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

Anna Schumaker
2015-04-15T19:32:13Z

I just ran some more tests comparing the directio case across different filesystem types. These tests used three 1G files: 100% data, 100% hole, and mixed file with alternating 4k data and hole segments. The mixed case seems to be consistently slower compared to NFS v4.1, and I'm at a loss for anything I could do to make it faster. Here are my numbers:

###########
# #
# XFS #
# #
###########

NFS v4.1:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 1.883s | 1.808s | 1.781s | 1.685s | 1.591s | 1.746s |
| Hole | 1.815s | 1.635s | 1.682s | 1.698s | 1.653s | 1.697s |
| Mixed | 2.089s | 2.024s | 1.970s | 1.925s | 2.049s | 2.011s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 1.849s | 1.879s | 1.852s | 1.799s | 1.781s | 1.832s |
| Hole | 0.668s | 0.600s | 0.611s | 0.619s | 0.617s | 0.623s |
| Mixed | 5.913s | 5.811s | 5.952s | 5.962s | 5.806s | 5.889s |
|---------|---------|---------|---------|---------|---------|---------|

############
# #
# EXT4 #
# #
############

NFS v4.1:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 2.637s | 1.823s | 1.792s | 1.816s | 2.000s | 2.014s |
| Hole | 1.734s | 1.743s | 1.709s | 1.761s | 1.871s | 1.764s |
| Mixed | 5.465s | 2.158s | 2.254s | 2.676s | 2.422s | 2.995s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 1.934s | 1.783s | 1.800s | 2.010s | 1.982s | 1.902s |
| Hole | 63.568s | 63.423s | 64.671s | 66.190s | 65.985s | 64.767s |
| Mixed | 6.010s | 5.798s | 6.146s | 6.460s | 6.720s | 6.225s |
|---------|---------|---------|---------|---------|---------|---------|

#############
# #
# BTRFS #
# #
#############

NFS v4.1:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 2.386s | 1.952s | 1.832s | 1.818s | 1.826s | 1.963s |
| Hole | 1.759s | 1.717s | 1.754s | 1.621s | 1.708s | 1.712s |
| Mixed | 2.889s | 2.272s | 2.778s | 2.277s | 2.255s | 2.494s |
|---------|---------|---------|---------|---------|---------|---------|

NFS v4.2:
Trial
|---------|---------|---------|---------|---------|---------|---------|
| | 1 | 2 | 3 | 4 | 5 | Average |
|---------|---------|---------|---------|---------|---------|---------|
| Data | 2.586s | 1.816s | 2.022s | 1.862s | 1.975s | 2.052s |
| Hole | 0.646s | 0.659s | 0.669s | 0.628s | 0.605s | 0.641s |
| Mixed | 8.555s | 8.553s | 7.904s | 8.567s | 8.286s | 8.373s |
|---------|---------|---------|---------|---------|---------|---------|

On 03/27/2015 05:08 PM, J. Bruce Fields wrote:
> On Fri, Mar 27, 2015 at 04:55:26PM -0400, Anna Schumaker wrote:
>> On 03/27/2015 04:54 PM, J. Bruce Fields wrote:
>>> On Fri, Mar 27, 2015 at 04:46:55PM -0400, Anna Schumaker wrote:
>>>> On 03/27/2015 04:22 PM, Trond Myklebust wrote:
>>>>> On Fri, Mar 27, 2015 at 3:04 PM, Anna Schumaker
>>>>> <Anna.Schumaker@netapp.com> wrote:
>>>>>> 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 |
>>>>>
>>>>> That's a bit nasty. Any idea what is going on with the Mixed case here?
>>>>
>>>> Not offhand, but my first guess would be something to do with extra seeks to find how long each hole and data segment is.
>>>
>>> Remind us what "mixed" means? (I think you were alternating, but how
>>> large is each segment?)
>>
>> "Mixed" is alternating 4K segments.
>
> So it's probably doing 128/4 = 32 reads where previously one was
> necessary. You could confirm that by looking at the READ counts in
> /proc/self/mountstats. With odirect turned off maybe that's hidden by
> readahead?
>
> --b.
>
>>
>>>
>>> --b.
>>>
>>>>
>>>> Anna
>>>>
>>>>>
>>>>>> |---------|---------|---------|---------|---------|---------|---------|
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> 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.
>>>>>>>
>>>>>>
>>>>>> --
>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
>>>>>> the body of a message to majordomo@vger.kernel.org
>>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>>>>
>>>>>
>>>>>