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Thu, 30 Apr 2020 11:47:12 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-112-177.ams2.redhat.com [10.36.112.177]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 228076116D; Thu, 30 Apr 2020 11:47:08 +0000 (UTC) Subject: Re: [PATCH v22 3/4] qcow2: add zstd cluster compression To: Denis Plotnikov , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org References: <20200428200013.24474-1-dplotnikov@virtuozzo.com> <20200428200013.24474-4-dplotnikov@virtuozzo.com> <23f0a79a-6e8d-3702-3d82-9db54a442a5f@virtuozzo.com> <73ebc101-7148-2b38-492f-538d4bf8c8a4@redhat.com> <477e76fd-ff73-ac34-c636-c8d9ae6be30d@virtuozzo.com> From: Max Reitz 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: <22b2918b-3bdd-6627-a378-baddb342dacc@redhat.com> Date: Thu, 30 Apr 2020 13:47:06 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <477e76fd-ff73-ac34-c636-c8d9ae6be30d@virtuozzo.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="yJ9xrMdXPTBrXfWJPiAYLAsmu8YKpdZGf" Received-SPF: pass client-ip=205.139.110.61; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/30 01:04:40 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: kwolf@redhat.com, berto@igalia.com, qemu-block@nongnu.org, armbru@redhat.com, den@openvz.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) --yJ9xrMdXPTBrXfWJPiAYLAsmu8YKpdZGf Content-Type: multipart/mixed; boundary="tI3Z0CANqtQ2ImVb74zjsIkYcoYEpkpSW" --tI3Z0CANqtQ2ImVb74zjsIkYcoYEpkpSW Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 30.04.20 11:48, Denis Plotnikov wrote: >=20 >=20 > On 30.04.2020 11:26, Max Reitz wrote: >> On 29.04.20 15:02, Vladimir Sementsov-Ogievskiy wrote: >>> 29.04.2020 15:17, Max Reitz wrote: >>>> On 29.04.20 12:37, Vladimir Sementsov-Ogievskiy wrote: >>>>> 29.04.2020 13:24, Max Reitz wrote: >>>>>> On 28.04.20 22:00, Denis Plotnikov wrote: >>>>>>> zstd significantly reduces cluster compression time. >>>>>>> It provides better compression performance maintaining >>>>>>> the same level of the compression ratio in comparison with >>>>>>> zlib, which, at the moment, is the only compression >>>>>>> method available. >>>>>>> >>>>>>> The performance test results: >>>>>>> Test compresses and decompresses qemu qcow2 image with just >>>>>>> installed rhel-7.6 guest. >>>>>>> Image cluster size: 64K. Image on disk size: 2.2G >>>>>>> >>>>>>> The test was conducted with brd disk to reduce the influence >>>>>>> of disk subsystem to the test results. >>>>>>> The results is given in seconds. >>>>>>> >>>>>>> compress cmd: >>>>>>> =A0=A0=A0=A0 time ./qemu-img convert -O qcow2 -c -o >>>>>>> compression_type=3D[zlib|zstd] >>>>>>> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 src.im= g [zlib|zstd]_compressed.img >>>>>>> decompress cmd >>>>>>> =A0=A0=A0=A0 time ./qemu-img convert -O qcow2 >>>>>>> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 [zlib|= zstd]_compressed.img uncompressed.img >>>>>>> >>>>>>> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 compression=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0 decompression >>>>>>> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 zlib=A0=A0=A0=A0=A0=A0 zstd=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0 zlib=A0=A0=A0=A0=A0=A0=A0=A0 zstd >>>>>>> ------------------------------------------------------------ >>>>>>> real=A0=A0=A0=A0 65.5=A0=A0=A0=A0=A0=A0 16.3 (-75 %)=A0=A0=A0 1.9= =A0=A0=A0=A0=A0=A0=A0=A0=A0 1.6 (-16 %) >>>>>>> user=A0=A0=A0=A0 65.0=A0=A0=A0=A0=A0=A0 15.8=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0 5.3=A0=A0=A0=A0=A0=A0=A0=A0=A0 2.5 >>>>>>> sys=A0=A0=A0=A0=A0=A0 3.3=A0=A0=A0=A0=A0=A0=A0 0.2=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0 2.0=A0=A0=A0=A0=A0=A0=A0=A0=A0 2.0 >>>>>>> >>>>>>> Both ZLIB and ZSTD gave the same compression ratio: 1.57 >>>>>>> compressed image size in both cases: 1.4G >>>>>>> >>>>>>> Signed-off-by: Denis Plotnikov >>>>>>> QAPI part: >>>>>>> Acked-by: Markus Armbruster >>>>>>> --- >>>>>>> =A0=A0=A0 docs/interop/qcow2.txt |=A0=A0 1 + >>>>>>> =A0=A0=A0 configure=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 |=A0=A0 = 2 +- >>>>>>> =A0=A0=A0 qapi/block-core.json=A0=A0 |=A0=A0 3 +- >>>>>>> =A0=A0=A0 block/qcow2-threads.c=A0 | 169 >>>>>>> +++++++++++++++++++++++++++++++++++++++++ >>>>>>> =A0=A0=A0 block/qcow2.c=A0=A0=A0=A0=A0=A0=A0=A0=A0 |=A0=A0 7 ++ >>>>>>> =A0=A0=A0 slirp=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 = |=A0=A0 2 +- >>>>>>> =A0=A0=A0 6 files changed, 181 insertions(+), 3 deletions(-) >>>>>> [...] >>>>>> >>>>>>> diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c >>>>>>> index 7dbaf53489..a0b12e1b15 100644 >>>>>>> --- a/block/qcow2-threads.c >>>>>>> +++ b/block/qcow2-threads.c >>>>>> [...] >>>>>> >>>>>>> +static ssize_t qcow2_zstd_decompress(void *dest, size_t dest_size, >>>>>>> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 const void *src, size_t >>>>>>> src_size) >>>>>>> +{ >>>>>> [...] >>>>>> >>>>>>> +=A0=A0=A0 /* >>>>>>> +=A0=A0=A0=A0 * The compressed stream from the input buffer may con= sist of >>>>>>> more >>>>>>> +=A0=A0=A0=A0 * than one zstd frame. >>>>>> Can it? >>>>> If not, we must require it in the specification. >>>> Actually, now that you mention it, it would make sense anyway to add >>>> some note to the specification on what exactly compressed with zstd >>>> means. >>>> >>>>> Hmm. If at some point >>>>> we'll want multi-threaded compression of one big (2M) cluster.. Could >>>>> this be implemented with zstd lib, if multiple frames are allowed, >>>>> will >>>>> allowing multiple frames help? I don't know actually, but I think >>>>> better >>>>> not to forbid it. On the other hand, I don't see any benefit in large >>>>> compressed clusters. At least, in our scenarios (for compressed >>>>> backups) >>>>> we use 64k compressed clusters, for good granularity of incremental >>>>> backups (when for running vm we use 1M clusters). >>>> Is it really that important?=A0 Na=EFvely, it sounds rather complicate= d to >>>> introduce multithreading into block drivers. >>> It is already here: compression and encryption already multithreaded. >>> But of course, one cluster is handled in one thread. >> Ah, good.=A0 I forgot. >> >>>> (Also, as for compression, it can only be used in backup scenarios >>>> anyway, where you write many clusters at once.=A0 So parallelism on th= e >>>> cluster level should sufficient to get high usage, and it would benefi= t >>>> all compression types and cluster sizes.) >>>> >>> Yes it works in this way already :) >> Well, OK then. >> >>> So, we don't know do we want one frame restriction or not. Do you have = a >>> preference? >> *shrug* >> >> Seems like it would be preferential to allow multiple frames still.=A0 A >> note in the spec would be nice (i.e., streaming format, multiple frames >> per cluster possible). >=20 > We don't mention anything about zlib compressing details in the spec. Yep. Which is bad enough. > If we mention anything about ZSTD compressing details we'll have to do > it for > zlib as well. I personally don=92t like =93If you can=92t make it perfect, you shouldn=92= t do it at all=94. Mentioning it for zstd would still be an improvement. Also, I believe that =93zlib compression=94 is pretty much unambiguous, considering all the code does is call deflate()/inflate(). I=92m not saying we need to amend the spec in this series, but I don=92t se= e a good argument against doing so at some point. > So, I think we have two possibilities for the spec: > 1. mention for both > 2. don't mention at all >=20 > I think the 2nd is better. It gives more degree of freedom for the > future improvements. No, it absolutely doesn=92t. There is a de-facto format, namely what qemu accepts. Changing that would be an incompatible change. Just because we don=92t write what=92s allowed into the spec doesn=92t change that fact. > and we've already covered both cases (one frame, may frames) in the code. There are still different zstd formats, namely streaming or not streaming. That=92s what should be mentioned. Max --tI3Z0CANqtQ2ImVb74zjsIkYcoYEpkpSW-- --yJ9xrMdXPTBrXfWJPiAYLAsmu8YKpdZGf Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl6quroACgkQ9AfbAGHV z0B9xAf/cFGRpm6MM44I/c1AvmlRqsCOc3xdhcUS8EC5fdlzsPhltfuj1rjIomVT R/PfYypRtw7vqBKbeTYs7ov0BPqDNR0jii82iDQiuaJcwiWRSycdx6sJ5gGy4Suy rzGwkJybn16JX5PceR4/tWScdPsVkDn+dqL0BRg/6SKmxiiMswkZBnjNbu4BJF7N eMxAO6+j7k3d1WzF6YO7Mg+IZpxG5RjEQxlwf9ibL/yRwfFsO9eYjGEHaNe2ZvwF 5h4p20SLtZ9ihLmL8ZCMMInWcK5Al76S8vrD/s8ekk21OPMkLMOuBXXDqwKfPUXR g/WL/VaPPR5aMBbaVK3RzFJJBiAccQ== =1oY7 -----END PGP SIGNATURE----- --yJ9xrMdXPTBrXfWJPiAYLAsmu8YKpdZGf--