LFS 8.3 Glibc-2.28 make check fail 'stdlib/test-bz22786' - glibc

Question

I am on Section 6.9 of the LFS book, My host OS is Ubuntu 18.04, When I ran make check I got errors as follow:
UNSUPPORTED: elf/tst-audit10
UNSUPPORTED: elf/tst-avx512
XPASS: elf/tst-protected1a
XPASS: elf/tst-protected1b
FAIL: inet/tst-idna_name_classify
UNSUPPORTED: math/test-double-libmvec-alias-avx512
UNSUPPORTED: math/test-double-libmvec-alias-avx512-main
UNSUPPORTED: math/test-double-libmvec-sincos-avx512
UNSUPPORTED: math/test-float-libmvec-alias-avx512
UNSUPPORTED: math/test-float-libmvec-alias-avx512-main
UNSUPPORTED: math/test-float-libmvec-sincosf-avx512
UNSUPPORTED: misc/tst-pkey
FAIL: misc/tst-ttyname
UNSUPPORTED: nptl/test-cond-printers
UNSUPPORTED: nptl/test-condattr-printers
UNSUPPORTED: nptl/test-mutex-printers
UNSUPPORTED: nptl/test-mutexattr-printers
UNSUPPORTED: nptl/test-rwlock-printers
UNSUPPORTED: nptl/test-rwlockattr-printers
UNSUPPORTED: posix/tst-sysconf-empty-chroot
UNSUPPORTED: resolv/tst-resolv-ai_idn
UNSUPPORTED: resolv/tst-resolv-ai_idn-latin1
FAIL: stdlib/test-bz22786
Summary of test results:
3 FAIL
5836 PASS
18 UNSUPPORTED
17 XFAIL
2 XPASS
make[1]: *** [Makefile:347: tests] Error 1
make[1]: Leaving directory '/sources/glibc-2.28'
make: *** [Makefile:9: check] Error 2
I want know the error stdlib/test-bz22786 is a harmless message or not?

Answer 1

The old version of stdlib/test-bz22786 needed more than 2 GiB of RAM to complete successfully. If your system does not have that much RAM and uses swap space instead, the test will execute very slowly and eventually time out, leading to the test failure you see.
This is fixed on the release/2.28/master upstream branch, by backporting this upstream commit which uses alias mappings for memory compression. The backport needs some further patches, which are also on the branch. It's usually a good idea to track the release branch (except that a commit broke malloc earlier this week, so perhaps now is not a good time to start).
Thanks for paying attention to glibc test results.