[llvm-dev] lld and thread over-subscription
Hal Finkel via llvm-dev
llvm-dev at lists.llvm.org
Thu Oct 1 10:26:53 PDT 2015
----- Original Message -----
> From: "Rui Ueyama" <ruiu at google.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: "LLVM Developers" <llvm-dev at lists.llvm.org>, "Rafael Espindola" <rafael.espindola at gmail.com>
> Sent: Thursday, October 1, 2015 11:46:05 AM
> Subject: Re: lld and thread over-subscription
>
> On Thu, Oct 1, 2015 at 9:35 AM, Hal Finkel < hfinkel at anl.gov > wrote:
>
> Hi Rui, et al.,
>
> I was experimenting yesterday with building lld on my POWER7
> PPC64/Linux machine, and ran into an unfortunate problem. When
> running the regressions tests under lit, almost all of the tests
> fail like this:
>
> terminate called after throwing an instance of 'std::system_error'
> what(): Resource temporarily unavailable
> ...
> 5 libc.so.6 0x00000080b7847238 abort + 4293480680
> 6 libstdc++.so.6 0x00000fff94f0f004
> __gnu_cxx::__verbose_terminate_handler() + 4294099316
> 7 libstdc++.so.6 0x00000fff94f0bc84
> 8 libstdc++.so.6 0x00000fff94f0bccc std::terminate() + 4294087956
> 9 libstdc++.so.6 0x00000fff94f0c0c4 __cxa_throw + 4294088780
> 10 libstdc++.so.6 0x00000fff94f816e0 std::__throw_system_error(int) +
> 4294526808
> 11 libstdc++.so.6 0x00000fff94f83d30
> std::thread::_M_start_thread(std::shared_ptr<std::thread::_Impl_base>)
> + 4294534936
> 12 lld 0x000000001002a278
> ...
>
> which seems to indicate a core problem here with dealing with
> thread-resource exhaustion. For almost all tests, running them
> individually (or using lit -j 1) works without a problem. We could
> deal with this by limiting the number of threads lld uses when
> running regression tests, or limit the number of threads that lit
> uses when running lld tests (as we currently do with the OpenMP
> runtime tests), but I'm somewhat concerned that users will run into
> this program regardless with heavily-parallelized builds.
>
> We could try to catch exceptions that otherwise come from
> ThreadPoolExecutor's constructor, but do we compile with exceptions
> enabled?
>
> I guess we do not want to enable exceptions to deal with the issue.
> Are COFF tests failing, or just ELF tests? If ELF tests for the old
> LLD are failing, the best way would be to not use threads in the old
> LLD. It has lingering threading issues.
>
To provide a data point; my default environment has this:
$ ulimit -a | grep proc
max user processes (-u) 1024
This machine has 48 cores, so with lit running 48 tests leaves each test with only about 20 available threads, much less than the 48 each test believes it can use.
This is somewhat non-deterministic, but I just reran things both ways, and here's what I see:
During my last run, these tests fail when running under lit with many parallel tests, but do not fail when run otherwise:
lld :: elf2/basic.s
lld :: elf/AArch64/general-dyn-tls-0.test
lld :: elf/AArch64/initial-exec-tls-0.test
lld :: elf/AArch64/rel-prel32-overflow.test
lld :: elf/AArch64/rel-prel64.test
lld :: elf/AMDGPU/hsa.test
lld :: elf/ARM/arm-symbols.test
lld :: elf/ARM/dynamic-symbols.test
lld :: elf/ARM/entry-point.test
lld :: elf/ARM/exidx.test
lld :: elf/ARM/header-flags.test
lld :: elf/ARM/mapping-code-model.test
lld :: elf/ARM/mapping-symbols.test
lld :: elf/ARM/missing-symbol.test
lld :: elf/ARM/plt-dynamic.test
lld :: elf/ARM/plt-ifunc-interwork.test
lld :: elf/ARM/plt-ifunc-mapping.test
lld :: elf/ARM/rel-arm-call.test
lld :: elf/ARM/rel-arm-jump24-veneer-b.test
lld :: elf/ARM/rel-arm-mov.test
lld :: elf/ARM/rel-arm-prel31.test
lld :: elf/ARM/rel-arm-target1.test
lld :: elf/ARM/rel-arm-thm-interwork.test
lld :: elf/ARM/undef-lazy-symbol.test
lld :: elf/Hexagon/dynlib-data.test
lld :: elf/Mips/exe-dynamic.test
lld :: elf/Mips/exe-dynsym.test
lld :: elf/Mips/exe-fileheader-64.test
lld :: elf/Mips/exe-fileheader-micro-64.test
lld :: elf/Mips/exe-fileheader-n32.test
lld :: elf/Mips/exe-got-micro.test
lld :: elf/Mips/exe-got.test
lld :: elf/Mips/got16-2.test
lld :: elf/Mips/got16-micro.test
lld :: elf/Mips/got-page-32-micro.test
lld :: elf/Mips/got-page-64-micro.test
lld :: elf/Mips/got-page-64.test
lld :: elf/X86_64/sectionchoice.test
lld :: elf/X86_64/sectionmap.test
lld :: mach-o/arm-interworking.yaml
lld :: mach-o/arm-shims.yaml
lld :: mach-o/data-only-dylib.yaml
lld :: mach-o/executable-exports.yaml
lld :: mach-o/exe-offsets.yaml
lld :: mach-o/exported_symbols_list-undef.yaml
lld :: mach-o/fat-archive.yaml
lld :: mach-o/flat_namespace_undef_error.yaml
lld :: mach-o/flat_namespace_undef_suppress.yaml
lld :: mach-o/force_load-x86_64.yaml
lld :: mach-o/got-order.yaml
lld :: mach-o/hello-world-arm64.yaml
lld :: mach-o/hello-world-armv6.yaml
lld :: mach-o/hello-world-x86_64.yaml
lld :: mach-o/hello-world-x86.yaml
lld :: mach-o/keep_private_externs.yaml
lld :: mach-o/lazy-bind-x86_64.yaml
lld :: mach-o/library-rescan.yaml
lld :: mach-o/mh_bundle_header.yaml
lld :: mach-o/mh_dylib_header.yaml
lld :: mach-o/objc_export_list.yaml
lld :: mach-o/order_file-basic.yaml
lld :: mach-o/parse-aliases.yaml
lld :: mach-o/parse-cfstring32.yaml
lld :: mach-o/parse-cfstring64.yaml
lld :: mach-o/parse-compact-unwind32.yaml
lld :: mach-o/parse-compact-unwind64.yaml
lld :: mach-o/parse-data-in-code-armv7.yaml
lld :: mach-o/parse-data-in-code-x86.yaml
lld :: mach-o/parse-data-relocs-arm64.yaml
lld :: mach-o/parse-data-relocs-x86_64.yaml
lld :: mach-o/parse-data.yaml
lld :: mach-o/parse-eh-frame-relocs-x86_64.yaml
lld :: mach-o/parse-eh-frame-x86-anon.yaml
lld :: mach-o/parse-eh-frame-x86-labeled.yaml
lld :: mach-o/parse-eh-frame.yaml
lld :: mach-o/parse-function.yaml
lld :: mach-o/parse-initializers32.yaml
lld :: mach-o/parse-initializers64.yaml
lld :: mach-o/parse-literals-error.yaml
lld :: mach-o/parse-literals.yaml
lld :: mach-o/parse-non-lazy-pointers.yaml
lld :: mach-o/parse-relocs-x86.yaml
lld :: mach-o/parse-section-no-symbol.yaml
lld :: mach-o/parse-tentative-defs.yaml
lld :: mach-o/parse-text-relocs-x86_64.yaml
lld :: mach-o/parse-tlv-relocs-x86-64.yaml
lld :: mach-o/re-exported-dylib-ordinal.yaml
lld :: mach-o/rpath.yaml
lld :: mach-o/run-tlv-pass-x86-64.yaml
lld :: mach-o/sectalign.yaml
lld :: mach-o/twolevel_namespace_undef_dynamic_lookup.yaml
lld :: mach-o/usage.yaml
lld :: mach-o/use-simple-dylib.yaml
lld :: mach-o/write-final-sections.yaml
lld :: mach-o/wrong-arch-error.yaml
lld-Unit :: CoreTests/CoreTests/Range.conversion_to_pointer_range
lld-Unit :: CoreTests/CoreTests/Range.slice
lld-Unit :: CoreTests/CoreTests/Range.user1
lld-Unit :: CoreTests/CoreTests/Range.user2
Of these, the following tests don't fail, but are reported as 'Unresolved' (which does not happen if I run lit -j 1):
lld :: elf/ARM/mapping-code-model.test
lld :: elf/ARM/mapping-symbols.test
lld :: elf/ARM/missing-symbol.test
lld :: elf/ARM/plt-ifunc-interwork.test
lld :: elf/ARM/rel-arm-jump24-veneer-b.test
lld :: elf/Mips/exe-got-micro.test
lld :: elf/Mips/exe-got.test
lld :: elf/Mips/got16-micro.test
lld :: mach-o/parse-cfstring64.yaml
lld :: mach-o/parse-compact-unwind32.yaml
lld :: mach-o/parse-compact-unwind64.yaml
lld :: mach-o/parse-data-in-code-armv7.yaml
lld :: mach-o/parse-data-in-code-x86.yaml
lld :: mach-o/parse-data-relocs-arm64.yaml
lld :: mach-o/parse-data-relocs-x86_64.yaml
lld :: mach-o/parse-data.yaml
lld :: mach-o/parse-eh-frame-relocs-x86_64.yaml
lld :: mach-o/parse-eh-frame-x86-anon.yaml
lld :: mach-o/parse-eh-frame-x86-labeled.yaml
lld :: mach-o/parse-eh-frame.yaml
lld :: mach-o/parse-function.yaml
lld :: mach-o/parse-initializers32.yaml
lld :: mach-o/parse-initializers64.yaml
lld :: mach-o/parse-literals-error.yaml
lld :: mach-o/parse-literals.yaml
lld :: mach-o/parse-non-lazy-pointers.yaml
lld :: mach-o/parse-relocs-x86.yaml
lld :: mach-o/parse-section-no-symbol.yaml
lld :: mach-o/parse-tentative-defs.yaml
lld :: mach-o/parse-text-relocs-arm64.yaml
lld :: mach-o/parse-text-relocs-x86_64.yaml
lld :: mach-o/parse-tlv-relocs-x86-64.yaml
lld :: mach-o/rpath.yaml
lld :: mach-o/run-tlv-pass-x86-64.yaml
lld :: mach-o/twolevel_namespace_undef_dynamic_lookup.yaml
lld :: mach-o/usage.yaml
lld-Unit :: CoreTests/CoreTests/Range.conversion_to_pointer_range
lld-Unit :: CoreTests/CoreTests/Range.slice
lld-Unit :: CoreTests/CoreTests/Range.user1
lld-Unit :: CoreTests/CoreTests/Range.user2
these are listed as unresolved for the same underlying reason, for example:
********************
UNRESOLVED: lld-Unit :: CoreTests/CoreTests/Range.user1 (25040 of 25181)
******************** TEST 'lld-Unit :: CoreTests/CoreTests/Range.user1' FAILED ********************
Exception during script execution:
Traceback (most recent call last):
File "/src/llvm/utils/lit/lit/run.py", line 166, in execute_test
result = test.config.test_format.execute(test, self.lit_config)
File "/src/llvm/utils/lit/lit/formats/googletest.py", line 113, in execute
cmd, env=test.config.environment)
File "/src/llvm/utils/lit/lit/util.py", line 166, in executeCommand
env=env, close_fds=kUseCloseFDs)
File "/install/ppc64/Python-2.7/lib/python2.7/subprocess.py", line 710, in __init__
errread, errwrite)
File "/install/ppc64/Python-2.7/lib/python2.7/subprocess.py", line 1231, in _execute_child
self.pid = os.fork()
OSError: [Errno 11] Resource temporarily unavailable
Being naturally nondeterministic, running again with the default number of parallel lit tests changes which tests fail (for example, running a second time adds tests under COFF).
And, FWIW, these tests generally fail on my system (for reasons seemingly unrelated to the thread/process resource issue):
lld :: Driver/lib-search.test
lld :: Driver/undef-basic.objtxt
lld :: elf2/dynamic-reloc.s
lld :: elf2/shared.s
lld :: elf2/soname.s
lld :: elf/librarynotfound.test
lld :: elf/responsefile.test
lld :: mach-o/dylib-install-names.yaml
lld :: mach-o/force_load-dylib.yaml
lld :: mach-o/lib-search-paths.yaml
lld :: mach-o/parse-text-relocs-arm64.yaml
lld :: mach-o/upward-dylib-load-command.yaml
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.AsNeeded
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.DefsymAlias
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.DefsymDecimal
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.DefsymHexadecimal
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.DefsymOctal
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.Empty
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.Entry
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.EntryJoined
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.EntryShort
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.ExportDynamic
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.Init
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.InitJoined
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.NoExportDynamic
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.NoinhibitExec
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.Output
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.OutputDefault
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.Rpath
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.RpathEq
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.SOName
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.SONameH
lld-Unit :: DriverTests/DriverTests/GnuLdParserTest.SONameSingleDash
lld-Unit :: DriverTests/DriverTests/LinkerScriptTest.Entry
lld-Unit :: DriverTests/DriverTests/LinkerScriptTest.ExprEval
lld-Unit :: DriverTests/DriverTests/LinkerScriptTest.Group
lld-Unit :: DriverTests/DriverTests/LinkerScriptTest.IgnoreSearchDirNoStdLib
lld-Unit :: DriverTests/DriverTests/LinkerScriptTest.Input
lld-Unit :: DriverTests/DriverTests/LinkerScriptTest.Output
lld-Unit :: DriverTests/DriverTests/LinkerScriptTest.SearchDir
lld-Unit :: DriverTests/DriverTests/UniversalDriver.flavor
(it could be big-Endian issues, LLVM bugs, etc. -- I've yet to investigate).
The easiest thing to do is to make lld tests run using lit -j 1, but we may also want to think about how to more-gracefully handle this situation in general, because it seems like something a user is not unlikely to hit.
Thanks again,
Hal
>
> Thanks again,
> Hal
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
>
>
--
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory
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