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Add option to run debug memory backend without issuing errors #4882

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@victor-decaria-nnl victor-decaria-nnl commented Jun 5, 2025 •
edited by tzanio
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This adds a runtime option so that the debug backend won't use mprotect statements if MFEM_MMU_SILENT is in the environment.

The motivation for this is if you're debugging but you suspect that the mprotect logic is causing false postives, you can disable the mprotect calls and still emulate the host-device transfers.

I thought about seeing if I could make debug-silent an acceptable string but wasn't sure where that plugged in and this is similar to the way MFEM_MMU_PROTECT_ERROR is currently used.

PR Author Editor Reviewers Assignment Approval Merge
#4882 @victor-decaria-nnl @tzanio @camierjs + @v-dobrev 6/8/25 ⌛due 6/22/25 ⌛due 6/29/25
PR Checklist
  • Code builds.
  • Code passes make style.
  • Update CHANGELOG:
    • Is this a new feature users need to be aware of? New or updated example or miniapp?
    • Does it make sense to create a new section in the CHANGELOG to group with other related features?
  • Update INSTALL:
    • Had a new optional library been added? If so, what range of versions of this library are required? (Make sure the external library is compatible with our BSD license, e.g. it is not licensed under GPL!)
    • Have the version ranges for any required or optional libraries changed?
    • Does make or cmake have a new target?
    • Did the requirements or the installation process change? (rare)
  • Update continuous integration server configurations if necessary (e.g. with new version requirements for each of MFEM's dependencies)
    • .github
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  • Update .gitignore:
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    • Add new patterns (just for the new files above) and re-run the above test.
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      • Add a short description of the example in the "Extensive Examples" section of features.md.
  • New miniapps:
    • All sample runs at the top of the miniapp source file work.
    • Update top-level makefile and makefile in corresponding miniapp directory.
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      • The miniapps go at the end of the page, and are usually listed only under a specific "Application (PDE)" category.
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  • Update this checklist, if the new pull request affects it.
  • Run make unittest to make sure all unit tests pass.
  • Run the tests in tests/scripts.
  • (LLNL only) After merging:
    • Update internal tests to include the new features.

@victor-decaria-nnl victor-decaria-nnl self-assigned this Jun 5, 2025
@victor-decaria-nnl victor-decaria-nnl marked this pull request as ready for review June 5, 2025 15:53
@tzanio
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tzanio commented Jun 8, 2025

This PR is now under review (see the table in the PR description). To help with the review process, please do not force push to the branch.

@tzanio tzanio requested a review from v-dobrev June 8, 2025 23:35
@tzanio tzanio added the GPU label Jun 8, 2025
@github-project-automation github-project-automation bot moved this to Review Now in Pull Requests Jun 8, 2025
@tzanio tzanio added this to the mfem-4.9 milestone Jun 8, 2025
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camierjs commented Jun 10, 2025 •
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Thank you @victor-decaria-nnl for bringing this option: I can see the use of it.

If we want to silence the MMU and skip all the mprotect calls, we can also use the StdHostMemorySpace and StdDeviceMemorySpace while selecting the memory controllers in NewHostCtrl:

case MT::HOST_DEBUG:
   if (GetEnv("MFEM_MMU_STD")) { return new StdHostMemorySpace(); }
   return new MmuHostMemorySpace();

and

case MT::DEVICE_DEBUG:
   if (GetEnv("MFEM_MMU_STD")) { return new StdDeviceMemorySpace(); }
   return new MmuDeviceMemorySpace();

It allows you to skip all the address computations, which overall gives a good speedup.

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@camierjs camierjs Awaiting requested review from camierjs

@v-dobrev v-dobrev Awaiting requested review from v-dobrev

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@tzanio tzanio

@v-dobrev v-dobrev

@camierjs camierjs

@victor-decaria-nnl victor-decaria-nnl

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