Am 17.07.2013 um 19:04 schrieb Paolo Bonzini <pbonz...@redhat.com>: > Il 17/07/2013 19:02, Peter Lieven ha scritto: >> For Disks we always use read/write16 so i think we Should also use >> writesame16. Or not? > > Yes. > > Remember you can still use UNMAP if LBPRZ=0.
I can always use it if writesame is not available, but in this case bdi->discard_zeroes must be 0. Maybe we should call it discard_writes_zeroes or similar. Discard_zeroes is sth that should only indicate if lbprz == 1. At least if we refer to the Linux ioctl. We could include both in BDI. Peter > > Paolo > >> Von meinem iPhone gesendet >> >> Am 17.07.2013 um 18:31 schrieb ronnie sahlberg <ronniesahlb...@gmail.com>: >> >>> On Wed, Jul 17, 2013 at 9:27 AM, Paolo Bonzini <pbonz...@redhat.com> wrote: >>>> Il 17/07/2013 17:54, ronnie sahlberg ha scritto: >>>>> I think it is reasonable to assume that IF LBPRZ==1 and IF it is an >>>>> "optimal unmap request" then the blocks will become unmapped and they >>>>> will read back as 0. >>>> >>>> Yes, but it is not reasonable to assume that bdrv_discard will only >>>> receive "optimal" requests. Thus, using WRITE SAME for LBPRZ=1, and not >>>> exposing LBPRZ=1 if LBPWS=0 (may also use LBPWS10 depending on the >>>> capacity), is the safer thing to do. >>>> >>>> Paolo >>> >>> ACK. >>> >>> WRITESAME10/16 with UNMAP flag set is probably best. >
