"Michael S. Tsirkin" [off-list ref] writes:

On Tue, Feb 19, 2013 at 06:26:20PM +1030, Rusty Russell wrote:

quoted

virtio_scsi can really use this, to avoid the current hack of copying
the whole sg array.  Some other things get slightly neater, too.

Signed-off-by: Rusty Russell <redacted>

Hmm, this makes add_buf a bit slower. virtio_test results
(I'll send a patch to update the test shortly):

Before:
0.09user 0.01system 0:00.12elapsed 91%CPU (0avgtext+0avgdata 480maxresident)k
0inputs+0outputs (0major+145minor)pagefaults 0swaps

After:
0.11user 0.01system 0:00.13elapsed 90%CPU (0avgtext+0avgdata 480maxresident)k
0inputs+0outputs (0major+145minor)pagefaults 0swaps

Interesting: how much of this is due to the shim in virtqueue_add_buf()
to clean up the sg arrays?

(Perhaps we should make virtio_test run for longer, too).

BTW, you might be interested in:
        https://github.com/rustyrussell/stats.git

Which provides a useful filter for multiple results.

Cheers,
Rusty.