On Fri, Feb 08, 2013 at 02:06:10PM +0100, Paolo Bonzini wrote: > The major missing step in order to implement thin provisioning is > exposing discard commands to the guest. This series implements > minimal control of this capability. > > Whether to enable discard or not is made a host parameter, so that > choices in storage technology do not affect the hardware that the > guest sees. While it is still possible to fine-tune the parameters > (at least for SCSI disks), the default granularity is set to the > logical block size or 4k, whichever is largest, because cluster > sizes below 4k are rarely used and 4K is a typical block size > for files. > > Nevertheless, using DISCARD with filesystems can cause very severe > fragmentation, so it is left default-off for now. This can change later > when we implement the "anchor" operation for efficient management of > preallocated files. > > Paolo > > > Paolo Bonzini (5): > block: implement BDRV_O_UNMAP > blockdev: add discard suboption to -drive > qemu-nbd: add --discard option > blockdev: enable discard by default > pc: add compatibility machine types for 1.4 > > block.c | 25 +++++++++++++++++++++++++ > blockdev.c | 11 +++++++++++ > hw/block-common.h | 2 +- > hw/ide/qdev.c | 5 ++++- > hw/pc.h | 32 ++++++++++++++++++++++++++++++++ > hw/pc_piix.c | 18 ++++++++++++++++-- > hw/pc_q35.c | 19 ++++++++++++++++--- > hw/scsi-disk.c | 13 ++++++++++--- > include/block/block.h | 2 ++ > qemu-io.c | 11 +++++++++-- > qemu-nbd.c | 18 +++++++++++++++--- > qemu-nbd.texi | 4 ++++ > qemu-options.hx | 2 ++ > 13 files changed, 147 insertions(+), 15 deletions(-) > > -- > 1.8.1.2 > >
I posted one comment, otherwise looks good.
