Performance tweaks for powerpc64 lnt buildbots

[seurer]

Summary

1. Remove multisample option. The lnt tests are not used to test performance on power so all this option does is slow things down.
2. Use -j8 on BE powerpc64. This bot now has underused CPU available and the lnt test is the slowest one to run so increasing the parallel runs should help throughput.

[rengolin]

The multisample option is obvious, I'm not sure about the -j8. On all my LNT bots, all cores are busy all the time, so if you have 4 cores, I don't think -j8 will help you. If you have 8 cores, than you should change jobs=8, too.

[seurer]

In D13524#262182, @rengolin wrote:

The multisample option is obvious, I'm not sure about the -j8. On all my LNT bots, all cores are busy all the time, so if you have 4 cores, I don't think -j8 will help you. If you have 8 cores, than you should change jobs=8, too.

The buildbots are now the only "users" on this system and it has 64 cores though other llvm buildbots also run there. I have been monitoring it for a while now and running with -j8 should be OK. In fact, that ought to just about keep everything busy when all the bots are actively running tests.

I did some manual runs of lnt on this system yesterday and using -j8 tremendously reduced the time to run.

[seurer]

I tested the --multisample change locally on the running bots and it took 1 hour off the run time of the big endian powerpc64 lnt test bot and 3 hours off the run time of the little endian one.

[gkistanova]

LGTM.

Thanks

Galina

buildbot/osuosl/master/config/builders.py

return [
                         stage1_config='Release',
                         stage2_config='Release',
                         extra_cmake_args=["-DLLVM_ENABLE_ASSERTIONS=ON"])},
 
         {'name' : "clang-ppc64-elf-linux",
          'slavenames' :["ppc64be-clang-lnt-test"],
          'builddir' :"clang-ppc64-1",
          'factory' : LNTBuilder.getLNTFactory(triple='ppc64-elf-linux1',
-                                              nt_flags=['--multisample=3','--cflag','-mcpu=native'],
+                                              nt_flags=['--cflag','-mcpu=native', '-j8'],
                                               jobs=4,  use_pty_in_tests=True,
                                               testerName='O3-plain', run_cxx_tests=True)},
 
         {'name' : "clang-ppc64-elf-linux2",
          'slavenames' :["ppc64be-clang-multistage-test"],
          'builddir' :"clang-ppc64-2",
          'factory' : ClangBuilder.getClangBuildFactory(triple='ppc64-elf-linux',
                                                        useTwoStage=True, test=True,
                                                        checkout_compiler_rt=True,
                                                        stage1_config='Release+Asserts',
                                                        stage2_config='Release+Asserts')},
 
         {'name' : "ppc64le-clanglnt",
          'slavenames' :["ppc64le-clang-lnt-test"],
          'builddir' :"clang-lnt-ppc64le-1",
          'factory' : LNTBuilder.getLNTFactory(triple='ppc64le-elf-linux1',
-                                              nt_flags=['--multisample=3','--cflag','-mcpu=native'],
+                                              nt_flags=['--cflag','-mcpu=native'],
                                               jobs=4,  use_pty_in_tests=True,
                                               testerName='ppc64le-plain', run_cxx_tests=True)},
 
         {'name' : "ppc64le-clang",
          'slavenames' :["ppc64le-clang-multistage-test"],
          'builddir' :"clang-ppc64le-1",
          'factory' : ClangBuilder.getClangBuildFactory(triple='ppc64le-elf-linux',
                                                        useTwoStage=True, test=True,