[llvm-dev] Buildbots timing out on full builds

Daniel Sanders via llvm-dev llvm-dev at lists.llvm.org
Wed May 31 01:21:17 PDT 2017 

Hi Diana and Vitaly,

Could you give https://reviews.llvm.org/differential/diff/100829/ <https://reviews.llvm.org/differential/diff/100829/> a try? When measuring the compile of AArch64InstructionSelector.cpp.o with asan enabled and running under instruments's Allocation profiler, my machine reports that the cumulative memory allocations is down to ~3.5GB (was ~10GB), the number of allocations down to ~4 million (was ~23 million), and the compile time down to ~15s (was ~60s).

The patch is based on r303542 and the main change is that most of the generated C++ has been replaced with a state-machine based implementation. It's not fully converted to a state-machine yet since it generates lots of smaller machines (one matcher and one emitter per rule) instead of a single machine but it's hopefully sufficient to unblock my patch series.

> On 26 May 2017, at 09:10, Diana Picus <diana.picus at linaro.org> wrote:
> 
> Ok, that sounds reasonable. I'm happy to test more patches for you
> when they're ready.
> 
> On 25 May 2017 at 17:39, Daniel Sanders <daniel_l_sanders at apple.com> wrote:
>> Thanks for trying that patch. I agree that 34 mins still isn't good enough but we're heading in the right direction.
>> 
>> Changing the partitioning predicate to the instruction opcode rather than the number of operands in the top-level instruction will hopefully cut it down further. I also have a patch that shaves a small amount off of the compile-time by replacing the various LLT::scalar()/LLT::vector() calls with references to LLT objects that were created in advance. I tried something similar with the getRegBankForRegClass() but I haven't written that as a patch yet since that one requires some refactors to get access to a mapping that RegisterBankEmitter.cpp knows. In my experiment I edited this information into AArchGenGlobalISel.inc by hand.
>> 
>> I think the real solution is to convert the generated C++ to the state-machine that we intended to end up with. I don't think we'll be able to put it off much longer given that we're hitting compile-time problems when we can only import 25% of the rules. That said, I have a couple more nearly-finished patches I'd like to get in before we introduce the state machine. Hopefully, the above tricks will be enough to save me a re-write.
>> 
>>> On 25 May 2017, at 16:11, Diana Picus <diana.picus at linaro.org> wrote:
>>> 
>>> Hi Daniel,
>>> 
>>> I built r303542, then applied your patch and built again and it still takes
>>> real    34m30.279s
>>> user    84m36.553s
>>> sys     0m58.372s
>>> 
>>> This is better than the 50m I saw before, but I think we should try to
>>> make it a bit faster. Do you have any other ideas to make it work?
>>> 
>>> Thanks,
>>> Diana
>>> 
>>> 
>>> On 22 May 2017 at 11:22, 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
>>>>> 
>>>>> 
>>>>> 
>> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170531/6776b217/attachment.html>

More information about the llvm-dev mailing list