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Tue, 10 Dec 2019 08:11:26 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-117-54.ams2.redhat.com [10.36.117.54]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 88A7A1001B07; Tue, 10 Dec 2019 08:11:21 +0000 (UTC) Subject: Re: [bugfix ping2] Re: [PATCH v2 0/2] fix qcow2_can_store_new_dirty_bitmap To: Eric Blake , Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" References: <20191014115126.15360-1-vsementsov@virtuozzo.com> <0db82122-ee0d-a346-cb49-d902d5d66b77@virtuozzo.com> <466a95d3-e808-02d1-94df-27bf1e4e13ee@redhat.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: Date: Tue, 10 Dec 2019 09:11:19 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <466a95d3-e808-02d1-94df-27bf1e4e13ee@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="n0EOPAf0aErje53jJ7YYwJ6CNGBiwTgFf" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 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" , "jsnow@redhat.com" , "qemu-devel@nongnu.org" , Denis Lunev 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) --n0EOPAf0aErje53jJ7YYwJ6CNGBiwTgFf Content-Type: multipart/mixed; boundary="TVuXtQjKQO0jZ7mpsqOmxcUo1JOt2Wrpn" --TVuXtQjKQO0jZ7mpsqOmxcUo1JOt2Wrpn Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 09.12.19 23:03, Eric Blake wrote: > On 12/9/19 11:58 AM, Max Reitz wrote: >> On 09.12.19 17:30, Max Reitz wrote: >>> On 02.12.19 15:09, Vladimir Sementsov-Ogievskiy wrote: >>>> Hi again! >>>> >>>> Still forgotten bug-fix :( >>>> >>>> Is it too late for 4.2? >>> >>> Sorry. :-/ >>> >>> Yes, I think I just forgot it.=C2=A0 I don=E2=80=99t think it=E2=80=99s= too important for >>> 4.2, so, well, it isn=E2=80=99t too bad, but...=C2=A0 Sorry. >>> >>>> I can't imagine better test, and it tests exactly what written in >>>> https://bugzilla.redhat.com/show_bug.cgi?id=3D1712636 >>>> >>>> (Hmm, actually, I doubt that it is real use-case, more probably it's >>>> a bug in management layer) >>>> >>>> So, take this with test or without test, to 4.2 or 5.0. >>> >>> I was thinking of seeing whether I could write a quicker test, but of >>> course we should take the patch either way. >> >> OK, I give up.=C2=A0 It=E2=80=99s very much possible to create an image = with 65535 >> bitmaps very quickly (like, under a second) outside of qemu, but just >> opening it takes 2:30 min (because of the quadratic complexity of >> checking whether a bitmap of the same name already exists). >=20 > Can we fix that to use a hash table for amortized O(1) lookup rather > than the current O(n) lookup? Not unreasonable, considering that this is probably what we would=E2=80=99v= e done from the start in any language where hash tables are built in. But OTOH when you have 66k bitmaps, you probably have other problems. Like, writes being incredibly slow, because all those bitmaps have to be updated. (Well, you can technically have 99 % of them disabled, but who=E2=80=99d do= such a thing?) ((Maybe I=E2=80=99ll look into it.)) Max --TVuXtQjKQO0jZ7mpsqOmxcUo1JOt2Wrpn-- --n0EOPAf0aErje53jJ7YYwJ6CNGBiwTgFf Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl3vUycACgkQ9AfbAGHV z0DWyAf/VjsDqKrMwQRPjfeH5xdfbL+r0XZMHm2YLa19QeodrFpLVi333wF+q1sA Um2g2gf8YXelcwSpN+RBZKPXtDJF/QMbeOSH7LZI62hhF+dD8vwS0Fr2YdHrxJKl 3SO3vZQ/7u5BCDYcneJqWfrY2gRz2ETS1VPLDV0qdCkh9/6Pe4/21bUKazYqTRKs 1o2Gf6pfvyYeKnr1+PlDPzpmxVOzfbspOa+Y04t6MpOxSA6m9LqpPiDUIb1+ykIa z9sy+dsNLHlKNkCwAXGOqWkvGzl5HF8WYCsG3g4LCYjbNC/aJPH+wXNrl1bc7hue nBTL1CTtcXP6qCfPJRWFX7y3k6g2Lw== =PMsB -----END PGP SIGNATURE----- --n0EOPAf0aErje53jJ7YYwJ6CNGBiwTgFf--