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

To: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
Subject: Re: [PATCH v3 3/3] NFSD: Add support for encoding multiple segments
From: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Date: Fri, 27 Mar 2015 17:08:39 -0400
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Marc Eshel <eshel@xxxxxxxxxx>, "linux-nfs@xxxxxxxxxxxxxxx" <linux-nfs@xxxxxxxxxxxxxxx>, linux-nfs-owner@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <5515C3BE.3040807@xxxxxxxxxx>
References: <20150326153848.GB30482@xxxxxxxxxxxx> <551429F7.5050305@xxxxxxxxxx> <CAHQdGtRCrrhdS8F4FjZFT-CnRRGm8eZR07v8WnK7bwagKgmPcw@xxxxxxxxxxxxxx> <55142FB4.2070408@xxxxxxxxxx> <CAHQdGtS_VuBOzRZjsiYdjZS8qMj2Sw65BYdFmWWf-LJhQL6yOg@xxxxxxxxxxxxxx> <5515A9C8.6090400@xxxxxxxxxx> <CAHQdGtRaUYxU2JAAWErH7FT=Gy5JLzAKi-RtqqBSkNFZrhaB9Q@xxxxxxxxxxxxxx> <5515C1BF.8000907@xxxxxxxxxx> <20150327205414.GD27889@xxxxxxxxxxxx> <5515C3BE.3040807@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
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@xxxxxxxxxx> 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@xxxxxxxxxx> wrote:
> >>>>>> On 03/26/2015 12:06 PM, Trond Myklebust wrote:
> >>>>>>> On Thu, Mar 26, 2015 at 11:47 AM, Anna Schumaker
> >>>>>>> <Anna.Schumaker@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx
> >>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>>
> >>>
> >>>

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