On 07/01/2014 02:48 AM, Stefan Hajnoczi wrote: > From: Chunyan Liu <cy...@suse.com> > > 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 performance. > > Btrfs has low performance when hosting VM images, even more when the guest > in those VM are also using btrfs as file system. One way to mitigate this 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. > > This patch tries the second way, according to the option, it could add NOCOW > per file. > > For most block drivers, since the create file step is in raw-posix.c, so we > can do setting NOCOW flag ioctl in raw-posix.c only. > > But there are some exceptions, like block/vpc.c and block/vdi.c, they are > creating file by calling qemu_open directly. For them, do the same setting > NOCOW flag ioctl work in them separately. > > [Fixed up 082.out due to the new 'nocow' creation option > --Stefan] > > Signed-off-by: Chunyan Liu <cy...@suse.com> > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
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/) -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature
