Re: tainted warnings with tcp splicing in 3.7.1

Eric Dumazet
2013-01-10T18:42:21Z

On Thu, 2013-01-10 at 10:22 -0800, Rick Jones wrote:
> On 01/10/2013 08:20 AM, Eric Dumazet wrote:
> > I also want to thanks Rick, as the latest netperf has splice() support.
> >
> > Thanks Rick !
>
> You are quite welcome - and thank you for helping me get it to actually
> work :)
>
> Those wishing to try it themselves should grab the top-of-trunk netperf
> bits from http://www.netperf.org/svn/netperf2/trunk . The use of
> splice() is gated by a test-specific -V option:
>
> raj@tardy:~/netperf2_trunk/src$ ./netperf -t omni -- -d recv -V
> OMNI Receive TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to
> localhost.localdomain () port 0 AF_INET : copy avoidance : demo
> Remote Local Remote Elapsed Throughput Throughput
> Send Socket Recv Socket Send Time Units
> Size Size Size (sec)
> Final Final
> 1661688 4194304 16384 10.00 26103.14 10^6bits/s
>
> You should see that "copy avoidance" appearing in the test banner. It
> will also "take" for things like a migrated TCP_mumble test. For those
> cases where you don't see a throughput change, enabling CPU utilization
> measurement and looking at that and service demand should show a difference.

Thanks Rick !

Can we use zero copy for the sender as well (sendfile() or vmsplice()) ?

Here are some results :

Reference time (no splice())

# ./netperf -H 127.0.0.1 -t omni -- -d recv
OMNI Receive TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 127.0.0.1 ()
port 0 AF_INET
catcher: timer popped with times_up != 0
Remote Local Remote Elapsed Throughput Throughput
Send Socket Recv Socket Send Time Units
Size Size Size (sec)
Final Final
2097152 2097152 16384 10.00 33237.74 10^6bits/s

zero copy at receiver (splice(socket ->pipe), splice(pipe -> /dev/null))

# ./netperf -H 127.0.0.1 -t omni -- -d recv -V
OMNI Receive TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 127.0.0.1 ()
port 0 AF_INET : copy avoidance
catcher: timer popped with times_up != 0
Remote Local Remote Elapsed Throughput Throughput
Send Socket Recv Socket Send Time Units
Size Size Size (sec)
Final Final
1325580 2097152 16384 10.00 51980.60 10^6bits/s