kernel: add codel and fq_codel to generic 3.3 patch set (based on patch by Dave Täht)

Codel is a new AQM algorithm and RED replacement designed by
Kathie Nichols and Van Jacobson, and published in ACM queue:

http://queue.acm.org/detail.cfm?id=2209336

Codel stands for "Controlled Delay", and needs no knobs in the
general case, twiddled, for optimum results. It aims for 5ms of
delay, at most, when in use.

Additionally,

fq_codel (by eric dumazet) builds on codel to provide fair queuing
superior to what could be had with SFQ, and drop behavior saner
than RED, BLUE, or choke.

These patches are backported from net-next and are known to work
on Linux 3.3.4 and later.

Includes updates to codel for better portability and speed

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@31756 3c298f89-4303-0410-b956-a3cf2f4a3e73

1 files changed, 85 insertions, 0 deletions

diff --git a/target/linux/generic/patches-3.3/045-codel-use-u16-field-instead-of-31bits-for-rec_inv_sq.patch b/target/linux/generic/patches-3.3/045-codel-use-u16-field-instead-of-31bits-for-rec_inv_sq.patch
new file mode 100644
index 0000000000..814aebc61d
--- /dev/null
+++ b/target/linux/generic/patches-3.3/045-codel-use-u16-field-instead-of-31bits-for-rec_inv_sq.patch
@@ -0,0 +1,85 @@
+From 6ff272c9ad65eda219cd975b9da2dbc31cc812ee Mon Sep 17 00:00:00 2001
+From: Eric Dumazet <eric.dumazet@gmail.com>
+Date: Sat, 12 May 2012 21:23:23 +0000
+Subject: [PATCH 46/50] codel: use u16 field instead of 31bits for
+ rec_inv_sqrt
+
+David pointed out gcc might generate poor code with 31bit fields.
+
+Using u16 is more than enough and permits a better code output.
+
+Also make the code intent more readable using constants, fixed point arithmetic
+not being trivial for everybody.
+
+Suggested-by: David Miller <davem@davemloft.net>
+Signed-off-by: Eric Dumazet <edumazet@google.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ include/net/codel.h |   25 +++++++++++++++----------
+ 1 file changed, 15 insertions(+), 10 deletions(-)
+
+--- a/include/net/codel.h
++++ b/include/net/codel.h
+@@ -133,13 +133,17 @@ struct codel_params {
+ struct codel_vars {
+ 	u32		count;
+ 	u32		lastcount;
+-	bool		dropping:1;
+-	u32		rec_inv_sqrt:31;
++	bool		dropping;
++	u16		rec_inv_sqrt;
+ 	codel_time_t	first_above_time;
+ 	codel_time_t	drop_next;
+ 	codel_time_t	ldelay;
+ };
+ 
++#define REC_INV_SQRT_BITS (8 * sizeof(u16)) /* or sizeof_in_bits(rec_inv_sqrt) */
++/* needed shift to get a Q0.32 number from rec_inv_sqrt */
++#define REC_INV_SQRT_SHIFT (32 - REC_INV_SQRT_BITS)
++
+ /**
+  * struct codel_stats - contains codel shared variables and stats
+  * @maxpacket:	largest packet we've seen so far
+@@ -173,17 +177,18 @@ static void codel_stats_init(struct code
+  * http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots
+  * new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
+  *
+- * Here, invsqrt is a fixed point number (< 1.0), 31bit mantissa)
++ * Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
+  */
+ static void codel_Newton_step(struct codel_vars *vars)
+ {
+-	u32 invsqrt = vars->rec_inv_sqrt;
+-	u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 31;
+-	u64 val = (3LL << 31) - ((u64)vars->count * invsqrt2);
++	u32 invsqrt = ((u32)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
++	u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 32;
++	u64 val = (3LL << 32) - ((u64)vars->count * invsqrt2);
+ 
+-	val = (val * invsqrt) >> 32;
++	val >>= 2; /* avoid overflow in following multiply */
++	val = (val * invsqrt) >> (32 - 2 + 1);
+ 
+-	vars->rec_inv_sqrt = val;
++	vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
+ }
+ 
+ /*
+@@ -195,7 +200,7 @@ static codel_time_t codel_control_law(co
+ 				      codel_time_t interval,
+ 				      u32 rec_inv_sqrt)
+ {
+-	return t + reciprocal_divide(interval, rec_inv_sqrt << 1);
++	return t + reciprocal_divide(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
+ }
+ 
+ 
+@@ -326,7 +331,7 @@ static struct sk_buff *codel_dequeue(str
+ 			codel_Newton_step(vars);
+ 		} else {
+ 			vars->count = 1;
+-			vars->rec_inv_sqrt = 0x7fffffff;
++			vars->rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
+ 		}
+ 		vars->lastcount = vars->count;
+ 		vars->drop_next = codel_control_law(now, params->interval,