On Tue, Apr 14, 2015 at 7:49 AM, Peter Lieven <p...@kamp.de> wrote: > Ronnie came up with an idea to reduce latency if !bs->enable_write_cache for > an iSCSI device. > > If !bs->enable_write_cache Qemu sends a flush after every single write. What > could be done is > the following: > > if (!bs->enable_write_cache) > set FUA (force unit access) and DPO (disable page out) bits in every write > cmd > make iscsi_co_flush a NOOP in this case. > > Your thoughts?
Do other commands besides writes rely on iscsi_co_flush()? Paolo: I checked NBD and noticed there is an inconsistency there. nbd_co_writev_1() uses FUA when bs->enable_write_cache == true but it also sends flushes. Does that mean it's doing unnecessary work? Stefan
