patchgrep - Patches: patch #3803, Red Hat's "egf-speedup"...


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patch #3803: Red Hat's "egf-speedup" patch

Submitted by:  Charles Levert <charles_levert>
Submitted on:  Tue 08 Mar 2005 12:08:24 PM UTC  
Category:  None Priority:  5 - Normal
Status:  Wont Do Privacy:  Public
Assigned to:  None Open/Closed:  Closed

Thu 14 Jul 2011 09:15:55 AM UTC, comment #4:

The patch won't be merged as is. Cases providing bad performance will be examined as they arise.

Paolo Bonzini <bonzini>
Mon 08 Mar 2010 05:03:21 PM UTC, comment #3:

The problem is that this patch is a black box and nobody understands what it really does.

So this should be reevaluated after the 2.6 release (on top of which egf-speedup likely won't apply...). Hopefully the distros will provide testcases that really need this patch and we can look into them.

Paolo Bonzini <bonzini>
Thu 28 Apr 2005 12:16:27 PM UTC, comment #2:

The full story behind this patch is that grep-2.5.1a does not handle UTF-8 gracefully at all. The basic plan with handling UTF-8 in 2.5.1a is:

  • whenever a buffer is parsed, go through the entire buffer deciding how many bytes make up each character
  • use this information when necessary

This patch changes that to:

  • when information about how many bytes make up a character is needed, work it out on demand

On the face of it, this is a small obvious improvement. In fact it is much better than that, because the original scheme would calculate character lengths several times for each buffer: in fact, one full pass for every single potential match!

For a full discussion of this patch, as well as dfa-optional, including benchmarking results, see the mailing list.

Tim Waugh <twaugh>
Thu 28 Apr 2005 11:50:22 AM UTC, comment #1:

Tim Waugh wrote of grep-2.5.1-gofast.patch (patch #3478), from which this patch is derived, "I wrote this to partially address bug #69900 (grep writing output very slow): ".

Julian Foad <julianfoad>
Tue 08 Mar 2005 12:08:24 PM UTC, original submission:

This item is created to document in Savannah the existence of the following patch from Red Hat/Fedora:

Here is the relevant log content:
* Fri Jan 7 2005 Tim Waugh <>
- Cache MB_CUR_MAX value in egf-speedup patch.
* Fri Jan 7 2005 Tim Waugh <>
- Fixed variable shadowing in egf-speedup patch.
* Fri Dec 31 2004 Tim Waugh <>
- Jakub Jelinek's much improved -Fi algorithm.
* Tue Dec 21 2004 Tim Waugh <> 2.5.1-44
- Fixed -Fi for multibyte input (bug #143079).
* Thu Dec 16 2004 Tim Waugh <>
- Bypass kwset matching when ignoring case and processing multibyte input (bug #143079).
* Thu Dec 16 2004 Tim Waugh <>
- Bypass kwset matching when ignoring case and processing multibyte input (bug #143079).
* Tue Dec 14 2004 Tim Waugh <> 2.5.1-42
- Further UTF-8 processing avoided since a '\n' byte is always an end-of-line character in that encoding.
* Fri Dec 3 2004 Tim Waugh <> 2.5.1-41
- Fixed a busy loop in the egf-speedup patch (bug #140781).
Functional equivalence with pre-patched package.
* Thu Nov 4 2004 Tim Waugh <> 2.5.1-34
- More improvements to egf-speedup patch (bug #138076).
* Thu Nov 4 2004 Tim Waugh <> 2.5.1-33
- Small improvements to egf-speedup patch.
* Wed Nov 3 2004 Tim Waugh <> 2.5.1-32
- Remove mb-caching hack.
- Better multibyte handling in EGexecute().
- Don't need regex.c changes in grep-2.5-i18n.patch.

Charles Levert <charles_levert>


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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2011-07-14 bonzini StatusPostponed => Wont Do
        Open/ClosedOpen => Closed
    2010-03-08 bonzini StatusNone => Postponed

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