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authorJohn Crispin <john@phrozen.org>2018-08-13 16:24:17 +0200
committerJohn Crispin <john@phrozen.org>2018-08-28 11:30:26 +0200
commit7af1fb9faafbc842fc727c49108f5fc4edc08601 (patch)
treea9c25ca32646fbe346c37814875980bc9c093ead
parent8e9a59a6b924469c0061d4bd945ae0c6dbfdecfe (diff)
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kernel: add a RPS balancer
By default the RPS delegation will happen by masking the last few bits of skb->hash. This patch adds an inermediate hash bucket that maps the masked hash to a RPS core. This makes RPS results much more deterministic on SMP systems. Signed-off-by: John Crispin <john@phrozen.org>
-rw-r--r--target/linux/generic/hack-4.14/600-net-core-add-RPS-balancer.patch93
1 files changed, 93 insertions, 0 deletions
diff --git a/target/linux/generic/hack-4.14/600-net-core-add-RPS-balancer.patch b/target/linux/generic/hack-4.14/600-net-core-add-RPS-balancer.patch
new file mode 100644
index 0000000000..6fc52ee25c
--- /dev/null
+++ b/target/linux/generic/hack-4.14/600-net-core-add-RPS-balancer.patch
@@ -0,0 +1,93 @@
+From 3e969c9695b45e1a052d43b367096ec99f2f0aac Mon Sep 17 00:00:00 2001
+From: John Crispin <john@phrozen.org>
+Date: Thu, 10 Aug 2017 15:58:29 +0200
+Subject: [PATCH] net: core: add RPS balancer
+
+This patch adds a hash bucket based rps hash balancer.
+
+Signed-off-by: John Crispin <john@phrozen.org>
+---
+ net/core/dev.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
+ 1 file changed, 56 insertions(+), 1 deletion(-)
+
+--- a/net/core/dev.c
++++ b/net/core/dev.c
+@@ -3626,6 +3626,58 @@ set_rps_cpu(struct net_device *dev, stru
+ return rflow;
+ }
+
++#define RPS_TBL_SIZE_SHIFT 10
++#define RPS_TBL_SIZE (1 << RPS_TBL_SIZE_SHIFT)
++struct rps_table {
++ int core;
++ struct timer_list expire;
++};
++static struct rps_table rps_table[RPS_TBL_SIZE];
++static int rps_table_last_core;
++
++static void rps_table_expire(unsigned long data)
++{
++ struct rps_table *entry = (struct rps_table *) data;
++
++ entry->core = -1;
++}
++
++static int rps_table_core(struct rps_map *map)
++{
++ int i;
++
++ for (i = 0; i < map->len; i++) {
++ int cpu = map->cpus[(rps_table_last_core + i + 1) % map->len];
++ if (cpu_online(cpu)) {
++ rps_table_last_core = cpu;
++ return cpu;
++ }
++ }
++ return map->cpus[0];
++}
++
++static int rps_table_lookup(struct rps_map *map, u32 hash)
++{
++ int bucket = hash & 0x3ff;
++
++ if (rps_table[bucket].core < 0)
++ rps_table[bucket].core = rps_table_core(map);
++ mod_timer(&rps_table[bucket].expire, jiffies + HZ);
++
++ return rps_table[bucket].core;
++}
++
++static void rps_table_init(void)
++{
++ int i;
++
++ for (i = 0; i < RPS_TBL_SIZE; i++) {
++ rps_table[i].core = -1;
++ setup_timer(&rps_table[i].expire, rps_table_expire,
++ (unsigned long) &rps_table[i]);
++ }
++}
++
+ /*
+ * get_rps_cpu is called from netif_receive_skb and returns the target
+ * CPU from the RPS map of the receiving queue for a given skb.
+@@ -3715,7 +3767,7 @@ static int get_rps_cpu(struct net_device
+ try_rps:
+
+ if (map) {
+- tcpu = map->cpus[reciprocal_scale(hash, map->len)];
++ tcpu = rps_table_lookup(map, hash);
+ if (cpu_online(tcpu)) {
+ cpu = tcpu;
+ goto done;
+@@ -8800,6 +8852,10 @@ static int __init net_dev_init(void)
+ sd->backlog.weight = weight_p;
+ }
+
++#ifdef CONFIG_RPS
++ rps_table_init();
++#endif
++
+ dev_boot_phase = 0;
+
+ /* The loopback device is special if any other network devices