Mercurial > hg

changeset 31587:ed5b25874d99 stable 4.1.2

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changegroup: store old heads as a set Previously, the "oldheads" variable was a list. On a repository at Mozilla with 46,492 heads, profiling revealed that list membership testing was dominating execution time of applying small changegroups. This patch converts the list of old heads to a set. This makes membership testing significantly faster. On the aforementioned repository with 46,492 heads: $ hg unbundle <file with 1 changeset> before: 18.535s wall after: 1.303s Consumers of this variable only check for truthiness (`if oldheads`), length (`len(oldheads)`), and (most importantly) item membership (`h not in oldheads` - which occurs twice). So, the change to a set should be safe and suitable for stable. The practical effect of this change is that changegroup application and related operations (like `hg push`) no longer exhibit an O(n^2) CPU explosion as the number of heads grows.
author Gregory Szorc <gregory.szorc@gmail.com>
date Thu, 23 Mar 2017 19:54:59 -0700
parents 2915cc1d3429
children 4baf79a77afa 8076499d292a
files mercurial/changegroup.py
diffstat 1 files changed, 1 insertions(+), 1 deletions(-) [+]
line wrap: on
line diff
--- a/mercurial/changegroup.py	Mon Mar 20 04:36:55 2017 -0700
+++ b/mercurial/changegroup.py	Thu Mar 23 19:54:59 2017 -0700
@@ -293,7 +293,7 @@
                 # will not see an inconsistent view
                 cl = repo.changelog
                 cl.delayupdate(tr)
-                oldheads = cl.heads()
+                oldheads = set(cl.heads())
 
                 trp = weakref.proxy(tr)
                 # pull off the changeset group