net: rps: send out pending IPI's on CPU hotplug
IPI's from the victim cpu are not handled in dev_cpu_callback.
So these pending IPI's would be sent to the remote cpu only when
NET_RX is scheduled on the victim cpu and since this trigger is
unpredictable it would result in packet latencies on the remote cpu.
This patch add support to send the pending ipi's of victim cpu.
Change-Id: I6e688bf0d09a952468eec18f80ce6b21bf370ef1
Signed-off-by: Ashwanth Goli <ashwanth@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index bc129b0..7db04c2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4843,6 +4843,19 @@
}
EXPORT_SYMBOL(__skb_gro_checksum_complete);
+static void net_rps_send_ipi(struct softnet_data *remsd)
+{
+#ifdef CONFIG_RPS
+ while (remsd) {
+ struct softnet_data *next = remsd->rps_ipi_next;
+
+ if (cpu_online(remsd->cpu))
+ smp_call_function_single_async(remsd->cpu, &remsd->csd);
+ remsd = next;
+ }
+#endif
+}
+
/*
* net_rps_action_and_irq_enable sends any pending IPI's for rps.
* Note: called with local irq disabled, but exits with local irq enabled.
@@ -4858,20 +4871,7 @@
local_irq_enable();
/* Send pending IPI's to kick RPS processing on remote cpus. */
- while (remsd) {
- struct softnet_data *next = remsd->rps_ipi_next;
-
- if (cpu_online(remsd->cpu)) {
- smp_call_function_single_async(remsd->cpu,
- &remsd->csd);
- } else {
- pr_err("%s() cpu offline\n", __func__);
- rps_lock(remsd);
- remsd->backlog.state = 0;
- rps_unlock(remsd);
- }
- remsd = next;
- }
+ net_rps_send_ipi(remsd);
} else
#endif
local_irq_enable();
@@ -8028,7 +8028,7 @@
struct sk_buff **list_skb;
struct sk_buff *skb;
unsigned int cpu, oldcpu = (unsigned long)ocpu;
- struct softnet_data *sd, *oldsd;
+ struct softnet_data *sd, *oldsd, *remsd;
if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
return NOTIFY_OK;
@@ -8072,6 +8072,13 @@
raise_softirq_irqoff(NET_TX_SOFTIRQ);
local_irq_enable();
+#ifdef CONFIG_RPS
+ remsd = oldsd->rps_ipi_list;
+ oldsd->rps_ipi_list = NULL;
+#endif
+ /* send out pending IPI's on offline CPU */
+ net_rps_send_ipi(remsd);
+
/* Process offline CPU's input_pkt_queue */
while ((skb = __skb_dequeue(&oldsd->process_queue))) {
netif_rx_ni(skb);