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From: Trond Myklebust <trondmy@hammerspace.com>
To: "alkisg@gmail.com" <alkisg@gmail.com>,
	"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: rsize,wsize=1M causes severe lags in 10/100 Mbps
Date: Thu, 19 Sep 2019 16:11:00 +0000
Message-ID: <3d00928cd3244697442a75b36b75cf47ef872657.camel@hammerspace.com> (raw)
In-Reply-To: <ee758eaf-c02d-f669-bc31-f30e6b17d92a@gmail.com>

On Thu, 2019-09-19 at 18:58 +0300, Alkis Georgopoulos wrote:
> On 9/19/19 6:08 PM, Trond Myklebust wrote:
> > 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.
> 
> Thank you, and I guess I can automate this, by running
> `systemctl edit nfs-kernel-server`, and adding:
> [Service]
> ExecStartPre=sh -c 'echo 32768 > /proc/fs/nfsd/max_block_size'
> 
> But isn't it a problem that the defaults cause errors in dmesg and 
> severe lags in 10/100 Mbps, and even make 1000 Mbps a lot less
> snappy 
> than with 32K?
> 

No. It is not a problem, because nfs-utils defaults to using TCP
mounts. Fragmentation is only a problem with UDP, and we stopped
defaulting to that almost 2 decades ago.

However it may well be that klibc is still defaulting to using UDP, in
which case it should be fixed. There are major Linux distros out there
today that don't even compile in support for NFS over UDP any more.

Cheers
  Trond
-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com



  reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-19  7:29 rsize,wsize=1M causes severe lags in 10/100 Mbps, what sets those defaults? Alkis Georgopoulos
2019-09-19 15:08 ` Trond Myklebust
2019-09-19 15:58   ` rsize,wsize=1M causes severe lags in 10/100 Mbps Alkis Georgopoulos
2019-09-19 16:11     ` Trond Myklebust [this message]
2019-09-19 19:21       ` Alkis Georgopoulos
2019-09-19 19:51         ` Trond Myklebust
2019-09-19 19:57           ` Alkis Georgopoulos
2019-09-19 20:05             ` Trond Myklebust
2019-09-19 20:20               ` Alkis Georgopoulos
2019-09-19 20:40                 ` Trond Myklebust
2019-09-19 21:19                   ` Daniel Forrest
2019-09-19 21:42                     ` Trond Myklebust
2019-09-19 22:16                       ` Daniel Forrest
2019-09-20  9:25                         ` Alkis Georgopoulos
2019-09-20  9:48                           ` Alkis Georgopoulos
2019-09-20 10:04                             ` Alkis Georgopoulos
2019-09-21  7:52                               ` Alkis Georgopoulos
2019-09-21  7:59                                 ` Alkis Georgopoulos
2019-09-21 11:02                                   ` Alkis Georgopoulos

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