Re: [PATCH v2 2/4] NFSD: Add READ_PLUS support for data segments

[Anna Schumaker <Anna.Schumaker@netapp.com>]

On 02/05/2015 11:48 AM, J. Bruce Fields wrote:
> On Thu, Feb 05, 2015 at 11:43:46AM -0500, Anna Schumaker wrote:
>> On 02/05/2015 11:23 AM, Christoph Hellwig wrote:
>>> On Thu, Feb 05, 2015 at 11:06:04AM -0500, Anna Schumaker wrote:
>>>>> If the READ_PLUS implementation can't use the splice read path it's
>>>>> probably a loss for most workloads.
>>>>>
>>>>
>>>> I'll play around with the splice path, but I don't think it was designed for encoding multiple read segments.
>>>
>>> The problem is that the typical case of all data won't use splice
>>> every with your patches as the 4.2 client will always send a READ_PLUS.
>>>
>>> So we'll have to find a way to use it where it helps.  While we might be
>>> able to add some hacks to only use splice for the first segment I guess
>>> we just need to make the splice support generic enough in the long run.
>>>
>>
>> I should be able to use splice if I detect that we're only returning a single DATA segment easily enough.
> 
> Oh, good thought, yes maybe that would be enough.
> 
> But I still wish he had more evidence here.

I switched to using splice and fixed a few other bugs that happened to pop up.  xfstests definitely runs faster compared to the old code, but I haven't had a chance to compare against other NFS versions yet.

Anna

> 
> --b.
>