large divisor for flow classifier
Subsystems (3)
It appears that when setting a fairly large divisor on the flow classifier for sfq, traffic stops altogether.
On my machine, anything above divisor 2200 seems to stop all traffic. If I want to be fair between hosts (but not flows) for a large network (say 6000 hosts), I run into problems. Obviously the rates here are quite low but this is just an example.
I also tested on a real interface with the same results.
Example that works:
tc qdisc add dev ifb0 root handle 3: htb default 10
tc class add dev ifb0 parent 3: classid 3:1 htb rate 80kbit
tc class add dev ifb0 parent 3:1 classid 3:10 htb rate 80kbit
tc qdisc add dev ifb0 parent 3:10 handle 310: sfq perturb 10
tc filter add dev ifb0 parent 3: protocol all prio 1 u32 match mark 0x000 0xf00 flowid 3:10 tc filter add dev ifb0 parent 310: protocol all handle 0x310 flow hash keys dst divisor 1024
Example that doesn't work:
tc qdisc add dev ifb0 root handle 3: htb default 10
tc class add dev ifb0 parent 3: classid 3:1 htb rate 80kbit
tc class add dev ifb0 parent 3:1 classid 3:10 htb rate 80kbit
tc qdisc add dev ifb0 parent 3:10 handle 310: sfq perturb 10
tc filter add dev ifb0 parent 3: protocol all prio 1 u32 match mark 0x000 0xf00 flowid 3:10 tc filter add dev ifb0 parent 310: protocol all handle 0x310 flow hash keys dst divisor 6144
Jonathan
Quoted 15 lines · Jonathan Thibault
It appears that when setting a fairly large divisor on the flow classifier for sfq, traffic stops altogether.
On my machine, anything above divisor 2200 seems to stop all traffic. If I want to be fair between hosts (but not flows) for a large network (say 6000 hosts), I run into problems. Obviously the rates here are quite low but this is just an example.
I also tested on a real interface with the same results.
Example that works:
tc qdisc add dev ifb0 root handle 3: htb default 10
tc class add dev ifb0 parent 3: classid 3:1 htb rate 80kbit
tc class add dev ifb0 parent 3:1 classid 3:10 htb rate 80kbit
tc qdisc add dev ifb0 parent 3:10 handle 310: sfq perturb 10
tc filter add dev ifb0 parent 3: protocol all prio 1 u32 match mark0x0000xf00flowid 3:10 tc filter add dev ifb0 parent 310: protocol all handle0x310flow hash keys dst divisor 1024
Quoted 9 lines
Example that doesn't work:
tc qdisc add dev ifb0 root handle 3: htb default 10
tc class add dev ifb0 parent 3: classid 3:1 htb rate 80kbit
tc class add dev ifb0 parent 3:1 classid 3:10 htb rate 80kbit
tc qdisc add dev ifb0 parent 3:10 handle 310: sfq perturb 10
tc filter add dev ifb0 parent 3: protocol all prio 1 u32 match mark0x0000xf00flowid 3:10 tc filter add dev ifb0 parent 310: protocol all handle0x310flow hash keys dst divisor 6144
SFQ is limited to a 1024 divisor
You might try following patch :
(8192 is the smallest power of two greater than 6144)
sizeof(struct sfq_sched_data) becomes 0x2ccc instead of 0x10cc
keep in mind hash distribution is not perfect.
What would be the real rate ?
net/sched/sch_sfq.c +1 -1
@@ -77,7 +77,7 @@It is easy to increase these values, but not in flight. */ #define SFQ_DEPTH 128 -#define SFQ_HASH_DIVISOR 1024 +#define SFQ_HASH_DIVISOR 8192/* This type should contain at least SFQ_DEPTH*2 values */ typedef unsigned char sfq_index ;
Quoted 4 lines · Eric Dumazet
Quoted 3 lines · Jonathan Thibault
It appears that when setting a fairly large divisor on the flow classifier for sfq, traffic stops altogether.
On my machine, anything above divisor 2200 seems to stop all traffic. If I want to be fair between hosts (but not flows) for a large network (say 6000 hosts), I run into problems. Obviously the rates here are quite low but this is just an example.
...
Quoted 18 lines
SFQ is limited to a 1024 divisor
You might try following patch :
(8192 is the smallest power of two greater than 6144)
sizeof(struct sfq_sched_data)becomes0x2cccinstead of0x10cckeep in mind hash distribution is not perfect.
What would be the real rate ?
net/sched/sch_sfq.c +0
-0
net/sched/sch_sfq.c line 80
Quoted 5 lines
net/sched/sch_sfq.c +1
-1@@ -77,7 +77,7 @@It is easy to increase these values, but not in flight. */ #define SFQ_DEPTH 128 -#define SFQ_HASH_DIVISOR 1024 +#define SFQ_HASH_DIVISOR 8192
Because of low SFQ_DEPTH, which limits its queue to 127 packets, SFQ isn't suitable for serving so many users. There is sch_drr as a replacement, alas more complex and undocumented, but google should help you enough.
Jarek P.
Quoted 3 lines · Jarek Poplawski
Because of low
SFQ_DEPTH, which limits its queue to 127 packets, SFQ isn't suitable for serving so many users. There issch_drras a replacement, alas more complex and undocumented [...]
Sorry! Actually there is a man page already!
Kudos to Florian!
Jarek P.
I will certainly look into that.
Jonathan
Quoted 10 lines · Jarek Poplawski
Eric Dumazet wrote:
Because of low
SFQ_DEPTH, which limits its queue to 127 packets, SFQ isn't suitable for serving so many users. There issch_drras a replacement, alas more complex and undocumented, but google should help you enough.Jarek P.
Merci beaucoup :),
It at least shows I wasn't just confused about the way it works. In its planned final form, the rate will be set around 175Mbit. I don't need perfect distribution so things should be fine as long as hosts cannot easily cheat their way into having more bandwidth merely by creating more flows.
Jonathan
Quoted 30 lines · Eric Dumazet
Le vendredi 15 octobre 2010 à 14:14 -0400, Jonathan Thibault a écrit :
SFQ is limited to a 1024 divisor
You might try following patch :
(8192 is the smallest power of two greater than 6144)
sizeof(struct sfq_sched_data)becomes0x2cccinstead of0x10cckeep in mind hash distribution is not perfect.
What would be the real rate ?
net/sched/sch_sfq.c +1
-1@@ -77,7 +77,7 @@It is easy to increase these values, but not in flight. */ #define SFQ_DEPTH 128 -#define SFQ_HASH_DIVISOR 1024 +#define SFQ_HASH_DIVISOR 8192/* This type should contain at least SFQ_DEPTH*2 values */ typedef unsigned char sfq_index ;