irq-affinity: add workaround to avoid some cpu's

For routing and other applications it is helpful to provide some
mechanism to reserve some set of CPU's and not assign interface
IRQ's to them.

Uses environment variable VYATTA_IRQAFFINITY_BANNED_CPUS
as mechanism similar to irqbalance(8).

1 files changed, 26 insertions, 8 deletions

diff --git a/scripts/system/irq-affinity.pl b/scripts/system/irq-affinity.pl
index 2f023b7a..409eb8f6 100755
--- a/scripts/system/irq-affinity.pl
+++ b/scripts/system/irq-affinity.pl
@@ -131,17 +131,31 @@ sub set_rps {
     close $f;
 }
 
+# Check if the current if this cpu is in the banned mask
+# Uses environment variable VYATTA_IRQAFFINITY_BANNED_CPUS
+#  to mask cpus which irq affinity script should ignore
+sub skip_cpu {
+    my $cpu = shift;
+    my $banned = $ENV{'VYATTA_IRQAFFINITY_BANNED_CPUS'};
+
+    return unless defined($banned);	# false
+
+    return ((1 << $cpu) & hex($banned)) != 0;
+}
+
 # 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 $origcpu = shift;
     my $threads = threads_per_core();
+    my $cpu = $origcpu;
 
-    $cpu += $threads;
-    if ( $cpu >= $cpus ) {
-	# wraparound to next thread on core 0
-	$cpu = ($cpu + 1) % $threads;
-    }
+    do {
+	$cpu += $threads;
+	if ( $cpu >= $cpus ) {
+	    # wraparound to next thread on core 0
+	    $cpu = ($cpu + 1) % $threads;
+	}
+    } while ($cpu != $origcpu && skip_cpu($cpu));
 
     return $cpu;
 }
@@ -157,11 +171,15 @@ sub choose_cpu {
 	unless defined($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);
+    my $cpu = ((($ifunit * $threads) + $ht_wrap) % $cpus);
+
+    $cpu = next_cpu($cpu) if skip_cpu($cpu);
+    return $cpu;
 }
 
 # Assignment for multi-queue NICs