Anton,
we've just built a digital GigEVision camera based on a MPC8343 running
at 266/400 csb/core speed.
Transmission is done from a kernel module that allocates skb into which
the image data is DMA'd by an external PCI master.
As soon as the image data is complete all buffers are sent out via
dev->hard_start_xmit ...
Bandwidth is currently 1.3MPixel @ 50Hz which give 65MBytes/sec
(~520MBit/s).
Of course it's UDP _without_ checksumming ....
Actually I have no sensor available that gives higher bandwidth ... but
having a look at transmission time I'm sure the MPC8343 can easily go up
to +800MBit.
Obviously your cpu time is consumed on a higher level.
Cheers,
André
Anton Vorontsov wrote:
Hi all,
Down here few question regarding networking throughput, I would
appreciate any thoughts or ideas.
On the MPC8315E-RDB board (CPU at 400MHz, CSB at 133 MHz) I'm observing
relatively low TCP throughput using gianfar driver...
The maximum value I've seen with the current kernels is 142 Mb/s of TCP
and 354 Mb/s of UDP (NAPI and interrupts coalescing enabled):
[EMAIL PROTECTED]:~# netperf -l 10 -H 10.0.1.1 -t TCP_STREAM -- -m 32768 -s
157344 -S 157344
TCP STREAM TEST to 10.0.1.1
#Cpu utilization 0.10
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
206848 212992 32768 10.00 142.40
[EMAIL PROTECTED]:~# netperf -l 10 -H 10.0.1.1 -t UDP_STREAM -- -m 32768 -s
157344 -S 157344
UDP UNIDIRECTIONAL SEND TEST to 10.0.1.1
#Cpu utilization 100.00
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
212992 32768 10.00 13539 0 354.84
206848 10.00 13539 354.84
Is this normal?
netperf running in loopback gives me 329 Mb/s of TCP throughput:
[EMAIL PROTECTED]:~# netperf -l 10 -H 127.0.0.1 -t TCP_STREAM -- -m 32768 -s
157344 -S 157344
TCP STREAM TEST to 127.0.0.1
#Cpu utilization 100.00
#Cpu utilization 100.00
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
212992 212992 32768 10.00 329.60
May I consider this as a something that is close to the Linux'
theoretical maximum for this setup? Or this isn't reliable test?
I can compare with teh MPC8377E-RDB (very similar board - exactly the same
ethernet phy, the same drivers are used, i.e. everything is the same from
the ethernet stand point), but running at 666 MHz, CSB at 333MHz:
|CPU MHz|BUS MHz|UDP Mb/s|TCP Mb/s|
------------------------------------------
MPC8377| 666| 333| 646| 264|
MPC8315| 400| 133| 354| 142|
------------------------------------------
RATIO | 1.6| 2.5| 1.8| 1.8|
It seems that things are really dependant on the CPU/CSB speed.
I've tried to tune gianfar driver in various ways... and it gave
some positive results with this patch:
diff --git a/drivers/net/gianfar.h b/drivers/net/gianfar.h
index fd487be..b5943f9 100644
--- a/drivers/net/gianfar.h
+++ b/drivers/net/gianfar.h
@@ -123,8 +123,8 @@ extern const char gfar_driver_version[];
#define GFAR_10_TIME 25600
#define DEFAULT_TX_COALESCE 1
-#define DEFAULT_TXCOUNT 16
-#define DEFAULT_TXTIME 21
+#define DEFAULT_TXCOUNT 80
+#define DEFAULT_TXTIME 105
#define DEFAULT_RXTIME 21
Basically this raises the tx interrupts coalescing threshold (raising
it more didn't help, as well as didn't help raising rx thresholds).
Now:
[EMAIL PROTECTED]:~# netperf -l 3 -H 10.0.1.1 -t TCP_STREAM -- -m 32768 -s
157344 -S 157344
TCP STREAM TEST to 10.0.1.1
#Cpu utilization 100.00
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
206848 212992 32768 3.00 163.04
That is +21 Mb/s (14% up). Not fantastic, but good anyway.
As expected, the latency increased too:
Before the patch:
--- 10.0.1.1 ping statistics ---
20 packets transmitted, 20 received, 0% packet loss, time 18997ms
rtt min/avg/max/mdev = 0.108/0.124/0.173/0.022 ms
After:
--- 10.0.1.1 ping statistics ---
22 packets transmitted, 22 received, 0% packet loss, time 20997ms
rtt min/avg/max/mdev = 0.158/0.167/0.182/0.004 ms
34% up... heh. Should we sacrifice the latency in favour of throughput?
Is 34% latency growth bad thing? What is worse, lose 21 Mb/s or 34% of
latency? ;-)
Thanks in advance,
p.s. Btw, the patch above helps even better on the on the -rt kernels,
since on the -rt kernels the throughput is near 100 Mb/s, with the
patch the throughput is close to 140 Mb/s.
MATRIX VISION GmbH, Talstraße 16, DE-71570 Oppenweiler - Registergericht:
Amtsgericht Stuttgart, HRB 271090
Geschäftsführer: Gerhard Thullner, Werner Armingeon, Uwe Furtner
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
