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From: Alkis Georgopoulos <alkisg@gmail.com>
To: "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: rsize,wsize=1M causes severe lags in 10/100 Mbps
Date: Sat, 21 Sep 2019 14:02:43 +0300
Message-ID: <0b76213e-426b-0654-5b69-02bfead78031@gmail.com> (raw)
In-Reply-To: <675724ca-bdb4-324b-b3ec-2fba608b8358@gmail.com>

On 9/21/19 10:59 AM, Alkis Georgopoulos wrote:
> I.e. the problem probably is that when NFS_MAX_READAHEAD=15 was 
> implemented, rsize was 512k; now that rsize=1M, this results in 
> readaheads of 15M, which cause all the traffic and lags.


I filed a bug report for this:
https://bugzilla.kernel.org/show_bug.cgi?id=204939

A quick work around is to run on the clients, after the NFS mounts:

for f in $(awk '/^v[0-9]/ { print $4 }' < /proc/fs/nfsfs/volumes); do
     echo 4 > /sys/devices/virtual/bdi/$f/read_ahead_kb
done

Btw the mail title is wrong, the workaround above causes the netboot
traffic to drop from e.g. 1160MB to 221MB in any network speed;
it was just more observable in lower speeds.

Thank you very much,
Alkis Georgopoulos

      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
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 [this message]

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