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- New sysctl variable: net.inet.ip.dummynet.io_fast

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If it is set to zero value (default) dummynet module will try to emulate
  real link as close as possible (bandwidth & latency): packet will not leave
  pipe faster than it should be on real link with given bandwidth.
  (This is original behaviour of dummynet which was altered in previous commit)
  If it is set to non-zero value only bandwidth is enforced: packet's latency
  can be lower comparing to real link with given bandwidth.

- Document recently introduced dummynet(4) sysctl variables.

Requested by:	luigi, julian
MFC after:	3 month
This commit is contained in:
Oleg Bulyzhin 2007-11-17 21:54:57 +00:00
parent 796677a89e
commit 8d1e3aed2d
2 changed files with 25 additions and 4 deletions
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20
sbin/ipfw/ipfw.8
View File

@ -1,7 +1,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd October 19, 2007
.Dd November 17, 2007
.Dt IPFW 8
.Os
.Sh NAME
@ -1756,6 +1756,16 @@ Depending on local policies, a flow can contain packets for a single
TCP connection, or from/to a given host, or entire subnet, or a
protocol type, etc.
.Pp
There are two modes of dummynet operation: normal and fast.
Normal mode tries to emulate real link: dummynet scheduler ensures packet will
not leave pipe faster than it would be on real link with given bandwidth.
Fast mode allows certain packets to bypass dummynet scheduler (if packet flow
does not exceed pipe's bandwidth). Thus fast mode requires less cpu cycles
per packet (in average) but packet latency can be significantly lower comparing
to real link with same bandwidth. Default is normal mode, fast mode can be
enabled by setting net.inet.ip.dummynet.io_fast sysctl(8) variable to non-zero
value.
.Pp
Packets belonging to the same flow are then passed to either of two
different objects, which implement the traffic regulation:
.Bl -hang -offset XXXX
@ -2120,6 +2130,14 @@ Default size of the hash table used for dynamic pipes/queues.
This value is used when no
.Cm buckets
option is specified when configuring a pipe/queue.
.It Em net.inet.ip.dummynet.io_fast : No 0
If set to non-zero value enables "fast" mode of dummynet operation (see above).
.It Em net.inet.ip.dummynet.io_pkt
Number of packets passed to by dummynet.
.It Em net.inet.ip.dummynet.io_pkt_drop
Number of packets dropped by dummynet.
.It Em net.inet.ip.dummynet.io_pkt_fast
Number of packets bypassed dummynet scheduler.
.It Em net.inet.ip.dummynet.max_chain_len : No 16
Target value for the maximum number of pipes/queues in a hash bucket.
The product

9
sys/netinet/ip_dummynet.c
View File

@ -110,6 +110,7 @@ static long tick_lost; /* Lost(coalesced) ticks number. */
/* Adjusted vs non-adjusted curr_time difference (ticks). */
static long tick_diff;
static int io_fast;
static unsigned long io_pkt;
static unsigned long io_pkt_fast;
static unsigned long io_pkt_drop;
@ -185,6 +186,8 @@ SYSCTL_LONG(_net_inet_ip_dummynet, OID_AUTO, tick_diff,
SYSCTL_LONG(_net_inet_ip_dummynet, OID_AUTO, tick_lost,
CTLFLAG_RD, &tick_lost, 0,
"Number of ticks coalesced by dummynet taskqueue.");
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, io_fast,
CTLFLAG_RW, &io_fast, 0, "Enable fast dummynet io.");
SYSCTL_ULONG(_net_inet_ip_dummynet, OID_AUTO, io_pkt,
CTLFLAG_RD, &io_pkt, 0,
"Number of packets passed to dummynet.");
@ -967,7 +970,7 @@ create_queue(struct dn_flow_set *fs, int i)
q->hash_slot = i;
q->next = fs->rq[i];
q->S = q->F + 1; /* hack - mark timestamp as invalid. */
q->numbytes = fs->pipe->bandwidth;
q->numbytes = io_fast ? fs->pipe->bandwidth : 0;
fs->rq[i] = q;
fs->rq_elements++;
return (q);
@ -1325,7 +1328,7 @@ dummynet_io(struct mbuf **m0, int dir, struct ip_fw_args *fwa)
goto done;
if (q->q_time < curr_time)
q->numbytes = fs->pipe->bandwidth;
q->numbytes = io_fast ? fs->pipe->bandwidth : 0;
q->q_time = curr_time;
/*
@ -1736,7 +1739,7 @@ config_pipe(struct dn_pipe *p)
/* Flush accumulated credit for all queues. */
for (i = 0; i <= pipe->fs.rq_size; i++)
for (q = pipe->fs.rq[i]; q; q = q->next)
q->numbytes = p->bandwidth;
q->numbytes = io_fast ? p->bandwidth : 0;
pipe->bandwidth = p->bandwidth;
pipe->numbytes = 0; /* just in case... */