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#!/usr/bin/perl
# **** License ****
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# This code was originally developed by Vyatta, Inc.
# Portions created by Vyatta are Copyright (C) 2009,2010 Vyatta, Inc.
# All Rights Reserved.
#
# **** End License ****
#
use warnings;
use strict;
use Sys::Syslog qw(:standard :macros);
die "Usage: $0 ifname {auto | mask}\n" if ($#ARGV < 1);
my ($ifname, $mask) = @ARGV;
die "Error: Interface $ifname does not exist\n"
unless -d "/sys/class/net/$ifname";
openlog("irq-affinity","",LOG_LOCAL0);
my ( $cpus, $cores ) = cpuinfo();
if ($mask eq 'auto') {
affinity_auto($ifname);
} else {
affinity_mask($ifname, $mask);
}
exit 0;
# Get current irq assignments by reading /proc/interrupts
# returns reference to hash of interrupt infromation for given interface
# i.e. {'eth1'} => 22, {'eth1-tx-1'} => 31, ...
sub irqinfo {
my $ifname = shift;
my $irqmap;
open( my $f, '<', "/proc/interrupts" )
or die "Can't read /proc/interrupts";
while (<$f>) {
chomp;
my @cols = split;
# First column is IRQ number (and colon)
next unless /^\s*(\d+):\s/;
my $irq = $1;
# Skip columns for IRQ's per CPU
foreach my $name ( @cols[ $cpus+1 .. $#cols ] ) {
$name =~ s/,$//;
next unless ($name eq $ifname || $name =~ /^$ifname-/ );
$irqmap->{$name} = $irq;
}
}
close $f;
return $irqmap;
}
# Determine number of cpus and cores
sub cpuinfo {
my ( $cpu, $core );
open( my $f, '<', "/proc/cpuinfo" )
or die "Can't read /proc/cpuinfo";
while (<$f>) {
chomp;
if (/^cpu cores\s+:\s(\d+)$/) {
$core = $1;
}
elsif (/^processor\s+:\s+(\d)$/) {
$cpu = $1;
}
}
close $f;
return ( $cpu + 1, $core );
}
# Determine hyperthreading factor
# most CPU's have either 1 or 2 threads per core
sub threads_per_core {
return 1 unless defined($cores);
return $cpus / $cores;
}
# Set affinity value for a irq
sub set_affinity {
my ( $ifname, $irq, $mask ) = @_;
my $smp_affinity = "/proc/irq/$irq/smp_affinity";
syslog(LOG_INFO, "%s: irq %d affinity set to 0x%x", $ifname, $irq, $mask);
open( my $f, '>', $smp_affinity )
or die "Can't open: $smp_affinity : $!\n";
printf {$f} "%x\n", $mask;
close $f;
}
# set Receive Packet Steering mask
sub set_rps {
my ( $ifname, $q, $mask ) = @_;
# ignore if older kernel without RPS
my $rxq = "/sys/class/net/$ifname/queues";
return unless ( -d $rxq );
syslog(LOG_INFO, "%s: receive queue %d cpus set to 0x%x",
$ifname, $q, $mask);
my $rps_cpus = "$rxq/rx-$q/rps_cpus";
open( my $f, '>', $rps_cpus )
or die "Can't open: $rps_cpus : $!\n";
printf {$f} "%x\n", $mask;
close $f;
}
# For multi-queue NIC choose next cpu to be on next core
# FIXME assumes all cpu's online
sub next_cpu {
my $cpu = shift;
my $threads = threads_per_core();
$cpu += $threads;
if ( $cpu >= $cpus ) {
# wraparound to next thread on core 0
$cpu = ($cpu + 1) % $threads;
}
return $cpu;
}
# First cpu to assign for the queues
sub first_cpu {
my ($ifname, $numq) = @_;
# For multi-queue nic's always starts with 0
# This is less than ideal when there are more core's available
# than number of queues (probably should barber pole);
# but the Intel IXGBE needs CPU 0 <-> queue 0 because of flow director
return 0 if ($numq > 1);
# For single-queue nic choose IRQ based on name
# Ideally should make decision on least loaded CPU
my ($ifunit) = ($ifname =~ m/^[a-z]*(\d+)$/);
die "can't find number for $ifname\n"
unless defined($ifunit);
my $threads = threads_per_core();
# Give the load first to one CPU of each hyperthreaded core, then
# if there are enough NICs, give the load to the other CPU of
# each core.
my $ht_wrap = (($ifunit * $threads) / $cpus) % $threads;
return ((($ifunit * $threads) + $ht_wrap) % $cpus);
}
# Assignment for multi-queue NICs
# Assign each queue to successive cores
sub assign_multiqueue {
my ( $ifname, $numq, $irqmap, $irqfmt ) = @_;
my $cpu = first_cpu($ifname, $numq);
for ( my $q = 0 ; $q < $numq ; $q++ ) {
# handles multiple irq's per interface (tx/rx)
foreach my $fmt (@$irqfmt) {
my $name = sprintf( $fmt, $ifname, $q );
my $irq = $irqmap->{$name};
syslog(LOG_INFO, "%s: queue %d assign %s to cpu %d",
$ifname, $q, $name, $cpu );
# Assign CPU affinity for both IRQs
set_affinity( $ifname, $irq, 1 << $cpu );
# TODO use RPS to steer data if cores > queues?
}
$cpu = next_cpu($cpu);
}
}
# Affinity assignment function for single-queue NICs. The strategy
# here is to just spread the interrupts of different NICs evenly
# across all CPUs. That is the best we can do without monitoring the
# load and traffic patterns. So we just directly map the NIC unit
# number into a CPU number.
sub assign_single {
my ( $ifname, $irq ) = @_;
my $cpu = first_cpu($ifname, 1);
syslog( LOG_INFO, "%s: assign irq %d to cpu %d", $ifname, $irq, $cpu );
set_affinity( $ifname, $irq, 1 << $cpu );
my $threads = threads_per_core();
if ($threads > 1) {
# Use both threads on this cpu if hyperthreading
my $mask = ((1 << $threads) - 1) << $cpu;
set_rps($ifname, 0, $mask);
}
# MAYBE - Use all cpu's if no HT
}
# Mask must contain at least one CPU and
# no bits outside of range of available CPU's
sub check_mask {
my ($ifname, $name, $mask) = @_;
my $m = hex($mask);
die "$ifname: $name mask $mask has no bits set\n"
if ($m == 0);
die "$ifname: $name mask $mask too large for number of CPU's: $cpus\n"
if ($m >= 1 << $cpus);
}
# Set affinity (and RPS) based on mask
sub affinity_mask {
my ($ifname, $mask) = @_;
# match on <hex> or <hex>,<hex>
unless ($mask =~ /^([0-9a-f]+)(|,([0-9a-f]+))$/) {
die "$ifname: irq mask $mask is not a valid affinity mask\n"
}
my $irqmsk = $1;
my $rpsmsk = $3;
check_mask($ifname, "irq", $irqmsk);
check_mask($ifname, "rps", $rpsmsk) if $rpsmsk;
my $irqmap = irqinfo($ifname);
while (my ($name, $irq) = each (%{$irqmap})) {
syslog( LOG_INFO, "%s: assign irq %d mask %s", $name, $irq, $irqmsk);
set_affinity($name, $irq, hex($irqmsk));
}
set_rps($ifname, 0, hex($rpsmsk)) if $rpsmsk;
}
# The auto strategy involves trying to achieve the following goals:
#
# - Spread the receive load among as many CPUs as possible.
#
# - For all multi-queue NICs in the system that provide both tx and
# rx queues, keep all of the queues that share the same queue
# number on same CPUs. I.e. tx and rx queue 0 of all such NICs
# should interrupt one CPU; tx and rx queue 1 should interrupt a
# different CPU, etc.
#
# - If hyperthreading is supported and enabled, avoid assigning
# queues to both CPUs of a hyperthreaded pair if there are enough
# CPUs available to do that.
sub affinity_auto {
my $ifname = shift;
my $irqmap = irqinfo($ifname);
my @irqnames = keys %{$irqmap};
my $numirq = scalar(@irqnames);
# Figure out what style of irq naming is being used
if ( $numirq == 1 ) {
my $irq = $irqmap->{$ifname};
assign_single( $ifname, $irq) if $irq;
} elsif ($numirq > 1) {
# Match seperate irq for Rx and Tx
my $nrx = grep { /^$ifname-rx-/ } @irqnames;
if ( $nrx > 0 ) {
my $ntx = grep { /^$ifname-tx-/ } @irqnames;
die "$ifname: rx queues $nrx != tx queues $ntx"
unless ( $nrx == $ntx );
return assign_multiqueue( $ifname, $nrx, $irqmap,
[ '%s-rx-%d', '%s-tx-%d' ] );
}
# Match eth0-N form
my $nq = grep { /^$ifname-\d+$/ } @irqnames;
if ( $nq > 0 ) {
return assign_multiqueue( $ifname, $nq, $irqmap, [ '%s-%d' ] );
}
# Match eth-sometext-N
if ($irqnames[0] =~ /^$ifname(.*-)\d+$/) {
my $sep = $1;
my $regex = '^' . $ifname . $sep . '\d+$';
$nq = grep { $regex } @irqnames;
if ( $nq > 0 ) {
return assign_multiqueue( $ifname, $nq, $irqmap,
[ "%s$sep%d" ] );
}
}
syslog(LOG_ERR, "%s: Unknown multiqueue irq naming: %s\n", $ifname,
join(' ', @irqnames));
}
}
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