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authorEric Dumazet <eric.dumazet@gmail.com>2010-07-23 16:15:14 +0200
committerPatrick McHardy <kaber@trash.net>2010-07-23 16:15:14 +0200
commit2d59208943a3a2a6e0e30b6c84bb8ae80d444cd3 (patch)
tree37672b09c51845f5255185767f0624bf9c09d559 /extensions/libxt_cpu.man
parent59ccf53b9414d998afd6169cb2d6ba0f3c249081 (diff)
extension: add xt_cpu match
Kernel 2.6.36 supports xt_cpu match In some situations a CPU match permits a better spreading of connections, or select targets only for a given cpu. With Remote Packet Steering or multiqueue NIC and appropriate IRQ affinities, we can distribute trafic on available cpus, per session. (all RX packets for a given flow are handled by a given cpu) Some legacy applications being not SMP friendly, one way to scale a server is to run multiple copies of them. Instead of randomly choosing an instance, we can use the cpu number as a key so that softirq handler for a whole instance is running on a single cpu, maximizing cache effects in TCP/UDP stacks. Using NAT for example, a four ways machine might run four copies of server application, using a separate listening port for each instance, but still presenting an unique external port : iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 0 \ -j REDIRECT --to-port 8080 iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 1 \ -j REDIRECT --to-port 8081 iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 2 \ -j REDIRECT --to-port 8082 iptables -t nat -A PREROUTING -p tcp --dport 80 -m cpu --cpu 3 \ -j REDIRECT --to-port 8083 Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Patrick McHardy <kaber@trash.net>
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diff --git a/extensions/libxt_cpu.man b/extensions/libxt_cpu.man
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+.TP
+[\fB!\fP] \fB\-\-cpu\fP \fInumber\fP
+
+Match cpu handling this packet. cpus are numbered from 0 to NR_CPUS-1
+Can be used in combination with RPS (Remote Packet Steering) or
+multiqueue NICS to spread network traffic on different queues.
+.PP
+Example:
+.PP
+iptables \-t nat \-A PREROUTING \-p tcp \-\-dport 80 \-m cpu \-\-cpu 0
+ \-j REDIRECT \-\-to\-port 8080
+.PP
+iptables \-t nat \-A PREROUTING \-p tcp \-\-dport 80 \-m cpu \-\-cpu 1
+ \-j REDIRECT \-\-to\-port 8081
+.PP
+Available since linux 2.6.36