trying to understand the "net.core.wmem_default" parameter

["a s p a s i a" <aspasia pair com>]

hello,

can someone please explain simply what
the "net.core.wmem_default" parameter
in /etc/sysctl.conf exactly affect?

an example:

# increase Linux TCP buffer limits
net.core.rmem_max = 8388608
net.core.wmem_max = 8388608
net.core.rmem_default = 65536
net.core.wmem_default = 65536

Questions:

1. rmem and wmem - defaults - someone mentioned is:
 TCP send and receive socket buffer sizes:
"It is essentially the maximum size of the linked list that is used to
hold the socket buffers for a particular connection."

what exactly does this mean?  is this the congestion window
for TCP only packets?  What if my application is running UDP -
will changing/tuning the above parameters matter?

2.  Is it a true statement to say:

Conventionally value for buffers used for reading network values are twice
the value for writes as the reads are interrupt driven and therefore flow
control cannot be imposed....As writes can be controlled by the host O/S
then the kernel can make the application block.

again, what if my application is running UDP not TCP, does the
above statement still hold true?


thanks in advance,

- a.


a s p a s i a
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