Patchwork [STABLE] partialdiscovery: avoid `undecided` related computation sooner than necessary

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Submitter Boris Feld
Date Jan. 24, 2019, 2:13 p.m.
Message ID <2ac72f1b08d3394c3db2.1548339194@localhost.localdomain>
Download mbox | patch
Permalink /patch/37959/
State Accepted
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Boris Feld - Jan. 24, 2019, 2:13 p.m.
# HG changeset patch
# User Boris Feld <boris.feld@octobus.net>
# Date 1548284862 18000
#      Wed Jan 23 18:07:42 2019 -0500
# Branch stable
# Node ID 2ac72f1b08d3394c3db21c1f576c189118b41eba
# Parent  c953c2a94d68b18c2f3c79262826fdfed743a839
# EXP-Topic discovery-regression
# Available At https://bitbucket.org/octobus/mercurial-devel/
#              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 2ac72f1b08d3
partialdiscovery: avoid `undecided` related computation sooner than necessary

Changeset 1d30be90c move the update of the `undecided` set within the
`partialdiscovery` object in order to clarify the API.

The update to the `undecided` set was unconditional in 1d30be90c and the first
access to the `self.undecided` property triggered the initial computation of
the set of undecided revisions. As a result, the set was computed much
earlier, at a time where less information is available, immediately followed
by an update of this set to remove common revisions.

To fix this regression, we ignore the `undecided` related logic in
`addcommons` when that `undecided` set has not been computed yet. Code that
actually needs to know the `undecided` set will trigger its computation later.
The change has no effects on semantic because the initial computation
`undecided` set takes all knowns `common` into account.

Example performance running `hg debugdiscovery` from a pypy repo missing 10
changesets:

870a89c6909d: 52.3ms (regression parent)
1d30be90c9dc: 72.0ms (regression)
5a5f504a7175: 64.8ms (this fix parent)
this fix:     52.6ms
via Mercurial-devel - Jan. 24, 2019, 5:19 p.m.
On Thu, Jan 24, 2019 at 6:15 AM Boris Feld <boris.feld@octobus.net> wrote:

> # HG changeset patch
> # User Boris Feld <boris.feld@octobus.net>
> # Date 1548284862 18000
> #      Wed Jan 23 18:07:42 2019 -0500
> # Branch stable
> # Node ID 2ac72f1b08d3394c3db21c1f576c189118b41eba
> # Parent  c953c2a94d68b18c2f3c79262826fdfed743a839
> # EXP-Topic discovery-regression
> # Available At https://bitbucket.org/octobus/mercurial-devel/
> #              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r
> 2ac72f1b08d3
> partialdiscovery: avoid `undecided` related computation sooner than
> necessary
>

Queued, thanks.


> Changeset 1d30be90c move the update of the `undecided` set within the
> `partialdiscovery` object in order to clarify the API.
>
> The update to the `undecided` set was unconditional in 1d30be90c and the
> first
> access to the `self.undecided` property triggered the initial computation
> of
> the set of undecided revisions. As a result, the set was computed much
> earlier, at a time where less information is available, immediately
> followed
> by an update of this set to remove common revisions.
>
> To fix this regression, we ignore the `undecided` related logic in
> `addcommons` when that `undecided` set has not been computed yet. Code that
> actually needs to know the `undecided` set will trigger its computation
> later.
> The change has no effects on semantic because the initial computation
> `undecided` set takes all knowns `common` into account.
>
> Example performance running `hg debugdiscovery` from a pypy repo missing 10
> changesets:
>
> 870a89c6909d: 52.3ms (regression parent)
> 1d30be90c9dc: 72.0ms (regression)
> 5a5f504a7175: 64.8ms (this fix parent)
> this fix:     52.6ms
>

For the record, I could repro with `hg *perf*discovery`:
before this patch: 0.006864
after this patch: 0.004141


>
> diff --git a/mercurial/setdiscovery.py b/mercurial/setdiscovery.py
> --- a/mercurial/setdiscovery.py
> +++ b/mercurial/setdiscovery.py
> @@ -183,7 +183,8 @@ class partialdiscovery(object):
>      def addcommons(self, commons):
>          """registrer nodes known as common"""
>          self._common.addbases(commons)
> -        self._common.removeancestorsfrom(self.undecided)
> +        if self._undecided is not None:
> +            self._common.removeancestorsfrom(self._undecided)
>
>      def addmissings(self, missings):
>          """registrer some nodes as missing"""
> _______________________________________________
> Mercurial-devel mailing list
> Mercurial-devel@mercurial-scm.org
> https://www.mercurial-scm.org/mailman/listinfo/mercurial-devel
>

Patch

diff --git a/mercurial/setdiscovery.py b/mercurial/setdiscovery.py
--- a/mercurial/setdiscovery.py
+++ b/mercurial/setdiscovery.py
@@ -183,7 +183,8 @@  class partialdiscovery(object):
     def addcommons(self, commons):
         """registrer nodes known as common"""
         self._common.addbases(commons)
-        self._common.removeancestorsfrom(self.undecided)
+        if self._undecided is not None:
+            self._common.removeancestorsfrom(self._undecided)
 
     def addmissings(self, missings):
         """registrer some nodes as missing"""