netdev - Re: 3.4.4/amd64 full interrupt hangs under big nfs copies

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Date:	Mon, 16 Jul 2012 18:21:57 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Marc MERLIN <marc@...lins.org>
Cc:	David Miller <davem@...emloft.net>, Larry.Finger@...inger.net,
	bhutchings@...arflare.com, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: 3.4.4/amd64 full interrupt hangs under big nfs copies

On Mon, 2012-07-16 at 08:18 -0700, Marc MERLIN wrote:
> On Mon, Jul 16, 2012 at 08:18:49AM +0200, Eric Dumazet wrote:
> > > My understanding is that user space calling drivers that shut off all
> > > interrupts for extended periods of time (as least I think so since my mouse
> > > cursor would not move), is still a kernel bug.
> > > 
> > > For what it's worth, copying 1GB of data in lots of small files does not
> > > cause problems, it seems that it's big files that cause a problem since they
> > > likely fill a buffer somewhere while interrupts are disabled.
> > > 
> > > Do you have an idea of how I can find out where my mc process is stuck in
> > > the kernel?
> > > Should I reproduce with specific sysrq output?
> > 
> > Just to clarify, you get this freeze when transferring a big file from a
> > remote NFS server to your PC, (aka a download), not the reverse way ?
>  
> No, it's atually when I'm 'uploading' from my laptop to my server.
> One interesting thing is that my server is running lvm2 with snapshots,
> which makes writes slower than my laptop can push data over the network, so
> it's definitely causing buffers to fill up.
> I just did a download test and got 4.5MB/s sustained without problems.

Hmm, nfs apparently is able to push lot of data, try to reduce
rsize/wsize to sane values, like 32K instead of 512K ?

gargamel:/mnt/dshelf2/ /net/gargamel/mnt/dshelf2 nfs4
rw,nosuid,nodev,relatime,vers=4.0,rsize=524288,wsize=524288,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=192.168.205.7,local_lock=none,addr=192.168.205.3 0 0

You could trace svc_sock_setbufsize() and check how large is set
sk_sndbuf

(iwlwifi is unable to use sendpage anyway, since SG is not enabled)




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