diff options
Diffstat (limited to 'target/linux/generic/patches-3.3/045-codel-use-u16-field-instead-of-31bits-for-rec_inv_sq.patch')
| -rw-r--r-- | target/linux/generic/patches-3.3/045-codel-use-u16-field-instead-of-31bits-for-rec_inv_sq.patch | 86 |
1 files changed, 0 insertions, 86 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 deleted file mode 100644 index 933a3dcdaf..0000000000 --- a/target/linux/generic/patches-3.3/045-codel-use-u16-field-instead-of-31bits-for-rec_inv_sq.patch +++ /dev/null @@ -1,86 +0,0 @@ -From 03333931c17d9c62ba4063d4e4fec1578c0729a7 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] codel: use u16 field instead of 31bits for rec_inv_sqrt - -commit 6ff272c9ad65eda219cd975b9da2dbc31cc812ee upstream. - -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, |