[LTP] [Query] With THP numa01 - test5() fails

[Cyril Hrubis]

Hi!
> While running LTP test suite with 4.18 kernel ( arm64 ).
> I see the below failure with THP (Transparent Hugepages) enabled.
> test5 -  Verification of shared memory interleaved on all nodes
> 
> numa01 1 TINFO: The system contains 2 nodes: 0 1 
> numa01 1 TPASS: NUMA local node and memory affinity
> numa01 2 TPASS: NUMA preferred node policy
> numa01 3 TPASS: NUMA share memory allocated in preferred node
> numa01 4 TPASS: NUMA interleave policy
> numa01 5 TFAIL: NUMA interleave share memory allocated in node1 is less than expected

There are some problems with the test5. It also fails frequenty if /tmp
is on btrfs, the problem here is that file based mappings that are
(faulted) allocated by the filesystem driver do not tend to be
distributed fully evenly for various reasons (e.g. metadata blocks are
allocated in batches on btrfs).

So my guess here would be that THP causes some part(s) of the file, be
it metadata or the actuall data, backed up by a transparent huge page,
which causes the pages to be distributed unevely.

The solution is to take more than one sample and see if data are
distributed more or less evenly over sum of the samples, which is what
I'm working on in replacement for this test that would fix this problem
along with a few more, see:

http://lists.linux.it/pipermail/ltp/2018-August/009109.html

Can try the tests from that patchset to see if these are working fine
for you?

-- 
Cyril Hrubis
chrubis@suse.cz