[llvm-dev] Buildbots timing out on full builds

Tue May 23 10:50:46 PDT 2017

Could you give https://reviews.llvm.org/differential/diff/99949/ <https://reviews.llvm.org/differential/diff/99949/> a try? It brings back the reverted commit and fixes two significant compile-time issues. Assuming it works for you too, I'll finish off the patches and post them individually.

The first one removes the single-use lambdas in the generated code. These turn out to be _really_ expensive. Replacing them with equivalent gotos saves 11 million allocations (~57%) during the course of compiling AArch64InstructionSelector.cpp.o. The cumulative number of bytes allocated also drops by ~4GB (~36%).

The second one is to split up the functions by the number of operands in the top-level instruction. This constrains the scale of the task the register allocator needs to deal with in X86InstructionSelection.cpp.o.

> On 22 May 2017, at 10:42, Diana Picus <diana.picus at linaro.org> wrote:
> 
> Nope, no sanitizers.
> 
> On 22 May 2017 at 11:38, Daniel Sanders <daniel_l_sanders at apple.com> wrote:
>> Is that with -fsanitize=memory too?
>> 
>> I'm currently building ToT with r303258 reverted. Once that's done I'll commit the revert and start investigating fixes.
>> 
>>> On 22 May 2017, at 10:22, Diana Picus <diana.picus at linaro.org> wrote:
>>> 
>>> Hi Daniel,
>>> 
>>> I did your experiment on a TK1 machine (same as the bots) and for r303258 I get:
>>> real    18m28.882s
>>> user    35m37.091s
>>> sys     0m44.726s
>>> 
>>> and for r303259:
>>> real    50m52.048s
>>> user    88m25.473s
>>> sys     0m46.548s
>>> 
>>> If I can help investigate, please let me know, otherwise we can just
>>> try your fixes and see how they affect compilation time.
>>> 
>>> Thanks,
>>> Diana
>>> 
>>> On 22 May 2017 at 10:49, Daniel Sanders <daniel_l_sanders at apple.com> wrote:
>>>> r303341 is the re-commit of the r303259 which tripled the number of rules
>>>> that can be imported into GlobalISel from SelectionDAG. A compile time
>>>> regression is to be expected but when I looked into it I found it was ~25s
>>>> on my machine for the whole incremental build rather than the ~12mins you
>>>> are seeing. I'll take another look.
>>>> 
>>>> I'm aware of a couple easy improvements we could make to the way the
>>>> importer works. I was leaving them until we change it over to a state
>>>> machine but the most obvious is to group rules by their top-level gMIR
>>>> instruction. This would reduce the cost of the std::sort that handles the
>>>> rule priorities in generating the source file and will also make it simpler
>>>> for the compiler to compile it.
>>>> 
>>>> 
>>>> On 21 May 2017, at 11:16, Vitaly Buka <vitalybuka at google.com> wrote:
>>>> 
>>>> It must be r303341, I commented on corresponding llvm-commits thread.
>>>> 
>>>> On Fri, May 19, 2017 at 7:34 AM, Diana Picus via llvm-dev
>>>> <llvm-dev at lists.llvm.org> wrote:
>>>>> 
>>>>> Ok, thanks. I'll try to do a bisect next week to see if I can find it.
>>>>> 
>>>>> Cheers,
>>>>> Diana
>>>>> 
>>>>> On 19 May 2017 at 16:29, Daniel Sanders <daniel_l_sanders at apple.com>
>>>>> wrote:
>>>>>> 
>>>>>>> On 19 May 2017, at 14:54, Daniel Sanders via llvm-dev
>>>>>>> <llvm-dev at lists.llvm.org> wrote:
>>>>>>> 
>>>>>>> r303259 will have increased compile-time since it tripled the number of
>>>>>>> importable
>>>>>>> SelectionDAG rules but a quick measurement building the affected file:
>>>>>>>  ninja
>>>>>>> lib/Target/<Target>/CMakeFiles/LLVM<Target>CodeGen.dir/<Target>InstructionSelector.cpp.o
>>>>>>> for both ARM and AArch64 didn't show a significant increase. I'll check
>>>>>>> whether
>>>>>>> it made a different to linking.
>>>>>> 
>>>>>> I don't think it's r303259. Starting with a fully built r303259, then
>>>>>> updating to r303258 and running 'ninja' gives me:
>>>>>>       real    2m28.273s
>>>>>>       user    13m23.171s
>>>>>>       sys     0m47.725s
>>>>>> then updating to r303259 and running 'ninja' again gives me:
>>>>>>       real    2m19.052s
>>>>>>       user    13m38.802s
>>>>>>       sys     0m44.551s
>>>>>> 
>>>>>>> sanitizer-x86_64-linux-fast also timed out after one of my commits this
>>>>>>> morning.
>>>>>>> 
>>>>>>>> On 19 May 2017, at 14:14, Diana Picus <diana.picus at linaro.org> wrote:
>>>>>>>> 
>>>>>>>> Hi,
>>>>>>>> 
>>>>>>>> We've noticed that recently some of our bots (mostly
>>>>>>>> clang-cmake-armv7-a15 and clang-cmake-thumbv7-a15) started timing out
>>>>>>>> whenever someone commits a change to TableGen:
>>>>>>>> 
>>>>>>>> r303418:
>>>>>>>> http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15/builds/7268
>>>>>>>> r303346:
>>>>>>>> http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15/builds/7242
>>>>>>>> r303341:
>>>>>>>> http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15/builds/7239
>>>>>>>> r303259:
>>>>>>>> http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15/builds/7198
>>>>>>>> 
>>>>>>>> TableGen changes before that (I checked about 3-4 of them) don't have
>>>>>>>> this problem:
>>>>>>>> r303253:
>>>>>>>> http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15/builds/7197
>>>>>>>> 
>>>>>>>> That one in particular actually finishes the whole build in 635s,
>>>>>>>> which is only a bit over 50% of the timeout limit (1200s). So, between
>>>>>>>> r303253 and now, something happened that made full builds
>>>>>>>> significantly slower. Does anyone have any idea what that might have
>>>>>>>> been? Also, has anyone noticed this on other bots?
>>>>>>>> 
>>>>>>>> Thanks,
>>>>>>>> Diana
>>>>>>> 
>>>>>>> _______________________________________________
>>>>>>> LLVM Developers mailing list
>>>>>>> llvm-dev at lists.llvm.org
>>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>> 
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>> 
>>>> 
>>>> 
>> 

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