netdev - Re: [PATCH v7] rps: Receive Packet Steering

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Date:	Thu, 18 Mar 2010 07:20:32 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Changli Gao <xiaosuo@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v7] rps: Receive Packet Steering

Le mercredi 17 mars 2010 à 16:50 -0700, Tom Herbert a écrit :
> >>
> >> # echo "0 1 0 1 0 1 1 1 1 1" >/sys/class/net/eth0/queues/rx-0/rps_map
> >> # cat /sys/class/net/eth0/queues/rx-0/rps_cpus
> >> 3
> >> # cat /sys/class/net/eth0/queues/rx-0/rps_map
> >> 0 1 0 1 0 1 1 1 1 1
> >> # echo 3 >/sys/class/net/eth0/queues/rx-0/rps_cpus
> >> # cat /sys/class/net/eth0/queues/rx-0/rps_map
> >> 0 1
> > 
> > Alternatively, the rps_map could be specified explicitly, which will
> > allow weighting.  For example "0 0 0 0 2 10 10 10"  would select CPUs
> > 0, 2, 10 for the map with weights four, one, and three respectively.
> > This would go back to have sysfs files with multiple values in them,
> > so it might not be the right interface.
> 
> Here is a patch for this...
> 
> Allow specification of CPUs in rps to be done with a vector instead of a bit map.  This allows relative weighting of CPUs in the map by repeating ones to give higher weight.
> 
> For example "echo 0 0 0 3 4 4 4 4 > /sys/class/net/eth0/queues/rx-0/rps_cpus"
> 
> assigns CPUs 0, 3, and 4 to the RPS mask with relative weights 3, 1, and 4 respectively.
> 

Hmm...

I believe we should keep existing sysfs cpumask interface, because its
the only workable thing on a PAGE_SIZE=4096 machine with 4096 cpus.

strlen("0 1 2 3 4 ... 4095") = 19369

Using base 16 instead of base 10 -> 16111



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