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

[Trond Myklebust]

On Thu, Mar 26, 2015 at 12:11 PM, Anna Schumaker
<Anna.Schumaker at 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 at 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 at 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 at primarydata.com