Bugfix 2593: Introduce automatic static IRQ affinity balancing for some NICs.

This change implements a mechanism for setting the IRQ affinity of NIC
interrupts in a way that is optimally balanced.  The affinity settings
are static, and are set up at configuration time.  I've added "auto"
as a new legal value to the "interfaces ethernet ethX smp_affinity"
configuration parameter.  If this value is set, then the system
attempts to perform automatic IRQ affinity assignment.

At this time, automatic IRQ affinity is supported only for multiqueue
NICs that use the igb or bnx2 drivers.  Even with these two,
differences in the organization of queues and their naming convention
necessitate some NIC-specific code.  The assignment strategy attempts
to assign all queues of all NICs that share the same queue number to
the same CPU.  This has been shown to be optimal for IP forwarding
workloads in 2.6.31 kernels.

Setting the value to "auto" for NICs that use other drivers will be a
no-op.

1 files changed, 283 insertions, 0 deletions

diff --git a/scripts/vyatta-auto-irqaffin.pl b/scripts/vyatta-auto-irqaffin.pl
new file mode 100644
index 0000000..521a181
--- /dev/null
+++ b/scripts/vyatta-auto-irqaffin.pl
@@ -0,0 +1,283 @@
+#!/usr/bin/perl
+#
+# Module: vyatta-auto-irqaffin.pl
+#
+# **** 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 Vyatta, Inc.
+# All Rights Reserved.
+#
+# Author: Bob Gilligan (gilligan@vyatta.com)
+# Date: October 2009
+# Description: Script to configure optimal IRQ affinity for NICs.
+#
+# **** End License ****
+#
+
+# This script attempts to perform a static affinity assignment for network
+# interfaces.  It is primarily targeted at supporting multi-queue NICs. 
+# Since different NICs may have different queue organizations, and
+# because there is no standard API for learning the mapping between
+# queues and IRQ numbers, different code is required for each driver.
+#
+# The general strategy includes:
+#  - Spread the receive load among as many CPUs as possible.
+#  - For NICs that provide both rx and tx queue, keep the tx queue
+#    on the same CPU as the corresponding rx queue.
+#  - For all multi-queue NICs in the system, the same tx and rx queue
+#    numbers should interrupt the same CPUs.  I.e. tx and rx queue 0
+#    of all NICs should interrupt the same CPU.
+#  - 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.
+#
+
+
+use lib "/opt/vyatta/share/perl5";
+use Getopt::Long;
+
+use warnings;
+use strict;
+
+# Send output of shell commands to syslog for debugging and so that
+# the user is not confused by it.  Log at debug level, which is supressed
+# by default, so that we don't unnecessarily fill up the syslog file.
+my $logger = 'logger -t firewall-cfg -p local0.debug --';
+
+# Enable printing debug output to stdout.
+my $debug_flag = 0;
+my $syslog_flag = 0;
+
+my $setup_ifname;
+
+GetOptions("setup=s"		=> \$setup_ifname,
+	   "debug"		=> \$debug_flag
+    );
+
+sub log_msg {
+    my $message = shift;
+
+    print "DEBUG: $message" if $debug_flag;
+    system("$logger DEBUG: \"$message\"") if $syslog_flag;
+}
+
+
+# Affinity strategy function for the igb driver.  NICs using this
+# driver have an equal number of rx and tx queues.  The first part of
+# the strategy for optimal performance is to assign irq of each queue
+# in a pair of tx and rx queues that have the same queue number to the
+# same CPU.  I.e., assign queue 0 to CPU X, queue 1 to CPU Y, etc.
+# The second part is to avoid assigning any queues to the second CPU
+# in a hyper-threaded pair, if posible.  I.e., if CPU 0 and 1 are
+# hyper-threaded pairs, then assign a queue to CPU 0, but try to avoid
+# assigning one to to CPU 1.  But if we have more queues than CPUs, then
+# it is OK to assign some to the second CPU in a hyperthreaded pair.
+# 
+sub igb_func{
+    my ($ifname, $numcpus, $numcores) = @_;
+    my $rx_queues;	# number of rx queues
+    my $tx_queues;	# number of tx queues
+    my $ht_factor;	# 2 if HT enabled, 1 if not
+
+    log_msg("igb_func was called.\n");
+
+    if ($numcpus > $numcores) {
+	$ht_factor = 2;
+    } else {
+	$ht_factor = 1;
+    }
+
+    log_msg("ht_factor is $ht_factor.\n");
+
+    # Figure out how many queues we have
+
+    $rx_queues=`grep "$ifname-rx-" /proc/interrupts | wc -l`;
+    $rx_queues =~ s/\n//;
+
+    $tx_queues=`grep "$ifname-tx-" /proc/interrupts | wc -l`;
+    $tx_queues =~ s/\n//;
+
+    log_msg("rx_queues is $rx_queues.  tx_queues is $tx_queues\n");
+    
+    if ($rx_queues != $tx_queues) {
+	printf("Error: rx and tx queues don't match for igb driver.\n");
+	exit 1;
+    }
+
+    # For i = 0 to number of queues:
+    #    Affinity of rx and tx queue $i gets CPU ($i * (2 if HT, 1 if no HT)) 
+    #                                   % number_of_cpus
+    for (my $queue = 0, my $cpu = 0; ($queue < $rx_queues) ; $queue++) {
+	# Generate the hex string for the bitmask representing this CPU
+	my $cpu_bit = 1 << $cpu;
+	my $cpu_hex = sprintf("%x", $cpu_bit);
+	log_msg ("queue=$queue cpu=$cpu cpu_bit=$cpu_bit cpu_hex=$cpu_hex\n");
+	
+	# Get the IRQ number for RX queue
+	my $rx_irq=`grep "$ifname-rx-$queue" /proc/interrupts | awk -F: '{print \$1}'`;
+	$rx_irq =~ s/\n//;
+	$rx_irq =~ s/ //g;
+
+	# Get the IRQ number for TX queue
+	my $tx_irq=`grep "$ifname-tx-$queue" /proc/interrupts | awk -F: '{print \$1}'`;
+	$tx_irq =~ s/\n//;
+	$tx_irq =~ s/ //g;
+
+	log_msg("rx_irq = $rx_irq.  tx_irq = $tx_irq\n");
+
+	# Assign CPU affinity for both IRQs
+	system "echo $cpu_hex > /proc/irq/$rx_irq/smp_affinity";
+	system "echo $cpu_hex > /proc/irq/$tx_irq/smp_affinity";
+
+	$cpu += $ht_factor;
+
+	if ($cpu >= $numcpus) {
+	    # Must "wrap"
+	    $cpu %= $numcpus;
+
+	    if ($ht_factor > 1) {
+		# Next time through, select the other CPU in a hyperthreaded 
+		# pair.
+		if ($cpu == 0) {
+		    $cpu++;
+		} else {
+		    $cpu--;
+		}
+	    }
+	}
+    }
+};
+
+# Similar strategy as for igb driver, but Broadcom NICs do not have
+# separate receive and transmit queues.
+sub bnx2_func{
+    my ($ifname, $numcpus, $numcores) = @_;
+    my $num_queues;	# number of queues
+    my $ht_factor;	# 2 if HT enabled, 1 if not
+
+    log_msg("bnx2_func was called.\n");
+
+    # Figure out how many queues we have
+    $num_queues=`grep "$ifname-" /proc/interrupts | wc -l`;
+    $num_queues =~ s/\n//;
+
+    log_msg("num_queues=$num_queues\n");
+
+    if ($num_queues <=0) {
+	printf("ERROR: No queues found for $ifname\n");
+	exit 1;
+    }
+
+    if ($numcpus > $numcores) {
+	$ht_factor = 2;
+    } else {
+	$ht_factor = 1;
+    }
+
+    log_msg("ht_factor is $ht_factor.\n");
+
+    for (my $queue = 0, my $cpu = 0; ($queue < $num_queues) ; $queue++) {
+	# Generate the hex string for the bitmask representing this CPU
+	my $cpu_bit = 1 << $cpu;
+	my $cpu_hex = sprintf("%x", $cpu_bit);
+	log_msg ("queue=$queue cpu=$cpu cpu_bit=$cpu_bit cpu_hex=$cpu_hex\n");
+	
+	# Get the IRQ number for the queue
+	my $irq=`grep "$ifname-$queue" /proc/interrupts | awk -F: '{print \$1}'`;
+	$irq =~ s/\n//;
+	$irq =~ s/ //g;
+
+	log_msg("irq = $irq.\n");
+
+	# Assign CPU affinity for this IRQs
+	system "echo $cpu_hex > /proc/irq/$irq/smp_affinity";
+
+	$cpu += $ht_factor;
+	if ($cpu >= $numcpus) {
+	    # Must "wrap"
+	    $cpu %= $numcpus;
+
+	    if ($ht_factor > 1) {
+		# Next time through, select the other CPU in a hyperthreaded
+		# pair.
+		if ($cpu == 0) {
+		    $cpu++;
+		} else {
+		    $cpu--;
+		}
+	    }
+	}
+    }
+}
+
+my %driver_hash = ( 'igb' => \&igb_func,
+		    'ixbg' => \&igb_func,
+		    'bnx2' =>\&bnx2_func );
+
+if (defined $setup_ifname) {
+    # Set up automatic IRQ affinity for the named interface
+
+    log_msg("setup $setup_ifname\n");
+
+    my $ifname = $setup_ifname;	# shorter variable name
+    my $drivername;	# Name of the NIC driver, e.g. "igb".
+    my $numcpus;	# Number of Linux "cpus"
+    my $numcores;	# Number of unique CPU cores
+    my $driver_func;	# Pointer to fuction specific to a driver
+
+    # Determine how many CPUs the machine has
+    $numcpus=`grep "^processor" /proc/cpuinfo | wc -l`;
+    $numcpus =~ s/\n//;
+
+    log_msg("numcpus is $numcpus\n");
+
+    if ($numcpus == 1) {
+	# Nothing to do if we only have one CPU, so just exit quietly.
+	exit 0;
+    }
+
+    # Verify that interface exists
+    if (! (-e "/proc/sys/net/ipv4/conf/$ifname")) {
+	printf("Error: Interface $ifname does not exist\n");
+	exit 1;
+    }
+
+    # Figure out what driver this NIC is using.
+    $drivername=`ethtool -i $ifname | grep "^driver" | awk '{print \$2}'`;
+    $drivername =~ s/\n//;
+
+    log_msg("drivername is $drivername\n");
+
+    $driver_func = $driver_hash{$drivername};
+
+    # We only support a couple of drivers at this time, so just exit
+    # if its not one we support.
+    if (! defined($driver_func)) {
+	printf("Automatic SMP affinity not supported for NICs using the $drivername driver.\n");
+	exit 0;	# not an error
+    }
+
+    # Determine whether machine has hyperthreading enabled
+    $numcores=`grep "^core id" /proc/cpuinfo | uniq | wc -l`;
+    $numcores =~ s/\n//;
+    
+    log_msg("numcores is $numcores.\n");
+
+    &$driver_func($ifname, $numcpus, $numcores);
+
+    exit 0;
+}
+
+printf("Must specify options.\n");
+exit(1);
+
+