large divisor for flow classifier
Jonathan Thibault
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
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Eric Dumazet
> 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
>
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 ?
diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 3cf478d..c4a53d6 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -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;
Jarek Poplawski
> Le vendredi 15 octobre 2010 à 14:14 -0400, Jonathan Thibault a écrit :
>> 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.
> 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 ?
>
>
> diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
> index 3cf478d..c4a53d6 100644
> --- a/net/sched/sch_sfq.c
> +++ b/net/sched/sch_sfq.c
> @@ -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.
Jarek Poplawski
> 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
Sorry! Actually there is a man page already!
Kudos to Florian!
Jonathan Thibault
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
Jonathan Thibault
Jonathan
On 15/10/10 05:10 PM, Jarek Poplawski wrote: