On Nov 21, 2016, at 2:37 PM, John Bent <John.Bent(a)seagategov.com> wrote:
Thanks Sarp! Some comments in-line.
> On Nov 21, 2016, at 2:22 PM, Oral, H. Sarp <oralhs(a)ornl.gov> wrote:
>
> Well, I agree with John that trying to define a new and all around benchmark is
highly difficult. We tried that (and looked a few other benchmarks at the time) and
failed. No need to repeat the same mistakes, I think.
>
> And I also agree that the benchmarks need to be simple and easy to run and
representative of realistic scenarios.
>
> Rather than limiting to two IOR instances, we can perhaps increase them slightly to
cover more I/O workloads with IOR, if needed.
>
> By the way, we already have an IOR version that we integrated with ADIOS. We can
share it with the community. And IOR already supports HDF5, and MPIIO. Between POSIX and
these mid level libs, I think IOR covers a majority of the use cases. The trick is coming
up with good, canned command line option sets for IOR covering various I/O workloads.
>
> There is really nothing else on measuring the mdtest today as far as I know.
In terms of mdtest, when I speak of it, I have to admit that I’m speaking of a
theoretical future mdtest which does not yet exist. IOR is beautifully engineered with a
fantastic plug-in feature as you mention. The mdtest I’m envisioning is taking mdtest.c
from it’s current github and moving it into the IOR github and rewriting it to replace the
POSIX calls into calls to this IOR plug-in interface. The plug-in interface is already
almost a superset of what mdtest needs. I think only ‘stat’ needs to be added. That way,
when people add new plug-ins to IOR, they will simultaneously add them to mdtest. Also,
for our benchmark, they’d simply pull and ‘make’ from a single repository.
I would agree - it makes the most sense to improve a well-established benchmark like
mdtest to allow non-POSIX access methods instead of introducing Yet Another Benchmark
which will be gratuitously different in some number of ways but probably won't be
significantly better. I see that mdtest already has some abstractions for using the AWS
S3 interface, but it would be nice to avoid duplicating all the abstractions.
Any volunteers? :)
Here’s what I believe to be the most recently maintained repositories:
https://github.com/MDTEST-LANL/mdtest
https://github.com/IOR-LANL/ior
The
https://github.com/LLNL/ior site would IMHO be the canonical IOR site, based on the
number of people branching it and using it, and it is referenced from the original
https://sourceforge.net/projects/ior-sio/ page, but it has suffered from a lack of
attention recently. I've poked Chris M. there to see if he will open it up for
external contributors, otherwise the IOR-LANL site seems to be the most active.
It does appear that
https://github.com/MDTEST-LANL/mdtest is the canonical site for
mdtest, since
https://sourceforge.net/projects/mdtest/ redirects there.
Given that LANL controls both of those repos, it seems at least possible to merge these
projects?
Cheers, Andreas
I have to admit that I have not yet looked at md-real-io to do a
comparison. (sorry Julian, it is on my TODO list…)
>
> So, we are on board.
>
Fantastic. Our survey is now 1% complete. :)
Thanks,
John
>
> Thanks,
>
> Sarp
>
> --
> Sarp Oral, PhD
>
>
>
> National Center for Computational Sciences
> Oak Ridge National Laboratory
> oralhs(a)ornl.gov
> 865-574-2173
>
>
>
> On 11/20/16, 12:33 PM, "IO-500 on behalf of Julian Kunkel"
<io-500-bounces(a)vi4io.org on behalf of juliankunkel(a)googlemail.com> wrote:
>
> Dear John,
> I would definitely not go with mdtest. That one can be well optimized by read
ahead / sync. Also it is POSIX only.
> Note that for overcoming the caching problem, I wrote the md-real-io benchmark
that shares many things with mdtest.
> I would wait for the community feedback and not ignore that concepts such as ADIOS
may not necessarily fit as IOR back ends and rather to with abstract definitions first.
>
> Regards
> Julian
>
>
> Am 20.11.2016 6:12 nachm. schrieb "John Bent"
<John.Bent(a)seagategov.com>:
>
> To attempt defining the perfect IO benchmark is Quixotic. Those who dislike IO500
will always dislike IO500 regardless of what the specific benchmark is. Those who like
the idea will accept an imperfect benchmark.
>
>
> Therefore, I suggest we move forward with the straw person proposal: IOR hard, IOR
easy, mdtest hard, mdtest easy.
>
> * Average IOR hard and IOR easy. Average mdtest hard and mdtest easy.
> * Their product determines the winner.
> * Don’t report the product since it’s a meaningless unit; report the averages.
> * e.g. The winner of IO500 is TaihuLight with a score of 250 GB/s and 300K IOPs.
>
>
>
>
> Unless a proposal is strictly much better than IOR hard, IOR easy, mdtest hard,
mdtest easy, I don’t think we should consider it. The beauty of IOR hard, IOR easy,
mdtest hard, mdtest easy is that they are well-understood, well-accepted benchmarks, that
> are trivial to download and compile, and whose results are immediately
understandable. Every RFP in the world uses them. The one problem is they need a pithier
name than “IOR hard, IOR easy, mdtest hard, mdtest easy”...
>
>
> My suggestion is to poll the top 100 of the
>
top500.org <
http://top500.org> and ask them this:
>
>
> "If we were to do an IO500, and our benchmark was IOR hard, IOR easy, mdtest
hard, mdtest easy, would you participate? If not, would you participate with a different
benchmark?”
>
>
> If the bulk of the answers are “yes,” then we just figure out how to organize and
administer this thing.
> If the bulk of the answers are “no,” then we give up and do something else.
> If the bulk of the answers are “no, yes,” then we need to find a new benchmark.
>
>
> Thanks,
>
>
> John
>
>
> On Nov 20, 2016, at 7:11 AM, Julian Kunkel <juliankunkel(a)googlemail.com>
wrote:
>
> Dear all,
> based on our discussion during the BoF at SC, we could focus on the
> access pattern(s) of interest first. Later we can define which
> benchmarks (such as IOR) could implement these patterns (e.g., how to
> call existing benchmarks).
>
> This strategy gives other I/O paradigms the option to create a
> benchmark with that pattern that fits their I/O paradigm/architecture.
>
>
> Here is a draft of one that is probably not too difficult to discuss:
> Goal: IOmax: Sustained performance for well-formed I/O
>
> Rationales:
> The benchmark shall determine the best sustained I/O behavior without
> in-memory caching and I/O variability. A set of real applications that
> are highly optimized should be able to show the described access
> behavior.
>
> Use case: A large data structure is distributed across N
> threads/processes; a time series of this data structured shall be
> stored/retrieved efficiently. (This could be a checkpoint.)
>
> Processing steps:
> S0) Each thread allocates and initializes a large consecutive memory
> region of size S with a random (but well defined) pattern
> S1) Repeat T times: Each process persists/reads its data to/from the
> storage. Ech iteration is protected with a global barrier and the
> runtime is measured
> S2) Compute the throughput (as IOmax) by dividing the total accessed
> data volume (N*S) by the maximum observed runtime for any single
> iteration in step S1
>
> Rules:
> R1) The data of each thread and timestep must be stored individually
> and cannot be overwritten during a benchmark run
> R2) It must be ensured that the time includes all processes needed to
> persist all data in volatile memory (for writes) and that prior
> startup of reads no data is cached in any volatile memory
> R3) A valid result must verify that read returns the expected (random) data
> R4) N, T and S can be set arbitrarily. T must be >= 3. The benchmark
> shall be repeated several times
>
> Reported metrics:
> * IOmax
> * Working set size W: N*T*S
>
> Regards,
> Julian
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Cheers, Andreas