[Libguestfs] [PATCH nbdkit NOT WORKING 0/2] vddk: Relax threading model.

[Richard W.M. Jones]

Even running this with lots of extra debugging it seems to be doing
what is expected.  I can't see the bug if there is one.

Note I'm only testing qemu-img convert as that is what's relevant to
virt-v2v.  Previously I was using a hand-written test using libnbd
that did random reads across the disk, and showed a modest improvement
with 8 handles.

Here are the results across a range of pool sizes, all with -W -m 16:

1 handle:
real	1m8.031s
user	0m0.112s
sys	0m1.560s

2 handles:
real	1m6.465s
user	0m0.106s
sys	0m1.607s

4 handles:
real	1m21.488s
user	0m0.126s
sys	0m1.620s

8 handles:
real	1m27.790s
user	0m0.099s
sys	0m1.625s

16 handles:
real	1m33.974s
user	0m0.124s
sys	0m1.718s

I also tried matching the number of coroutines to the number
of handles in the pool (ie pool-max == -m):

1 coroutine, 1 handle:
real	     1m9.545s
user	     0m0.083s
sys	     0m1.592s

2 coroutines, 2 handles:
real	      1m6.130s
user	      0m0.078s
sys	      0m1.567s

4 coroutines, 4 handles:
real	      1m22.109s
user	      0m0.107s
sys	      0m1.690s

8 coroutines, 8 handles:
real	      1m26.490s
user	      0m0.108s
sys	      0m1.650s

16 coroutines, 16 handles (same as last result above):
real	1m33.974s
user	0m0.124s
sys	0m1.718s


Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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