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Subject: Re: rsize,wsize=1M causes severe lags in 10/100 Mbps
To:     Trond Myklebust <trondmy@hammerspace.com>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
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From:   Alkis Georgopoulos <alkisg@gmail.com>
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Date:   Thu, 19 Sep 2019 22:57:09 +0300
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On 9/19/19 10:51 PM, Trond Myklebust wrote:
> I don't understand why klibc would default to supplying a timeo=7
> argument at all. It would be MUCH better if it just let the kernel set
> the default, which in the case of TCP is timeo=600.
> 
> I agree with your argument that replaying requests every 0.7 seconds is
> just going to cause congestion. TCP provides for reliable delivery of
> RPC messages to the server, which is why the kernel default is a full
> minute.
> 
> So please ask the klibc developers to change libmount to let the kernel
> decide the default mount options. Their current setting is just plain
> wrong.


This was what I asked in my first message to their mailing list,
https://lists.zytor.com/archives/klibc/2019-September/004234.html

Then I realized that timeo=600 just hides the real problem,
which is rsize=1M.

NFS defaults: timeo=600,rsize=1M => lag
nfsmount defaults: timeo=7,rsize=1MK => lag AND dmesg errors

My proposal: timeo=whatever,rsize=32K => all fine

If more benchmarks are needed from me to document the
"NFS defaults: timeo=600,rsize=1M => lag"
I can surely provide them.

Thanks,
Alkis