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

[J. Bruce Fields]

On Wed, Apr 15, 2015 at 03:32:02PM -0400, Anna Schumaker wrote:
> 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:

Have you tried the implementation we discussed that always returns a
single segment covering the whole requested range, by treating holes as
data if necessary when they don't cover the whole range?

(Also: I assume it's the same as before, but: when you post test
results, could you repost if necessary:

	- what the actual test is
	- what the hardware/software setup is on client and server

so that we have reproduceable results for posterity's sake.)

Interesting that "Mixed" is a little slower even before READ_PLUS.

And I guess we should really report this to ext4 people, looks like they
may have a bug.

--b.

> 
> ###########
> #         #
> #   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 |
> |---------|---------|---------|---------|---------|---------|---------|