From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43352) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X2Awr-00083s-Ix for qemu-devel@nongnu.org; Tue, 01 Jul 2014 23:11:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1X2Awm-00051U-Ps for qemu-devel@nongnu.org; Tue, 01 Jul 2014 23:11:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5239) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X2Awm-00051O-HO for qemu-devel@nongnu.org; Tue, 01 Jul 2014 23:11:00 -0400 Message-ID: <53B37840.1020704@redhat.com> Date: Tue, 01 Jul 2014 21:10:56 -0600 From: Eric Blake MIME-Version: 1.0 References: <1404204537-5082-1-git-send-email-stefanha@redhat.com> <1404204537-5082-14-git-send-email-stefanha@redhat.com> In-Reply-To: <1404204537-5082-14-git-send-email-stefanha@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="sx73BTpDEdNwF4QD8etK2Gw1sc64B4eqP" Subject: Re: [Qemu-devel] [PULL for-2.1 13/24] qemu-img create: add 'nocow' option List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , qemu-devel@nongnu.org Cc: Peter Maydell , Chunyan Liu This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --sx73BTpDEdNwF4QD8etK2Gw1sc64B4eqP Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 07/01/2014 02:48 AM, Stefan Hajnoczi wrote: > From: Chunyan Liu >=20 > Add 'nocow' option so that users could have a chance to set NOCOW flag = to > newly created files. It's useful on btrfs file system to enhance perfor= mance. >=20 > Btrfs has low performance when hosting VM images, even more when the gu= est > in those VM are also using btrfs as file system. One way to mitigate th= is bad > performance is to turn off COW attributes on VM files. Generally, there= are > two ways to turn off NOCOW on btrfs: a) by mounting fs with nodatacow, = then > all newly created files will be NOCOW. b) per file. Add the NOCOW file > attribute. It could only be done to empty or new files. >=20 > This patch tries the second way, according to the option, it could add = NOCOW > per file. >=20 > For most block drivers, since the create file step is in raw-posix.c, s= o we > can do setting NOCOW flag ioctl in raw-posix.c only. >=20 > But there are some exceptions, like block/vpc.c and block/vdi.c, they a= re > creating file by calling qemu_open directly. For them, do the same sett= ing > NOCOW flag ioctl work in them separately. >=20 > [Fixed up 082.out due to the new 'nocow' creation option > --Stefan] >=20 > Signed-off-by: Chunyan Liu > Signed-off-by: Stefan Hajnoczi I see this is already in qemu.git, so it will need a followup to fix the user-visible typos (s/trun/turn/, s/Capitabl/Capital/) --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --sx73BTpDEdNwF4QD8etK2Gw1sc64B4eqP Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJTs3hAAAoJEKeha0olJ0NqFNAIAIxlbRTJZQDi3HfjNF4E+kt5 M1h27kKxnCBoABDk20lHYmfpCAUvMrKLhLjH8kT1YIgkDCF3cLFwuTuGrE3o0BzO 8itSazGiP6UQWLlD5KyunrDqrNFfIryqMofNBvi6JU7xH2ZL+wkB8qkvJM770CyO WnaXDkN6U/447q8I50vRI8ZVerMRC1nTWzmMZUq98w4pw3EmdylWyM1LJTTOzzvU vPLF8RX0LCz0aLcHV5mPcDVbLpfKx5qEDxvh6RWrV6nWM3nTdmPDwErFoM+X2ewj kBuQd6W0u3pNSye8qQzoyMQcrgmI4TO3hdENcWyUHgBscg25QsbNJIrO6g1HESM= =RMBm -----END PGP SIGNATURE----- --sx73BTpDEdNwF4QD8etK2Gw1sc64B4eqP--