netdev - Re: [PATCH v6] net: batch skb dequeueing from softnet input_pkt

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Message-ID: <1272818131.2173.127.camel@edumazet-laptop>
Date:	Sun, 02 May 2010 18:35:31 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	David Miller <davem@...emloft.net>, hadi@...erus.ca,
	xiaosuo@...il.com, therbert@...gle.com, shemminger@...tta.com,
	netdev@...r.kernel.org, lenb@...nel.org, arjan@...radead.org
Subject: Re: [PATCH v6] net: batch skb dequeueing from softnet
 input_pkt_queue

Le dimanche 02 mai 2010 à 17:46 +0200, Andi Kleen a écrit :
> > In this test, all 16 queues of one BCM57711E NIC (1Gb link) delivers
> >  packets at about 1.300.000 pps to 16 cpus (one cpu per queue) and these
> > packets are then redistributed by RPS to same 16 cpus, generating about
> > 650.000 IPI per second.
> 
> BTW if rps was SMT aware it could avoid a lot of the IPIs in the first place.

RPS do what you want, just stick a good cpumask, not a unware one :)

In my test, I specifically do something 'stupid' like :

echo fffe >/sys/class/net/bond0.2240/queues/rx-0/rps_cpus
echo fffd >/sys/class/net/bond0.2240/queues/rx-1/rps_cpus
echo fffb >/sys/class/net/bond0.2240/queues/rx-2/rps_cpus
echo fff7 >/sys/class/net/bond0.2240/queues/rx-3/rps_cpus

echo ffef >/sys/class/net/bond0.2240/queues/rx-4/rps_cpus
echo ffdf >/sys/class/net/bond0.2240/queues/rx-5/rps_cpus
echo ffbf >/sys/class/net/bond0.2240/queues/rx-6/rps_cpus
echo ff7f >/sys/class/net/bond0.2240/queues/rx-7/rps_cpus

echo feff >/sys/class/net/bond0.2240/queues/rx-8/rps_cpus
echo fdff >/sys/class/net/bond0.2240/queues/rx-9/rps_cpus
echo fbff >/sys/class/net/bond0.2240/queues/rx-10/rps_cpus
echo f7ff >/sys/class/net/bond0.2240/queues/rx-11/rps_cpus

echo efff >/sys/class/net/bond0.2240/queues/rx-12/rps_cpus
echo dfff >/sys/class/net/bond0.2240/queues/rx-13/rps_cpus
echo bfff >/sys/class/net/bond0.2240/queues/rx-14/rps_cpus
echo 7fff >/sys/class/net/bond0.2240/queues/rx-15/rps_cpus

echo 0001 >/proc/irq/*/eth1-fp-0/../smp_affinity
echo 0002 >/proc/irq/*/eth1-fp-1/../smp_affinity
echo 0004 >/proc/irq/*/eth1-fp-2/../smp_affinity
echo 0008 >/proc/irq/*/eth1-fp-3/../smp_affinity
echo 0010 >/proc/irq/*/eth1-fp-4/../smp_affinity
echo 0020 >/proc/irq/*/eth1-fp-5/../smp_affinity
echo 0040 >/proc/irq/*/eth1-fp-6/../smp_affinity
echo 0080 >/proc/irq/*/eth1-fp-7/../smp_affinity
echo 0100 >/proc/irq/*/eth1-fp-8/../smp_affinity
echo 0200 >/proc/irq/*/eth1-fp-9/../smp_affinity
echo 0400 >/proc/irq/*/eth1-fp-10/../smp_affinity
echo 0800 >/proc/irq/*/eth1-fp-11/../smp_affinity
echo 1000 >/proc/irq/*/eth1-fp-12/../smp_affinity
echo 2000 >/proc/irq/*/eth1-fp-13/../smp_affinity
echo 4000 >/proc/irq/*/eth1-fp-14/../smp_affinity
echo 8000 >/proc/irq/*/eth1-fp-15/../smp_affinity


You mean we can wakeup a thread with something else than an IPI ?



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