netdev - Re: tainted warnings with tcp splicing in 3.7.1

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Date:	Thu, 10 Jan 2013 10:42:08 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Rick Jones <rick.jones2@...com>
Cc:	Willy Tarreau <w@....eu>,
	Christian Becker <c.becker@...viangames.com>,
	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: tainted warnings with tcp splicing in 3.7.1

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@...dy:~/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  



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