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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-12-08 10:06:03 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-12-09 04:52:43 +0400 |
| commit | 8af2a218de38f51ea4b4fa48cac1273319ae260c (patch) | |
| tree | 07a4557322b79878096172355fb02ab2bae3f432 /include/linux/pkt_sched.h | |
| parent | 57459185a19b0246866479522b77cbb9732201d1 (diff) | |
| download | linux-8af2a218de38f51ea4b4fa48cac1273319ae260c.tar.xz | |
sch_red: Adaptative RED AQM
Adaptative RED AQM for linux, based on paper from Sally FLoyd,
Ramakrishna Gummadi, and Scott Shenker, August 2001 :
http://icir.org/floyd/papers/adaptiveRed.pdf
Goal of Adaptative RED is to make max_p a dynamic value between 1% and
50% to reach the target average queue : (max_th - min_th) / 2
Every 500 ms:
if (avg > target and max_p <= 0.5)
increase max_p : max_p += alpha;
else if (avg < target and max_p >= 0.01)
decrease max_p : max_p *= beta;
target :[min_th + 0.4*(min_th - max_th),
min_th + 0.6*(min_th - max_th)].
alpha : min(0.01, max_p / 4)
beta : 0.9
max_P is a Q0.32 fixed point number (unsigned, with 32 bits mantissa)
Changes against our RED implementation are :
max_p is no longer a negative power of two (1/(2^Plog)), but a Q0.32
fixed point number, to allow full range described in Adatative paper.
To deliver a random number, we now use a reciprocal divide (thats really
a multiply), but this operation is done once per marked/droped packet
when in RED_BETWEEN_TRESH window, so added cost (compared to previous
AND operation) is near zero.
dump operation gives current max_p value in a new TCA_RED_MAX_P
attribute.
Example on a 10Mbit link :
tc qdisc add dev $DEV parent 1:1 handle 10: est 1sec 8sec red \
limit 400000 min 30000 max 90000 avpkt 1000 \
burst 55 ecn adaptative bandwidth 10Mbit
# tc -s -d qdisc show dev eth3
...
qdisc red 10: parent 1:1 limit 400000b min 30000b max 90000b ecn
adaptative ewma 5 max_p=0.113335 Scell_log 15
Sent 50414282 bytes 34504 pkt (dropped 35, overlimits 1392 requeues 0)
rate 9749Kbit 831pps backlog 72056b 16p requeues 0
marked 1357 early 35 pdrop 0 other 0
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/pkt_sched.h')
| -rw-r--r-- | include/linux/pkt_sched.h | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h index fb556dc594d3..e41e0d4de24b 100644 --- a/include/linux/pkt_sched.h +++ b/include/linux/pkt_sched.h @@ -181,6 +181,7 @@ enum { TCA_RED_UNSPEC, TCA_RED_PARMS, TCA_RED_STAB, + TCA_RED_MAX_P, __TCA_RED_MAX, }; @@ -194,8 +195,9 @@ struct tc_red_qopt { unsigned char Plog; /* log(P_max/(qth_max-qth_min)) */ unsigned char Scell_log; /* cell size for idle damping */ unsigned char flags; -#define TC_RED_ECN 1 -#define TC_RED_HARDDROP 2 +#define TC_RED_ECN 1 +#define TC_RED_HARDDROP 2 +#define TC_RED_ADAPTATIVE 4 }; struct tc_red_xstats { |