Re: [Libguestfs] More parallelism in VDDK driver (was: Re: CFME-5.11.7.3 Perf. Tests)

On Wed, Aug 5, 2020 at 3:47 PM Richard W.M. Jones <rjones(a)redhat.com&gt; wrote: > > > Here are some results anyway. The command I'm using is: > > $ ./nbdkit -r -U - vddk \ > libdir=/path/to/vmware-vix-disklib-distrib \ > user=root password='***' \ > server='***' thumbprint=aa:bb:cc:... \ > vm=moref=3 \ > file='[datastore1] Fedora 28/Fedora 28.vmdk' \ > --run 'time /var/tmp/threaded-reads $unixsocket' > > Source for threaded-reads is attached. > > (1) Existing nbdkit VDDK plugin. > > NR_MULTI_CONN = 1 > NR_CYCLES = 10000 > > Note this is making 10,000 pread requests. > > real 1m26.103s > user 0m0.283s > sys 0m0.571s > > (2) VDDK plugin patched to support SERIALIZE_REQUESTS. > > NR_MULTI_CONN = 1 > NR_CYCLES = 10000 > > Note this is making 10,000 pread requests. > > real 1m26.755s > user 0m0.230s > sys 0m0.539s > > (3) VDDK plugin same as in (2). > > NR_MULTI_CONN = 8 > NR_CYCLES = 10000 > > Note this is making 80,000 pread requests in total. > > real 7m11.729s > user 0m2.891s > sys 0m6.037s > > My observations: > > Tests (1) and (2) are about the same within noise. > > Test (3) is making 8 times as many requests as test (1), so I think > it's fair to compare the 8 x time taken by test (1) (ie. the time it > would have taking to make 80,000 requests): > > Test (1) * 8 = 11m28 > Test (3) = 7m11 That's pretty good results, 62% faster. What is the request size used? I would test 1, 2, 4, 8 MiB reads.

> So if we had a client which could actually use multi-conn then this > would be a reasonable win. It seems like there's still a lot of > locking going on somewhere, perhaps inside VDDK or in the server. > It's certainly nowhere near a linear speedup. > > The patch does at least seem stable. I'll post it in a minute. > > Rich. > > -- > Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones > Read my programming and virtualization blog: http://rwmj.wordpress.com > libguestfs lets you edit virtual machines. Supports shell scripting, > bindings from many languages. http://libguestfs.org