Patchwork [5/5] tc: man: add man page for drr scheduler

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Submitter Florian Westphal
Date Jan. 12, 2010, 8:45 p.m.
Message ID <1263329126-19756-1-git-send-email-fw@strlen.de>
Download mbox | patch
Permalink /patch/42768/
State Accepted
Delegated to: stephen hemminger
Headers show

Comments

Florian Westphal - Jan. 12, 2010, 8:45 p.m.
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 man/man8/tc-drr.8 |   89 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 man/man8/tc.8     |    1 +
 2 files changed, 90 insertions(+), 0 deletions(-)
 create mode 100644 man/man8/tc-drr.8
Patrick McHardy - Jan. 13, 2010, 5:34 a.m.
Florian Westphal wrote:

Thanks Florian. A few minor suggestions below.

> diff --git a/man/man8/tc-drr.8 b/man/man8/tc-drr.8
> new file mode 100644
> index 0000000..5fcb0eb
> --- /dev/null
> +++ b/man/man8/tc-drr.8
> @@ -0,0 +1,89 @@
> +.TH TC 8 "January 2010" "iproute2" "Linux"
> +.SH NAME
> +drr \- deficit round robin scheduler
> +.SH SYNOPSIS
> +.B tc qdisc ... add drr
> +.B [ quantum
> +bytes
> +.B ]
> +
> +.SH DESCRIPTION
> +
> +The Deficit Round Robin Scheduler is a classful queuing discipline as
> +a more flexible replacement for Stochastic Fairness Queuing.
> +
> +Unlike SFQ, there are no built-in queues \-\- you need to add classes
> +and then set up filters to classify packets accordingly.
> +This can be useful e.g. for using RED qdiscs with different settings for particular
> +traffic. There is no default class \-\- if a packet cannot be classified,
> +it is dropped.
> +
> +.SH ALGORITHM
> +Each class is assigned a deficit counter, initialized to
> +.B quantum.
> +
> +DRR maintains an (internal) ''active'' list of classes whose qdiscs are
> +non-empty.  This list is used for dequeuing.  A packet is dequeued from
> +the class at the head of the list if the packet size is smaller or equal
> +to the deficit counter.  If the counter is too small, it is increased by
> +.B quantum
> +and the scheduler moves on to the next class in the active list.
> +
> +
> +.SH PARAMETERS
> +.TP
> +quantum
> +Amount of bytes a flow is allowed to dequeue before the scheduler moves to the next.

next class or next flow?

> +Defaults to the MTU of the interface. The minimum value is 1.
> +
> +.SH EXAMPLE & USAGE
> +
> +To attach to device eth0, using the interface MTU as its quantum:
> +.P
> +# tc qdisc add dev eth0 handle 1 root drr
> +.P
> +Adding two classes:
> +.P
> +# tc class add dev eth0 parent 1: classid 1:1 drr
> +# tc class add dev eth0 parent 1: classid 1:2 drr
> +.P
> +You also need to add at least one filter to classify packets.
> +.P
> +# tc filter add dev eth0 protocol .. classid 1:1
> +.P
> +
> +Like SFQ, DRR is only useful when it owns the queue \-\- it is a pure scheduler and does
> +not delay packets.  Attaching non-work-conserving qdiscs like tbf to it does not make
> +sense \-\- other qdiscs in the active list will also become inactive until the dequeue
> +operation succeeds.  Embed DRR within another qdisc like HTB or HFSC to ensure it owns the queue.
> +.P
> +You can mimic SFQ behavior by assigning packets to the attached classes using the
> +hash filter:

flow filter

> +
> +.B tc qdisc add dev .. drr
> +.B for i in .. 1024;do
> +.B   tc class add dev ..  classid $handle:$(print %x $i)
> +.B   tc qdisc add dev .. fifo limit 16
> +.B done
> +.B tc filter add .. protocol ip .. $handle flow hash keys src,dst divisor 1024 perturb 10

To mimic SFQ, the filter needs to use "keys
src,dst,proto,proto-src,proto-dst".

> +
> +
> +.SH SOURCE
> +.TP
> +o
> +M. Shreedhar and George Varghese "Efficient Fair
> +Queuing using Deficit Round Robin", Proc. SIGCOMM 95.
> +
> +.SH NOTES
> +
> +This implementation does not drop packets from the longest queue on overrun,
> +as limits are handled by the individual child qdiscs.
> +
> +.SH SEE ALSO
> +.BR tc (8),
> +.BR tc-htb (8),
> +.BR tc-sfq (8)
> +
> +.SH AUTHOR
> +sched_drr was written by Patrick McHardy.
> +
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Florian Westphal - Jan. 13, 2010, 8:27 a.m.
Patrick McHardy <kaber@trash.net> wrote:
> Thanks Florian. A few minor suggestions below.

Thanks Patrick, I'll add all of your suggestions
to the man page in the next round of this patch.

I'll wait a few days, maybe someone else has other ideas.

Thanks again for reviewing,
Florian
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Patch

diff --git a/man/man8/tc-drr.8 b/man/man8/tc-drr.8
new file mode 100644
index 0000000..5fcb0eb
--- /dev/null
+++ b/man/man8/tc-drr.8
@@ -0,0 +1,89 @@ 
+.TH TC 8 "January 2010" "iproute2" "Linux"
+.SH NAME
+drr \- deficit round robin scheduler
+.SH SYNOPSIS
+.B tc qdisc ... add drr
+.B [ quantum
+bytes
+.B ]
+
+.SH DESCRIPTION
+
+The Deficit Round Robin Scheduler is a classful queuing discipline as
+a more flexible replacement for Stochastic Fairness Queuing.
+
+Unlike SFQ, there are no built-in queues \-\- you need to add classes
+and then set up filters to classify packets accordingly.
+This can be useful e.g. for using RED qdiscs with different settings for particular
+traffic. There is no default class \-\- if a packet cannot be classified,
+it is dropped.
+
+.SH ALGORITHM
+Each class is assigned a deficit counter, initialized to
+.B quantum.
+
+DRR maintains an (internal) ''active'' list of classes whose qdiscs are
+non-empty.  This list is used for dequeuing.  A packet is dequeued from
+the class at the head of the list if the packet size is smaller or equal
+to the deficit counter.  If the counter is too small, it is increased by
+.B quantum
+and the scheduler moves on to the next class in the active list.
+
+
+.SH PARAMETERS
+.TP
+quantum
+Amount of bytes a flow is allowed to dequeue before the scheduler moves to the next.
+Defaults to the MTU of the interface. The minimum value is 1.
+
+.SH EXAMPLE & USAGE
+
+To attach to device eth0, using the interface MTU as its quantum:
+.P
+# tc qdisc add dev eth0 handle 1 root drr
+.P
+Adding two classes:
+.P
+# tc class add dev eth0 parent 1: classid 1:1 drr
+# tc class add dev eth0 parent 1: classid 1:2 drr
+.P
+You also need to add at least one filter to classify packets.
+.P
+# tc filter add dev eth0 protocol .. classid 1:1
+.P
+
+Like SFQ, DRR is only useful when it owns the queue \-\- it is a pure scheduler and does
+not delay packets.  Attaching non-work-conserving qdiscs like tbf to it does not make
+sense \-\- other qdiscs in the active list will also become inactive until the dequeue
+operation succeeds.  Embed DRR within another qdisc like HTB or HFSC to ensure it owns the queue.
+.P
+You can mimic SFQ behavior by assigning packets to the attached classes using the
+hash filter:
+
+.B tc qdisc add dev .. drr
+.B for i in .. 1024;do
+.B   tc class add dev ..  classid $handle:$(print %x $i)
+.B   tc qdisc add dev .. fifo limit 16
+.B done
+.B tc filter add .. protocol ip .. $handle flow hash keys src,dst divisor 1024 perturb 10
+
+
+.SH SOURCE
+.TP
+o
+M. Shreedhar and George Varghese "Efficient Fair
+Queuing using Deficit Round Robin", Proc. SIGCOMM 95.
+
+.SH NOTES
+
+This implementation does not drop packets from the longest queue on overrun,
+as limits are handled by the individual child qdiscs.
+
+.SH SEE ALSO
+.BR tc (8),
+.BR tc-htb (8),
+.BR tc-sfq (8)
+
+.SH AUTHOR
+sched_drr was written by Patrick McHardy.
+
diff --git a/man/man8/tc.8 b/man/man8/tc.8
index 8c0880f..e17ce68 100644
--- a/man/man8/tc.8
+++ b/man/man8/tc.8
@@ -367,6 +367,7 @@  print rates in IEC units (ie. 1K = 1024).
 was written by Alexey N. Kuznetsov and added in Linux 2.2.
 .SH SEE ALSO
 .BR tc-cbq (8),
+.BR tc-drr (8),
 .BR tc-htb (8),
 .BR tc-sfq (8),
 .BR tc-red (8),