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From:   Trond Myklebust <trondmy@gmail.com>
Date:   Thu, 19 Sep 2019 11:08:46 -0400
Message-ID: <CAABAsM7XHjTC4311-XY04RSy_XJs+E+j+-3prYAarX_=k0259g@mail.gmail.com>
Subject: Re: rsize,wsize=1M causes severe lags in 10/100 Mbps, what sets those defaults?
To:     Alkis Georgopoulos <alkisg@gmail.com>
Cc:     linux-nfs@vger.kernel.org
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On Thu, 19 Sep 2019 at 03:44, Alkis Georgopoulos <alkisg@gmail.com> wrote:
>
> Hi, in any recent distribution that I tried, the default NFS wsize/rsize
> was 1 MB.
>
> On 10/100 Mbps networks, this causes severe lags, timeouts, and dmesg
> fills with messages like:
>
>  > [  316.404250] nfs: server 192.168.1.112 not responding, still trying
>  > [  316.759512] nfs: server 192.168.1.112 OK
>
> Forcing wsize/rsize to 32K makes all the problems disappear and NFS
> access more snappy, without sacrificing any speed at least up to gigabit
> networks that I tested with.
>
> I would like to request that the defaults be changed to 32K.
> But I didn't find out where these defaults come from, where to file the
> issue and my test case / benchmarks to support it.
>
> I've initially reported it at the klibc nfsmount program that I was
> using, but this is just using the NFS defaults, which are the ones that
> should be amended. So initial test case / benchmarks there:
> https://lists.zytor.com/archives/klibc/2019-September/004234.html
>
> Please Cc me as I'm not in the list.
>

The default client behaviour is just to go with whatever recommended
value the server specifies. You can change that value yourself on the
knfsd server by editing the pseudo-file in
/proc/fs/nfsd/max_block_size.

Cheers
   Trond