Ticket #498 (closed bug: wontfix)

Opened 6 years ago

Last modified 5 years ago

Alignment test is unreliable on linux due to unaligned access fixups in kernel

Reported by: ccollins Owned by:
Priority: normal Milestone:
Component: configure Version: 1.0.0
Severity: low Keywords:
Cc: Language:
Patch status: rejected Platform: linux

Description

On ia64, alpha and a number of other archs, the Linux kernel installs a unaligned access fixup handler which hides unaligned accesses from userspace tasks. There is still a significant performance hit however.

Attached patch fixes the test under linux by disabling the fixup handler for that test if prctl() is available.

Attachments

parrot-linux-aligncheck-fix.diff Download (0.9 KB) - added by ccollins 6 years ago.
alignment check fixup patch for linux

Change History

Changed 6 years ago by ccollins

alignment check fixup patch for linux

follow-up: ↓ 2   Changed 6 years ago by doughera

Thanks for the patch. Fortunately, it doesn't really matter either way -- the result is only used for two ASSERT checks in unmanagedstruct.pmc, so there's no real performance impact.

It might be easier to just get rid of the whole Configure step.

in reply to: ↑ 1   Changed 5 years ago by jkeenan

  • status changed from new to closed
  • resolution set to wontfix
  • patch changed from new to rejected

Replying to doughera:

> Thanks for the patch.  Fortunately, it doesn't really matter either way -- 
> the result is only used for two ASSERT checks in unmanagedstruct.pmc, so 
> there's no real performance impact.  
> 
> It might be easier to just get rid of the whole Configure step.

I confirmed tonight what Andy D wrote nine months ago. On that basis, I'm going to reject this patch and close this ticket. However, I'm hoping a new ticket in which we can specifically consider getting rid of auto::alignptrs.

Thank you very much.
kid51

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