netdev - Re: Large file copy to NFS mounted directory causes delay in other application packets

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Date:	Wed, 9 Nov 2011 00:42:31 -0800 (PST)
From:	Manavalan Krishnan <manavalan_k@...oo.com>
To:	Dave Taht <dave.taht@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: Large file copy to NFS mounted directory causes delay in other application packets

>When I see behavior like this I keep thinking interactions between overlarge large txqueuelens, somewhat busted TCP offloads on NICs, and that pfifo_fast must die in favor of fair queuing and/or diffserv classification. But seeing >it on two different nics implies that your switch (which I assume is shared) is possibly to blame...
>(I see bufferbloat everywhere, but mostly because it's what I work on)

>Is this NFS over TCP? Does the HA daemons prioritize packets at all? Does your switch? Does your qdiscs? How deep are your buffers on the network cards and txqueuelens and switch? 
>(eric's other questions below are probably more valid)


HA   daemons does not prioritize. could you please provide info on how to prioritize application packets?
We tried with different switches, the same problem occurs. so switch may not be the issue here.
switch and qdisks does not prirotize the packets.
Here are network buffers used in the servers

txqueuelen is 1000 

net.core.netdev_max_backlog = 1000
net.core.rmem_default = 262144
net.core.rmem_max = 262144
net.core.wmem_default = 129024
net.core.wmem_max = 131071
net.ipv4.tcp_rmem = 4096    87380    4194304
net.ipv4.tcp_wmem = 4096    16384    4194304
net.ipv4.tcp_mem = 196608    262144    393216

Thanks
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