Re: [PATCH 0/3] [RFC] vhost: micro vhost optimization

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Tue, May 10, 2016 at 02:49:43PM -0700, Rich Lane wrote:
> I see a significant performance improvement with these patches, around 5% at 64
> bytes.

Thanks for testing.

> 
> The one patch that didn't give any performance boost for me was "vhost: arrange
> virtio_net fields for better cache sharing".

Yeah, same here from my test. I mean, in theory, it should give us a
tiny boost, it doesn't in real life though. And since it (should) do
no harm, I would still include this patch in this set. Maybe I should
have noted at first that no real perf gain from the 3rd patch.

	--yliu

> 
> Tested-by: Rich Lane <rich.lane@bigswitch.com>
> 
> On Mon, May 2, 2016 at 5:46 PM, Yuanhan Liu <yuanhan.liu@linux.intel.com>
> wrote:
> 
>     Here is a small patch set does the micro optimization, which brings about
>     10% performance boost in my 64B packet testing, with the following topo:
> 
>         pkt generator <----> NIC <-----> Virtio NIC
> 
>     Patch 1 pre updates the used ring and update them in batch. It should be
>     feasible from my understanding: there will be no issue, guest driver will
>     not start processing them as far as we haven't updated the "used->idx"
>     yet. I could miss something though.
> 
>     Patch 2 saves one check for small packets (that can be hold in one desc
>     buf and mbuf).
> 
>     Patch 3 moves several frequently used fields into one cache line, for
>     better cache sharing.
> 
>     Note that this patch set is based on my latest vhost ABI refactoring
>     patchset.
> 
> 
>     ---
>     Yuanhan Liu (3):
>       vhost: pre update used ring for Tx and Rx
>       vhost: optimize dequeue for small packets
>       vhost: arrange virtio_net fields for better cache sharing
> 
>      lib/librte_vhost/vhost-net.h  |   8 +--
>      lib/librte_vhost/vhost_rxtx.c | 110
>     ++++++++++++++++++++++++------------------
>      2 files changed, 68 insertions(+), 50 deletions(-)
>    
>     --
>     1.9.0
> 
> 
>