Am 02.07.2013 um 13:04 schrieb Paolo Bonzini <pbonz...@redhat.com>: > Il 02/07/2013 12:56, Peter Lieven ha scritto: >> >> Am 02.07.2013 um 12:49 schrieb Paolo Bonzini <pbonz...@redhat.com>: >> >>> Il 02/07/2013 12:36, Peter Lieven ha scritto: >>>>>>> Perhaps we can have a new "discard_zeroes" field in bdrv_get_info, and >>>>>>> the unmap functionality can be moved up to qemu-img convert? >>>>>> >>>>>> Is there any other storage protocol out there that could benefit from it? >>>>> >>>>> Definitely LVM. Perhaps in the future gluster too, though right now it >>>>> only supports discard on files, not block devices. >>>> >>>> Is discards on LVM sth that is already implemented in qemu? >>> >>> Yes, it supports BLKDISCARD (see handle_aiocb_discard in >>> block/raw-posix.c). Of course there is no way to query the host >>> discard_zeroes setting yet. >> >> No way in qemu or no way at all? > > No way in QEMU. Linux has the BLKDISCARDZEROES ioctl, it takes an int* > as the third argument and puts 0/1 in it.
okay, thanks for the pointer. if you all don't mind I would split up my series and first send a v3 which adds the unproblematic stuff and leave iscsi: let bdrv_create conditionally zero out the device block-migration: efficiently encode zero blocks out. both seem to need more time and cycles to follow the better approaches. Peter
