[mythtv-users] HDHomeRun Hint: Ethernet buffer size
Jon Boehm
boehm100 at comcast.net
Tue Sep 4 19:22:15 UTC 2007
Hi,
I was getting horrible pixelation, missing time, dropped channel locks,
and strange slow motion artifacts from some of my 1080i channels. I'm
pretty sure I have fixed the problem now. I turns out my Ethernet
buffers were overflowing. I have a F/B machine with 4 tuners total.
When recording and commercial scanning the machine maxes out.
The silicon dust how-to mentions this:
Packet loss ¶
On slower machines or machines under high load the maximum receive
socket buffer size for the system should be increased to 1MB:
sysctl -w net.core.rmem_max=1048576
-----------
While this is all that may be required I did some searching and ended up
doing this since I have plenty of RAM:
This is my sysctl.conf file
#increase TCP maximum buffer size
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
# increase linux autotuning TCP buffer limits
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216
# don't cache ssthresh from previous connection
net.ipv4.tcp_no_metrics_save = 1
# recommended to increase this for 1000 BT or higher
net.core.netdev_max_backlog = 2500
Once you change these run the command
sudo sysctl -p
A link about this.
http://dsd.lbl.gov/TCP-tuning/linux.html
A couple others I use
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_sack =1
net.ipv4.tcp_window_scaling = 1
Another link
http://www.speedguide.net/read_articles.php?id=121
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