, Alberto Garcia wrote: >>> On Mon 27 May 2019 02:16:53 PM CEST, Max Reitz wrote: >>>> On 26.05.19 17:08, Alberto Garcia wrote: >>>>> On Fri 24 May 2019 07:28:10 PM CEST, Max Reitz = wrote: >>>>>> +## >>>>>> +# @ImageRotationalInfo: >>>>>> +# >>>>>> +# Indicates whether an image is stored on a rotating disk or not.= >>>>>> +# >>>>>> +# @solid-state: Image is stored on a solid-state drive >>>>>> +# >>>>>> +# @rotating: Image is stored on a rotating disk >>>>> >>>>> What happens when you cannot tell? You assume it's solid-state? >>>> >>>> When *I* cannot tell? This field is generally optional, so in that = case >>>> it just will not be present. >>>> >>>> (When Linux cannot tell? I don=E2=80=99t know :-)) >>>> >=20 > Linux defaults to rotational =3D=3D 1 unless the driver sets > QUEUE_FLAG_NONROT. >=20 > By the way as far as I can tell, qemu does not report this flag unless > explicitly set in a device property. >=20 > DEFINE_PROP_UINT16("rotation_rate", IDEDrive, dev.rotation_rate, 0= ), > and > DEFINE_PROP_UINT16("rotation_rate", SCSIDiskState, rotation_rate, = 0), >=20 >>>> Do you think there should be an explicit value for that? >>> >>> I'll try to rephrase: >>> >>> we have a new optimization that improves performance on SSDs but redu= ces >>> performance on HDDs, so this series would detect where an image is >>> stored in order to enable the faster code path for each case. >>> >>> What happens if QEMU cannot detect if we have a solid drive or a >>> rotational drive? (e.g. a remote storage backend). Will it default to= >>> enabling preallocation using write_zeroes()? >> >> In this series, yes. That is the default I chose. >> >> We have to make a separate decision for each case. In the case of >> filling newly allocated areas with zeroes, I think the performance gai= n >> for SSDs is more important than the performance loss for HDDs. That i= s >> what I wrote in my response to Anton=E2=80=99s series. So I took the = series >> even without it being able to distinguish both cases at all. >> Consequentially, I believe it is reasonable for that to be the default= >> behavior if we cannot tell. >> >> I think in general optimizing for SSDs should probably be the default.= >> HDDs are slow anyway, so whoever uses them probably doesn=E2=80=99t ca= re about >> performance too much anyway...? Whereas people using SSDs probably do= =2E >> But as I said, we can and should always make a separate decision for= >> each case. >> >=20 > Overall it looks good to me but I wonder how do we ensure both variants= > are test covered? Need a blockdev option to enforce the mode? That=E2=80=99s a good point. Yes, file-posix should probably take an opt= ion to override the mode. Actually, that may be a useful option in general (if the file is on some file system where we cannot query this information (like glusterfs), the user may want to manually provide it). Max --zhvKhCwMelUKxxyP4fkwz5GcmAis1ME3O Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAlzr61IACgkQ9AfbAGHV z0DCoAgAqMo7Df0ZNXKQZTpMbO1PeOj7+kKPmX8i/6QKZEXzPZ3uE9UKwjwLVdnI 4Ospo/nWvLnVwW6a+4d3DanzpvsQY6j7lTW3oBd4PpwMBTLnnv2Ptoh0Pl6t/EI1 mDpE78QxSwJw//d6XOPZWcOj4i8zDbEK1OJhxYqkyAtKbgATfXIz9zjZ/Z8avJkY qyu38yUNw185z18qPT1ZFajOW2XpGLn+NfxWg6HiXOt3kuNcH0l3kcEjOPKSbDJ8 UaWTrzZOxsDHOXIYClGBwy9j9hw7EIf3FGcBD27/PIGPt/slxF9tSSSQXZUnicJA FGskyZoaVyklPXrtCNwcoOShwNan+A== =ezG2 -----END PGP SIGNATURE----- --zhvKhCwMelUKxxyP4fkwz5GcmAis1ME3O--