netdev - Re: Re: Re: Re: Re: Re: limited network bandwidth with 3.2.x kernels

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Date:	Wed, 15 Feb 2012 07:06:56 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Neal Cardwell <ncardwell@...gle.com>
Cc:	alekcejk@...glemail.com, netdev@...r.kernel.org
Subject: Re: Re: Re: Re: Re: Re: limited network bandwidth with 3.2.x kernels

Le mercredi 15 février 2012 à 01:03 -0500, Neal Cardwell a écrit :
> There are some potentially interesting differences in sysctl values:
> 
> > diff -u /tmp/sysctl-a-3.1.txt /tmp/sysctl-a-3.2.txt  | grep mem_def
> -net.core.wmem_default = 114688
> -net.core.rmem_default = 114688
> +net.core.wmem_default = 163840
> +net.core.rmem_default = 163840
> 
> Can you please try running this as root on the 3.2 kernel and then see
> what sort of performance you get:
> 
> sysctl net.core.rmem_default=114688
> 
> This should make the 3.2 config closer to the 3.1 config. Should be
> interesting to see if the behavior is more similar when that happens.
> 
> neal

These changes are normal, since skb truesize  now include shared_info.

By the way, these params are not used for tcp streams.

This is why I asked netstat -s values, to check if we had drops because
of truesize limits.

Its not the case here since skb are not too fat (as some NICS can do,
using a full PAGE to hold a single 1500 bytes frams)



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