Hello,

On 08/17/2010 03:23 PM, Christoph Hellwig wrote:

quoted

Hmmm... the underlying storage could be md/dm RAIDs in which case FUA
should be cheaper than FLUSH.

If someone ever wrote a virtio-blk backend that sits directly ontop
of the Linux block layer that would be true.  Of the five known
virtio-blk backends all operate on normal files using the Posix I/O
APIs, or the Linux aio API (optionally in qemu) or in-kernel
vfs_read/vfs_write (vhost-blk).

Right.

Given how little testing lguest gets compared to qemu I really don't
want a protocol addition for it unless it really buys us something.
Once we're done with this barrier conversion I plan into benchmarking
FUA and a pre-flush tag on the command for virtio in real life setups,
and see if it actually buys us anything.

Hmmm... yeah, we can drop it.  Michael, what do you think?

Thanks.

-- 
tejun