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

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Message-ID: <1320819875.26025.48.camel@edumazet-laptop>
Date:	Wed, 09 Nov 2011 07:24:35 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Manavalan Krishnan <manavalan_k@...oo.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: Large file copy to NFS mounted directory causes delay in other
 application packets

Le mardi 08 novembre 2011 à 21:28 -0800, Manavalan Krishnan a écrit :
> Hi All
> 
> I have two systems with two network interfaces each(eth0 and eth1). I
> am running linux-HA (heartbeat deamon) on both the systems and they
> use eth0 for exchanging heartbeats. I have NFS mounted directory in
> one system and the NFS client uses the interface eth1. 
> 
> I try to copy a large file to NFS mounted directory. But the heartbeat
> daemons misses the heartbeat packets from peers while copy is under
> progress. I did tcpdump and found that the heartbeat packets are
> delayed for few seconds before sent out on eth0. When I stop the file
> copy, the heartbeats are delivered properly. It seems linux kernel
> somehow giving priority for NFS packets(generated from the file copy)
> over other application packets.
> 
> Any thoughts on this behavior? Is there any way we can avoid this so
> that application packets get equal chance while large file copy to NFS
> mounted directory under progress?
> 
CC netdev

1) Is your NFS using UDP or TCP ?
2) Is your eth0 dedicated to heartbeats and eth1 to NFS traffic ?
3) How do you know heartbeats are delayed ?
4) Is your server CPU bounded ?

Thanks


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