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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>
Message-ID: <5601db40-ee2f-262d-7d01-5c589c9a07eb@gmail.com>
Date:   Thu, 19 Sep 2019 23:20:39 +0300
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On 9/19/19 11:05 PM, Trond Myklebust wrote:
> There are plenty of operations that can take longer than 700 ms to
> complete. Synchronous writes to disk are one, but COMMIT (i.e. the NFS
> equivalent of fsync()) can often take much longer even though it has no
> payload.
> 
> So the problem is not the size of the WRITE payload. The real problem
> is the timeout.
> 
> The bottom line is that if you want to keep timeo=7 as a mount option
> for TCP, then you are on your own.
> 

The problem isn't timeo at all.
If I understand it correctly, when I try to launch firefox over nfsroot, 
NFS will wait until it fills 1M before "replying" to the application.
Thus the applications will launch a lot slower, as they get "disk 
feedback" in larger chunks and not "snappy".

In numbers:
timeo=600,rsize=1M => firefox opens in 30 secs
timeo=600,rsize=32k => firefox opens in 20 secs

Anyway, thank you very much for your time and feedback.

Kind regards,
Alkis Georgopoulos