[PATCH v2] fs: nfs: Start earlier to resend requests

[Gavin Schenk]

On Fri, Jun 11, 2021 at 09:13:51AM +0200, Uwe Kleine-König wrote:
> On a customer site we're experience a bit over 1% UDP packet loss. When
> wiresharking an NFS transfer of a kernel image (with the goal to boot
> via NFS) I saw 64 of 2555 RPC calls staying unanswered. With the current
> timeout setting each of them introduces a delay of 2 seconds and the
> whole transfer takes 137s. With the timeout reduced to 0.1s the transfer
> time is not optimal (going down to approx 15 seconds) but at least it
> becomes bearable.
> 
> To still cope with a slow network (in contrast to an unreliable as
> pictured above) increase NFS_MAX_RESEND to keep NFS_TIMEOUT *
> NFS_MAX_RESEND (which defines the overall timeout before aborting the
> transfer) constant.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
Acked-by: Gavin Schenk <g.schenk at eckelmann.de>

I have tested this on the customer site with 1% UDP loss :). I am working with
the IT department to get a better network. Until that happens, this patch helps
me successfully boot NFS.

Regards
Gavin Schenk