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

Anna Schumaker
2015-03-27T19:04:50Z

I did two separate dd tests with the same 5G file from yesterday, and still using the same virtual machines. First, I ran dd using direct IO for reads:
dd if=/nfs/file iflag=direct of=/dev/null bs=128K

Mixed file performance was awful, so I reran without direct IO enabled for comparison:
dd if=/nfs/file iflag=nocache of=/dev/null oflag=nocache bs=128K

bs=128K sets the block size used by dd to the NFS rsize, without this dd will only read 512 bytes at a time and take forever to complete.

##########################
# #
# Without READ_PLUS #
# #
##########################

NFS v4.1, iflag=direct:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 11.704s | 11.055s | 11.329s | 11.453s | 10.741s | 11.256s |
| Hole | 9.839s | 9.326s | 9.381s | 9.430s | 8.875s | 9.370s |
| Mixed | 19.150s | 19.468s | 18.650s | 18.537s | 19.312s | 19.023s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2, iflag=direct:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 10.927s | 10.885s | 11.114s | 11.283s | 10.371s | 10.916s |
| Hole | 9.515s | 9.039s | 9.116s | 8.867s | 8.905s | 9.088s |
| Mixed | 19.149s | 18.656s | 19.400s | 18.834s | 20.041s | 19.216s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.1, iflag=nocache oflag=nocache:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 6.808s | 6.698s | 7.482s | 6.761s | 7.235s | 6.995s |
| Hole | 5.350s | 5.148s | 5.161s | 5.070s | 5.089s | 5.164s |
| Mixed | 9.316s | 8.731s | 9.072s | 9.145s | 8.627s | 8.978s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2, iflag=nocache oflag=nocache:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 6.686s | 6.848s | 6.876s | 6.799s | 7.815s | 7.004s |
| Hole | 5.092s | 5.330s | 5.050s | 5.280s | 5.030s | 5.156s |
| Mixed | 8.142s | 7.897s | 8.040s | 7.960s | 8.050s | 8.018s |
|---------|---------|---------|---------|---------|---------|---------|

#######################
# #
# With READ_PLUS #
# #
#######################

NFS v4.1, iflag=direct:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 9.464s | 10.181s | 10.048s | 9.452s | 10.795s | 9.988s |
| Hole | 7.954s | 8.486s | 7.762s | 7.969s | 8.299s | 8.094s |
| Mixed | 19.037s | 18.323s | 18.965s | 18.156s | 19.185s | 18.733s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2, iflag=direct:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 11.923s | 10.026s | 10.222s | 12.387s | 11.431s | 11.198s |
| Hole | 3.247s | 3.155s | 3.191s | 3.243s | 3.202s | 3.208s |
| Mixed | 54.677s | 54.697s | 52.978s | 53.704s | 54.054s | 54.022s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.1, iflag=nocache oflag=nocache:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 6.788s | 6.802s | 6.750s | 6.756s | 6.852s | 6.790s |
| Hole | 5.143s | 5.165s | 5.104s | 5.154s | 5.116s | 5.136s |
| Mixed | 7.902s | 7.693s | 9.169s | 8.186s | 9.157s | 8.421s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2, iflag=nocache oflag=nocache:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 6.897s | 6.862s | 7.054s | 6.961s | 7.081s | 6.971s |
| Hole | 1.690s | 1.673s | 1.553s | 1.554s | 1.490s | 1.592s |
| Mixed | 9.009s | 7.840s | 7.661s | 8.945s | 7.649s | 8.221s |
|---------|---------|---------|---------|---------|---------|---------|

On 03/26/2015 12:13 PM, Trond Myklebust wrote:
> 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.