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

Trond Myklebust
2015-03-26T15:32:34Z

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?

>
>
> On 03/24/2015 01:49 PM, Christoph Hellwig wrote:
>> On Tue, Mar 24, 2015 at 08:43:31AM -0400, Anna Schumaker wrote:
>>>> I don't know, and don't have profiles. I'll either try to reproduce or
>>>> wait till Anna's back from vacation.
>>>
>>> I'm using whatever functions NFSD already uses for reading files,
>>> which I expect go through the VFS. Is there a flag that controls
>>> cache behavior?
>>
>> There's the O_DIRECT flag, but that's not what I mean. If you just
>> wrote to it it's a cached read, if you did unmount the filesystem after
>> writing, or did an echo to /proc/sys/vm/drop_caches you get uncached
>> read behavior.
>>
>
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--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com