Re: [PATCH v3 3/3] NFSD: Add support for encoding multiple segments

Trond Myklebust
2015-03-26T16:13:32Z

On Thu, Mar 26, 2015 at 12:11 PM, Anna Schumaker
<Anna.Schumaker@netapp.com> wrote:
> On 03/26/2015 12:06 PM, Trond Myklebust wrote:
>> On Thu, Mar 26, 2015 at 11:47 AM, Anna Schumaker
>> <Anna.Schumaker@netapp.com> wrote:
>>> On 03/26/2015 11:38 AM, J. Bruce Fields wrote:
>>>> On Thu, Mar 26, 2015 at 11:32:25AM -0400, Trond Myklebust wrote:
>>>>> On Thu, Mar 26, 2015 at 11:21 AM, Anna Schumaker
>>>>> <Anna.Schumaker@netapp.com> wrote:
>>>>>> Here are my updated numbers! I tested with files 5G in size: one 100% data, one 100% hole, and one alternating between hole and data every 4K. I collected data for both v4.1 and v4.2 with and without the READ_PLUS patches:
>>>>>>
>>>>>> ##########################
>>>>>> # #
>>>>>> # Without READ_PLUS #
>>>>>> # #
>>>>>> ##########################
>>>>>>
>>>>>>
>>>>>> NFS v4.1:
>>>>>> Trial
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>> | | 1 | 2 | 3 | 4 | 5 | Average |
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>> | Data | 8.723s | 7.243s | 8.252s | 6.997s | 6.980s | 7.639s |
>>>>>> | Hole | 5.271s | 5.224s | 5.060s | 4.897s | 5.321s | 5.155s |
>>>>>> | Mixed | 8.050s | 10.057s | 7.919s | 8.060s | 9.557s | 8.729s |
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> NFS v4.2:
>>>>>> Trial
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>> | | 1 | 2 | 3 | 4 | 5 | Average |
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>> | Data | 6.707s | 7.070s | 6.722s | 6.761s | 6.810s | 6.814s |
>>>>>> | Hole | 5.152s | 5.149s | 5.213s | 5.206s | 5.312s | 5.206s |
>>>>>> | Mixed | 7.979s | 7.985s | 8.177s | 7.772s | 8.280s | 8.039s |
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> #######################
>>>>>> # #
>>>>>> # With READ_PLUS #
>>>>>> # #
>>>>>> #######################
>>>>>>
>>>>>>
>>>>>> NFS v4.1:
>>>>>> Trial
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>> | | 1 | 2 | 3 | 4 | 5 | Average |
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>> | Data | 9.082s | 7.008s | 7.116s | 6.771s | 7.902s | 7.576s |
>>>>>> | Hole | 5.333s | 5.358s | 5.380s | 5.161s | 5.282s | 5.303s |
>>>>>> | Mixed | 8.189s | 8.308s | 9.540s | 7.937s | 8.420s | 8.479s |
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> NFS v4.2:
>>>>>> Trial
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>> | | 1 | 2 | 3 | 4 | 5 | Average |
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>> | Data | 7.033s | 6.829s | 7.025s | 6.873s | 7.134s | 6.979s |
>>>>>> | Hole | 1.794s | 1.800s | 1.905s | 1.811s | 1.725s | 1.807s |
>>>>>> | Mixed | 7.590s | 8.777s | 9.423s | 10.366s | 8.024s | 8.836s |
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>>
>>>>>
>>>>> So there is a clear win in the 100% hole case here, but otherwise the
>>>>> statistical fluctuations are dominating the numbers. Can you get us a
>>>>> little more stats and then perhaps run the results through nfsometer?
>>>>
>>>> Also, could you describe the setup (are these still kvm's), and how
>>>> you're clearing the cache between runs?
>>>
>>> These are still KVMs and my server is exporting an xfs filesystem. I clear caches by running "echo 3 > /proc/sys/vm/drop_caches" on the server before every read, and I remount my client after reading each set of three files once.
>>
>> I agree that you have to use the 'drop_caches' interface on the
>> server, but why not just use O_DIRECT on the clients?
>
> I've been reading by using cat from my test shell script: `time cat /nfs/file > /dev/null`. I can write something to read files with O_DIRECT if that would be more useful!
>

'dd' can do that for you if the appropriate incantations are performed.

--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com