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[81.186.20.0]) by smtp.googlemail.com with ESMTPSA id g185sm8763909wme.10.2019.09.21.04.02.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 21 Sep 2019 04:02:44 -0700 (PDT) Subject: Re: rsize,wsize=1M causes severe lags in 10/100 Mbps From: Alkis Georgopoulos To: "linux-nfs@vger.kernel.org" References: <3d00928cd3244697442a75b36b75cf47ef872657.camel@hammerspace.com> <7afc5770-abfa-99bb-dae9-7d11680875fd@gmail.com> <915fa536-c992-3b77-505e-829c4d049b02@gmail.com> <1d5f6643330afd2c04350006ad2a60e83aebb59d.camel@hammerspace.com> <5601db40-ee2f-262d-7d01-5c589c9a07eb@gmail.com> <20190919211912.GA21865@cosmos.ssec.wisc.edu> <503c22ad34b3f3a15015b7384bcad469b2899cb4.camel@hammerspace.com> <20190919221601.GA30751@cosmos.ssec.wisc.edu> <0213704b-3930-5be6-bd3d-dbaabc24a270@gmail.com> <1e7c9896-eb1b-9d7c-fff0-6df2b3d96392@gmail.com> <6fa596e9-b154-310e-9685-7663731618ba@gmail.com> <675724ca-bdb4-324b-b3ec-2fba608b8358@gmail.com> Message-ID: <0b76213e-426b-0654-5b69-02bfead78031@gmail.com> Date: Sat, 21 Sep 2019 14:02:43 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <675724ca-bdb4-324b-b3ec-2fba608b8358@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org 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