Add s390x builds to Travis

[adamretter]

Highly experimental ;-)

[sangitanalkar]

Hi, any updates on the PR if the changes can be merged?

[adamretter]

@sangitanalkar No progress yet, there are a couple of issues that need to be investigated including - #6236

In addition whilst we have CI for s390x. We do not have access to an s390x system for building releases on, without that we would be unable to release binaries for that platform.

[sangitanalkar]

@adamretter we could provide the s390x system, please let us know the configuration that is needed.

[adamretter]

@sangitanalkar could you contact me directly by email to discuss.

[adamretter]

I also emailed @edelsohn about getting access to a community development system.

[edelsohn]

LinuxONE Community Cloud

[pdillinger]

This probably isn't needed now that we have pre-built binary?

[adamretter]

I will remove it

[jonathan-albrecht-ibm]

Hi @adamretter, I'd like to work on adding s390x support to rocksdb. I'm part of the same group that was asking about s390x support in #8642 but I'm just looking at the latest rocksdb.

I've starting with a rebased fork of adamretter:feature/travis-s390x and added a few fixes for recent changes. I'm down to three failing tests:

1. Full/FullBloomTest.OptimizeForMemory/0
2. DBPropertiesTest.AggregatedTableProperties
3. DBPropertiesTest.AggregatedTableProperties

and all failures seem related to bloom filters, eg:

...
[ RUN      ] Full/FullBloomTest.OptimizeForMemory/0
/home/jalbrecht/src/rocksdb/util/bloom_test.cc:555: Failure
Expected: (total_fp_rate / double{nfilters}) >= (0.008), actual: 0.007808 vs 0.008
...
[ RUN      ] DBPropertiesTest.AggregatedTableProperties                                                                     /home/jalbrecht/src/rocksdb/db/db_properties_test.cc:208: Failure                                                           Expected: (static_cast<double>(dbl_a - dbl_b) / (dbl_a + dbl_b)) < (bias), actual: 0.167604 vs 0.15  
[ RUN      ] DBPropertiesTest.AggregatedTablePropertiesAtLevel                                                              /home/jalbrecht/src/rocksdb/db/db_properties_test.cc:208: Failure
Expected: (static_cast<double>(dbl_a - dbl_b) / (dbl_a + dbl_b)) < (bias), actual: 0.518044 vs 0.5    
...

I'm not sure where to start with these. I posted this to the facebook RocksDB Developers group but didn't get a response so not sure I picked the best forum. Any suggestions on where or who to ask would be great.

I noticed all of theses tests set a seed for the random number generator so the same sequence is always used. Just a wild guess but I'm wondering if the threshold values.(0.008, 0.15, 0.5) are not really hard thresholds and if the errors might not indicate a real problem on s390x.

Thanks! Happy to provide any more info or testing as needed.

[adamretter]

@jonathan-albrecht-ibm Sorry for the delay. Would you be able to invite me again to your https://github.com/jonathan-albrecht-ibm/cmake-3.14.5-Linux-s390x-deb repository please?

[jonathan-albrecht-ibm]

@jonathan-albrecht-ibm Sorry for the delay. Would you be able to invite me again to your https://github.com/jonathan-albrecht-ibm/cmake-3.14.5-Linux-s390x-deb repository please?

np @adamretter I've resent the invite.

[adamretter]

@jonathan-albrecht-ibm Got it. Thanks :-)

[adamretter]

@jonathan-albrecht-ibm Can this now be closed in favour of your work in #8962 ?

I have one question about your PR (#8962)... Why the arch is set to z196 as opposed to z10, I have to admit that I am not clear about the numbering of the Z architecture. If I recall, I chose z10 as it was a reasonably old one that was also supported on Travis CI - so I figured it would give us the largest possible backwards/forwards compatibility.

[jonathan-albrecht-ibm]

@jonathan-albrecht-ibm Can this now be closed in favour of your work in #8962 ?

Yes, #8962 includes these changes so this can be closed.

I have one question about your PR (#8962)... Why the arch is set to z196 as opposed to z10, I have to admit that I am not clear about the numbering of the Z architecture. If I recall, I chose z10 as it was a reasonably old one that was also supported on Travis CI - so I figured it would give us the largest possible backwards/forwards compatibility.

Yes, its definitely a judgment call and I didn't mean to jump the gun on this. z196 is the next generation after z10 and z196 has been around since 2010. I had a look at what the distros support:

• z196 is the minimum supported for RHEL, Ubuntu and SLES based on: https://www.ibm.com/support/pages/linux-ibm-z-tested-platforms
• I think Stretch was the last version of Debian before z196 became the minimum: https://lists.debian.org/debian-s390/2018/02/msg00008.html

Also, I know at least golang's s390x binary dist is built for minimum z196. So my feeling is that z196 is a good default because its not likely you're going to run into a system that supports earlier than that.

[adamretter]

Thanks @jonathan-albrecht-ibm for the explanation, let's leave it as z196 for now.