Re: [PATCH 0/1] SUNRPC: Add sysctl variables for server TCP snd/rcv buffer values

["J. Bruce Fields" <bfields@fieldses.org>]

On Fri, Jun 13, 2008 at 02:51:18PM -0400, Chuck Lever wrote:
> On Jun 12, 2008, at 5:03 PM, Dean Hildebrand wrote:
>> I think the problem there is that the only way to set the buffer size 
>> automatically would be to know the rtt and bandwidth of the network 
>> connection.  Excessive numbers of packets can get dropped if the TCP 
>> buffer is set too large for a specific network connection.
>
>> In this case, the window opens too wide and lets too many packets out 
>> into the system, somewhere along the path buffers start overflowing and 
>> packets are lost, TCP congestion avoidance kicks in and cuts the window 
>> size dramatically and performance along with it.  This type of 
>> behaviour creates a sawtooth pattern for the TCP window, which is less 
>> favourable than a more steady state pattern that is created if the TCP 
>> buffer size is set appropriately.
>
> Agreed it is a performance problem, but I thought some of the newer TCP 
> congestion algorithms were specifically designed to address this by not 
> closing the window as aggressively.
>
> Once the window is wide open, then, it would appear that choosing a good 
> congestion avoidance algorithm is also important.

Any references for Olga or I to read on that sort of behavior?

--b.