[PATCH 1 of 2] patchcopies: give up any optimization based on `introrev`

[Yuya Nishihara]

On Sun, 13 Oct 2019 23:02:25 +0200, Pierre-Yves David wrote:
> On 10/13/19 12:08 PM, Yuya Nishihara wrote:
> > On Fri, 11 Oct 2019 20:00:58 +0200, Pierre-Yves David wrote:
> >> On 10/11/19 2:02 PM, Yuya Nishihara wrote:
> >>> On Fri, 11 Oct 2019 01:04:12 +0200, Pierre-Yves David wrote:
> >>>> # HG changeset patch
> >>>> # User Pierre-Yves David <pierre-yves.david at octobus.net>
> >>>> # Date 1570672173 -7200
> >>>> #      Thu Oct 10 03:49:33 2019 +0200
> >>>> # Node ID 2477ba483c04067900d1e9f6523b03df68a4d545
> >>>> # Parent  8ff1ecfadcd110849c47c77e31c92809eea466ab
> >>>> # EXP-Topic patchcopies-regression
> >>>> # Available At https://bitbucket.org/octobus/mercurial-devel/
> >>>> #              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 2477ba483c04
> >>>> patchcopies: give up any optimization based on `introrev`
> >>>>
> >>>> Between 8a0136f69027 and d98fb3f42f33, we sped up the search for the
> >>>> introduction revision during path copies. However, further checking show that
> >>>> finding the introduction revision is still expensive and that we are better off
> >>>> without it. So we simply drop it and only rely on the linkrev optimisation.
> >>>>
> >>>> I ran `perfpathcopies` on 6989 pair of revision in the pypy
> >>>> repository (`hg perfhelper-pathcopies`. The result is massively in favor of
> >>>> dropping this condition. The result of the copy tracing are unchanged.
> >>>>
> >>>> Attempt to use a smaller changes preserving linkrev usage were unsuccessful, it
> >>>> can return wrong result. The following changesets broke test-mv-cp-st-diff.t
> >>>>
> >>>>       -        if not f.isintroducedafter(limit):
> >>>>       +        if limit >= 0 and f.linkrev() < limit:
> >>>>                    return None
> >>>
> >>> Sure. I meant comparing linkrevs, not linkrev vs (changelog) rev. If both
> >>> arms were linkrevs, and if the limit pointed to the revision where the
> >>> linkrevs of its files are guaranteed to be the lowest, the comparison
> >>> (e.g. f.linkrev() < repo[limit][path].linkrev()) would work.
> >>>
> >>> My question was whether it would make things fast or not.
> >>
> >> Ha, I understand your proposal better now.
> >>
> >> My testing of the version in this patch versus the "wrong" version using
> >> linkrev too agressively did not show a significant difference (-1%).
> > 
> > Do you mean only 1% speedup or measurable speedup on 1% cases? I don't think
> > the former is significant, but the latter could be depending on use cases.
> 
> only ±1% speedup for all (many) cases I looked at.
> 
> >> So
> >> I don't it to raise anything better. Can we move forward with this
> >> series and maybe try a different approach later ?
> > 
> > Better to leave the _findlimit() function? Or won't it be any useful in
> > your future work?
> 
> That seems easy enough t reintroduce later if needed. My current 
> optimization work focus on the changeset based copies tracing algorithm. 
> I don't think I'll spend much time on the filelog based one.

Fair enough. Queued the series, thanks.