net: sched: Allow changing default qdisc to FQ-PIE

Similar to fq_codel and the other qdiscs that can set as default,
fq_pie is also suitable for general use without explicit configuration,
which makes it a valid choice for this.

This is useful in situations where a painless out-of-the-box solution
for reducing bufferbloat is desired but fq_codel is not necessarily the
best choice. For example, fq_pie can be better for DASH streaming, but
there could be more cases where it's the better choice of the two simple
AQMs available in the kernel.
Signed-off-by: Danny Lin <danny@kdrag0n.dev>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/Kconfig

@@ -468,6 +468,9 @@ choice
 	config DEFAULT_FQ_CODEL
 		bool "Fair Queue Controlled Delay" if NET_SCH_FQ_CODEL
 
+	config DEFAULT_FQ_PIE
+		bool "Flow Queue Proportional Integral controller Enhanced" if NET_SCH_FQ_PIE
+
 	config DEFAULT_SFQ
 		bool "Stochastic Fair Queue" if NET_SCH_SFQ
 
@@ -480,6 +483,7 @@ config DEFAULT_NET_SCH
 	default "pfifo_fast" if DEFAULT_PFIFO_FAST
 	default "fq" if DEFAULT_FQ
 	default "fq_codel" if DEFAULT_FQ_CODEL
+	default "fq_pie" if DEFAULT_FQ_PIE
 	default "sfq" if DEFAULT_SFQ
 	default "pfifo_fast"
 endif