Commit Graph

13 Commits

Author SHA1 Message Date
Eric Dumazet
ddecf0f4db net_sched: sfq: add optional RED on top of SFQ
Adds an optional Random Early Detection on each SFQ flow queue.

Traditional SFQ limits count of packets, while RED permits to also
control number of bytes per flow, and adds ECN capability as well.

1) We dont handle the idle time management in this RED implementation,
since each 'new flow' begins with a null qavg. We really want to address
backlogged flows.

2) if headdrop is selected, we try to ecn mark first packet instead of
currently enqueued packet. This gives faster feedback for tcp flows
compared to traditional RED [ marking the last packet in queue ]

Example of use :

tc qdisc add dev $DEV parent 1:1 handle 10: est 1sec 4sec sfq \
	limit 3000 headdrop flows 512 divisor 16384 \
	redflowlimit 100000 min 8000 max 60000 probability 0.20 ecn

qdisc sfq 10: parent 1:1 limit 3000p quantum 1514b depth 127 headdrop
flows 512/16384 divisor 16384
 ewma 6 min 8000b max 60000b probability 0.2 ecn
 prob_mark 0 prob_mark_head 4876 prob_drop 6131
 forced_mark 0 forced_mark_head 0 forced_drop 0
 Sent 1175211782 bytes 777537 pkt (dropped 6131, overlimits 11007
requeues 0)
 rate 99483Kbit 8219pps backlog 689392b 456p requeues 0

In this test, with 64 netperf TCP_STREAM sessions, 50% using ECN enabled
flows, we can see number of packets CE marked is smaller than number of
drops (for non ECN flows)

If same test is run, without RED, we can check backlog is much bigger.

qdisc sfq 10: parent 1:1 limit 3000p quantum 1514b depth 127 headdrop
flows 512/16384 divisor 16384
 Sent 1148683617 bytes 795006 pkt (dropped 0, overlimits 0 requeues 0)
 rate 98429Kbit 8521pps backlog 1221290b 841p requeues 0

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Stephen Hemminger <shemminger@vyatta.com>
CC: Dave Taht <dave.taht@gmail.com>
Tested-by: Dave Taht <dave.taht@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2012-01-12 20:05:28 -08:00
Eric Dumazet
eeca6688d6 net_sched: red: split red_parms into parms and vars
This patch splits the red_parms structure into two components.

One holding the RED 'constant' parameters, and one containing the
variables.

This permits a size reduction of GRED qdisc, and is a preliminary step
to add an optional RED unit to SFQ.

SFQRED will have a single red_parms structure shared by all flows, and a
private red_vars per flow.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Dave Taht <dave.taht@gmail.com>
CC: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2012-01-05 14:01:21 -05:00
Eric Dumazet
a73ed26bba sch_red: generalize accurate MAX_P support to RED/GRED/CHOKE
Now RED uses a Q0.32 number to store max_p (max probability), allow
RED/GRED/CHOKE to use/report full resolution at config/dump time.

Old tc binaries are non aware of new attributes, and still set/get Plog.

New tc binary set/get both Plog and max_p for backward compatibility,
they display "probability value" if they get max_p from new kernels.

# tc -d  qdisc show dev ...
...
qdisc red 10: parent 1:1 limit 360Kb min 30Kb max 90Kb ecn ewma 5
probability 0.09 Scell_log 15

Make sure we avoid potential divides by 0 in reciprocal_value(), if
(max_th - min_th) is big.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-12-09 13:46:15 -05:00
Eric Dumazet
8af2a218de 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>
2011-12-08 19:52:43 -05:00
Eric Dumazet
ea6a5d3b97 sch_red: fix red_calc_qavg_from_idle_time
Since commit a4a710c4a7 (pkt_sched: Change PSCHED_SHIFT from 10 to
6) it seems RED/GRED are broken.

red_calc_qavg_from_idle_time() computes a delay in us units, but this
delay is now 16 times bigger than real delay, so the final qavg result
smaller than expected.

Use standard kernel time services since there is no need to obfuscate
them.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-11-30 23:27:22 -05:00
stephen hemminger
838b4dc6d8 sched: remove unused backlog in RED stats
The RED statistics structure includes backlog field which is not
set or used by any code.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-01-12 19:00:39 -08:00
Eric Dumazet
fd2c3ef761 net: cleanup include/net
This cleanup patch puts struct/union/enum opening braces,
in first line to ease grep games.

struct something
{

becomes :

struct something {

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-11-04 05:06:25 -08:00
Patrick McHardy
3bebcda280 [NET_SCHED]: turn PSCHED_GET_TIME into inline function
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:27:55 -07:00
Patrick McHardy
03cc45c0a5 [NET_SCHED]: turn PSCHED_TDIFF_SAFE into inline function
Also rename to psched_tdiff_bounded.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:27:54 -07:00
Patrick McHardy
a084980dcb [NET_SCHED]: kill PSCHED_SET_PASTPERFECT/PSCHED_IS_PASTPERFECT
Use direct assignment and comparison instead.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:27:51 -07:00
Ilpo Järvinen
c4c0ce5c57 [PKT_SCHED] RED: Fix overflow in calculation of queue average
Overflow can occur very easily with 32 bits, e.g., with 1 second
us_idle is approx. 2^20, which leaves only 11-Wlog bits for queue
length. Since the EWMA exponent is typically around 9, queue
lengths larger than 2^2 cause overflow. Whether the affected
branch is taken when us_idle is as high as 1 second, depends on
Scell_log, but with rather reasonable configuration Scell_log is
large enough to cause p->Stab to have zero index, which always
results zero shift (typically also few other small indices result
in zero shift).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-08-04 22:59:51 -07:00
David Woodhouse
62c4f0a2d5 Don't include linux/config.h from anywhere else in include/
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
2006-04-26 12:56:16 +01:00
Thomas Graf
a783474591 [PKT_SCHED]: Generic RED layer
Extracts the RED algorithm from sch_red.c and puts it into include/net/red.h
for use by other RED based modules. The statistics are extended to be more
fine grained in order to differ between probability/forced marks/drops.
We now reset the average queue length when setting new parameters, leaving
it might result in an unreasonable qavg for a while depending on the value of W.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
2005-11-05 22:02:24 +01:00