Benchmarking lexical scan during the downsweep for the ImplicitQualifiedImport proposal

[Tristan Cacqueray]

Thank you Matt, that's exactly what I was looking for.

The `--make GHC` command failed because of hidden packages, and adding
the list of `-package-id` arguments used by hadrian fixed the errors.
For the record, here is the full invocation I got working:
  https://gitlab.haskell.org/TristanCacqueray/ghc/-/blob/make-lexical-analysis/build-ghc.sh

-Tristan

On Mon, Aug 29, 2022 at 10:08 Matthew Pickering wrote:
> 1. You want to test this in the context of recompilation, that is
> where the cost of downsweep is most prominent. Ie, compile all the
> modules normally once and then test how long it takes to recompile.
> There is already a test in tree which does this
> (MultiLayerModulesRecomp).
>
> 2. You can build GHC using `--make` mode with an invocation something like..
>
>  $GHC -O -hidir $out -odir $out -i$dir -Icompiler
> -I_perf/stage1/compiler/build/ -i_perf/stage1/compiler/build/ GHC
> -XNoImplicitPrelude -XNoPolyKinds -O
>
> 3. The way to extract timing information is to use the `+RTS -s` option.
>
> Matt
>
>
> On Sun, Aug 28, 2022 at 7:55 PM Tristan Cacqueray <tdecacqu at redhat.com> wrote:
>>
>>
>> Hello all,
>>
>> In the context of https://github.com/ghc-proposals/ghc-proposals/pull/500,
>> I am looking for a strategy to measure the impact of resolving modules
>> dependencies using a lexical scan during the downsweep phase.
>>
>> For example, in this branch: https://gitlab.haskell.org/TristanCacqueray/ghc/-/tree/make-lexical-analysis
>> I've added a tokenizer pass in the GHC.Driver.Make.getPreprocessedImports function,
>> and using `/usr/bin/time -o /dev/stdout -v _build/stage1/bin/ghc compiler/GHC/Tc/TyCl.hs 2> /dev/null`
>> I measure:
>>
>>   LexicalAnalysis found 91 qualified name, and lasted: 150msec
>>   Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.72
>>   Maximum resident set size (kbytes): 142396
>>
>> Using a clean build I get:
>>
>>   Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.68
>>   Maximum resident set size (kbytes): 140012
>>
>>
>> Now my question is, how would you measure the time and space cost of
>> such change. For example, what profiling tool would you recommend and
>> how can I test a modified ghc to build ghc itself?
>>
>> Thanks in advance,
>> -Tristan
>> _______________________________________________
>> ghc-devs mailing list
>> ghc-devs at haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 515 bytes
Desc: not available
URL: <http://mail.haskell.org/pipermail/ghc-devs/attachments/20220829/22657be9/attachment.sig>