Mercurial > hg
diff mercurial/changegroup.py @ 31587:ed5b25874d99 stable 4.1.2
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 | 2df983125d37 |
children | 4baf79a77afa |
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--- 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