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Mon, 5 Aug 2019 13:49:30 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.217]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 432495D71A; Mon, 5 Aug 2019 13:49:28 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" References: <20190805114923.23701-1-mreitz@redhat.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: Date: Mon, 5 Aug 2019 15:49:26 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="xrc8YTn7kq0pmcnj1WzGCgpQm4ea7ZJcD" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 05 Aug 2019 13:49:31 +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 Subject: Re: [Qemu-devel] [PATCH] mirror: Only mirror granularity-aligned chunks 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 , John Snow , "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) --xrc8YTn7kq0pmcnj1WzGCgpQm4ea7ZJcD Content-Type: multipart/mixed; boundary="bBZrVvUeQ6upwtaJnlL3JsKIL2tCHFTkh"; protected-headers="v1" From: Max Reitz To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" Cc: "qemu-devel@nongnu.org" , John Snow , Kevin Wolf Message-ID: Subject: Re: [PATCH] mirror: Only mirror granularity-aligned chunks References: <20190805114923.23701-1-mreitz@redhat.com> In-Reply-To: --bBZrVvUeQ6upwtaJnlL3JsKIL2tCHFTkh Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 05.08.19 15:00, Vladimir Sementsov-Ogievskiy wrote: > 05.08.2019 14:49, Max Reitz wrote: >> In write-blocking mode, all writes to the top node directly go to the >> target. We must only mirror chunks of data that are aligned to the >> job's granularity, because that is how the dirty bitmap works. >> Therefore, the request alignment for writes must be the job's >> granularity (in write-blocking mode). >> >> Unfortunately, this forces all reads and writes to have the same >> granularity (we only need this alignment for writes to the target, not= >> the source), but that is something to be fixed another time. >> >> Signed-off-by: Max Reitz >> --- >> This is an alternative to Vladimir's "util/hbitmap: fix unaligned rese= t" >> patch. I don't mind much either way, both of pros and cons. Comparin= g >> this patch to Vladimir's: >> >> + Makes copy-mode=3Dwrite-blocking really work (unless I'm mistaken) >> - Lowers performance with copy-mode=3Dwrite-blocking unnecessarily >> --- >> block/mirror.c | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/block/mirror.c b/block/mirror.c >> index 8cb75fb409..3f9c5a178a 100644 >> --- a/block/mirror.c >> +++ b/block/mirror.c >> @@ -1481,6 +1481,15 @@ static void bdrv_mirror_top_child_perm(BlockDri= verState *bs, BdrvChild *c, >> *nshared =3D BLK_PERM_ALL; >> } >> =20 >> +static void bdrv_mirror_top_refresh_limits(BlockDriverState *bs, Erro= r **errp) >> +{ >> + MirrorBDSOpaque *s =3D bs->opaque; >> + >> + if (s && s->job && s->job->copy_mode =3D=3D MIRROR_COPY_MODE_WRIT= E_BLOCKING) { >> + bs->bl.request_alignment =3D s->job->granularity; >> + } >> +} >> + >> /* Dummy node that provides consistent read to its users without req= uiring it >> * from its backing file and that allows writes on the backing file = chain. */ >> static BlockDriver bdrv_mirror_top =3D { >> @@ -1493,6 +1502,7 @@ static BlockDriver bdrv_mirror_top =3D { >> .bdrv_co_block_status =3D bdrv_co_block_status_from_backin= g, >> .bdrv_refresh_filename =3D bdrv_mirror_top_refresh_filename= , >> .bdrv_child_perm =3D bdrv_mirror_top_child_perm, >> + .bdrv_refresh_limits =3D bdrv_mirror_top_refresh_limits, >> }; >> =20 >> static BlockJob *mirror_start_job( >> @@ -1678,6 +1688,8 @@ static BlockJob *mirror_start_job( >> =20 >> QTAILQ_INIT(&s->ops_in_flight); >> =20 >> + bdrv_refresh_limits(mirror_top_bs, &error_abort); >> + >> trace_mirror_start(bs, s, opaque); >> job_start(&s->common.job); >> =20 >> >=20 > Am I right that the fact that no guest request will skip this limit is = guaranteed by > aio_context_acquire/release around blockdev_mirror_common? Hm. As long as we don=E2=80=99t drain or release the context. Unfortunately, block_job_add_bdrv() does release the context (if the job runs in a foreign context). The reason we need this call is because the automatic calls invoke the function when either bs->opaque or bs->opaque->job are still NULL, or when bs->opaque->job->copy_mode is not yet set. So I could just call it when copy_mode has been set (which is still before the dirty bitmap is created; and if we have I/O before that point, we have bigger problems than this.) Max > Not sure how much it lowers performance, but it should work.. > Reviewed-by: Vladimir Sementsov-Ogievskiy >=20 --bBZrVvUeQ6upwtaJnlL3JsKIL2tCHFTkh-- --xrc8YTn7kq0pmcnj1WzGCgpQm4ea7ZJcD Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl1IM+YACgkQ9AfbAGHV z0Be+Qf/RA5rsOGqxFzowfi9k9OjE+5IU9MJVDk9adaPAR3pKJM/uBpw/Loe2EEV HP0DNunOc3Othkgg22Oqqzkx91yWriFnFMVvLFS6m+JSoepc2RAPaCLJYdXe517q Z7lgCSMSesRWaz9NFSiNwWgCfK42DMRm/CCrZxC9scppsETT37+Zt505lkK6k0uO mA1l8EpPQ4bCEwxxWqC3992KmlnfLrfDHc5JE6ObOowHUWxgB2Fjoa4J0iSnUcWI hmXjTR7q7hyDRoh45aR+FWyeOYSk5AnXulOeiSIpCMwkr1wD3rF3puODJ/iyhaS6 dH/P4RZbCd4eBul5CO4u58V+RnABIg== =1uz5 -----END PGP SIGNATURE----- --xrc8YTn7kq0pmcnj1WzGCgpQm4ea7ZJcD--