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Date: Thu, 30 Jun 2011 18:13:08 +0300
From: Benny Halevy <bhalevy@panasas.com>
To: Trond Myklebust <Trond.Myklebust@netapp.com>
CC: Andy Adamson <andros@netapp.com>, quanli gui <gqlxj1987@gmail.com>,
        Benny Halevy <bhalevy@tonian.com>, linux-nfs@vger.kernel.org,
        "Mueller, Brian" <bmueller@panasas.com>
Subject: Re: [nfsv4]nfs client bug
References: <BANLkTi=xcQseTx8BTWEzg-1DO=ayJuMLrw@mail.gmail.com>	 <4E0B52BB.8090003@tonian.com>	 <BANLkTinxF+obzedP+xupMCDZcgRTFDsQMg@mail.gmail.com>	 <4CC6F947-FE93-47E4-9FD9-C0EB4D8033A6@netapp.com> <1309443867.9544.59.camel@lade.trondhjem.org>
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On 2011-06-30 17:24, Trond Myklebust wrote:
> On Thu, 2011-06-30 at 09:36 -0400, Andy Adamson wrote: 
>> On Jun 29, 2011, at 10:32 PM, quanli gui wrote:
>>
>>> When I use the iperf tools for one client to 4 ds, the network
>>> throughput is 890MB/S. It reflect that it is indeed 10GE non-blocking.
>>>
>>> a. about block size, I use bs=1M when I use dd
>>> b. we indeed use the tcp (doesn't the nfsv4 use the tcp defaultly?)
>>> c. the jumbo frames is what? how set mtu automatically?
>>>
>>> Brian, do you have some more tips?
>>
>> 1) Set the mtu on both the client and the server 10G interface. Sometimes 9000 is too high. My setup uses 8000.
>> To set MTU on interface eth0.
>>
>> % ifconfig eth0 mtu 9000
>>
>> iperf will report the MTU of the full path between client and server - use it to verify the MTU of the connection.
>>
>> 2) Increase the # of rpc_slots on the client.
>> % echo 128 > /proc/sys/sunrpc/tcp_slot_table_entries
>>
>> 3) Increase the # of server threads
>>
>> % echo 128 > /proc/fs/nfsd/threads
>> % service nfs restart
>>
>> 4) Ensure the TCP buffers on both the client and the server are large enough for the TCP window.
>> Calculate the required buffer size by pinging the server from the client with the MTU packet size and multiply the round trip time by the interface capacity
>>
>> % ping -s 9000 server  - say 108 ms average
>>
>> 10Gbits/sec = 1,250,000,000 Bytes/sec * .108 sec = 135,000,000 bytes
>>
>> Use this number to set the following: 
>> sysctl -w net.core.rmem_max = 135000000
>> sysctl -w net.core.wmem_max 135000000
>> sysctl -w "net.ipv4.tcp_rmem <first number unchaged> <second unchanged> 135000000"
>> sysctl net.ipv4.tcp_wmem  <first number unchaged> <second unchanged> 135000000"
>>
>> 5) mount with rsize=131072,wsize=131072
> 
> 6) Note that NFS always guarantees that the file is _on_disk_ after
> close(), so if you are using 'dd' to test, then you should be using the
> 'conv=fsync' flag (i.e 'dd if=/dev/zero of=test count=20k conv=fsync')
> in order to obtain a fair comparison between the NFS and local disk
> performance. Otherwise, you are comparing NFS and local _pagecache_
> performance.

FWIW, modern versions of gnu dd (not sure exactly which version changed that)
calculate and report throughput after close()ing the output file.

Benny

> 
> Trond