From c1eb2494559fb0f6ee2beecaedb2a415ff096056 Mon Sep 17 00:00:00 2001
From: Bob Gilligan <gilligan@vyatta.com>
Date: Thu, 3 Feb 2011 00:06:08 -0800
Subject: Bugfix 6773: Spread load of single-queue NICs across all CPUs.

The initial CPU selection function needs to take hyperthreading
into account.
---
 scripts/system/irq-affinity.pl | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'scripts')

diff --git a/scripts/system/irq-affinity.pl b/scripts/system/irq-affinity.pl
index fec90dc3..cf68c0d1 100755
--- a/scripts/system/irq-affinity.pl
+++ b/scripts/system/irq-affinity.pl
@@ -157,7 +157,11 @@ sub first_cpu {
 	unless defined($ifunit);
 
     my $threads = threads_per_core();
-    return ( $ifunit * $threads ) % $cpus;
+    # 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
-- 
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