[klibc] nfsmount default timeo=7 causes timeouts on 100 Mbps

[Ben Hutchings]

On Sat, 2019-09-21 at 14:14 +0300, Alkis Georgopoulos wrote:
> I managed to get to the bottom of this, and filed a bug report for NFS:
> https://bugzilla.kernel.org/show_bug.cgi?id=204939
> 
> Klibc nfsmount still a bug: it needs to NOT hardcode timeo=7.

Right.  It looks like we should set it to 0 and the kernel will then
substitute its default value.  This is what nfs-utils appears to do.

Ben.

> Either the NFS defaults should be used,
> which result in: timeo=600,rsize=1048576,wsize=1048576,
> or at least the kernel documented defaults,
> https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt
> which are: timeo=7,rsize=4096,wsize=4096
> 
> But clearly hardcoding (the old) timeo=7 and leaving the (new) default 
> rsize=1048576 is wrong and it's causing dmesg errors.
> 
> With all the workarounds applied, the traffic for netbooting a client 
> with ext4-over-nfs dropped from e.g. 1160 MB to 221 MB, i.e. it's a 
> major improvement.

-- 
Ben Hutchings
Nothing is ever a complete failure;
it can always serve as a bad example.


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