[SVN-4207] Speed up tmpfile creation

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: trunk
• Fix Version/s: ---
• Component/s: libsvn_subr
• Assignee: Unassigned
• Reporter: Subversion Importer
• Created: 19/Jul/12 15:58
• Updated: 27/Oct/18 16:28
• Resolved: 19/Jul/12 17:57

Description

(I've tried to send this patch to dev@, and user@ several weeks ago. None of
them seem to have made it to the lists. My best guess is they've ended up in
some moderator's /dev/null.)

Analyzing performance problems during the svn checkout of a project containing
several large directories--one with more than 1500 entries--, we've discovered
that libsvn_subr/io.c::svn_io_open_uniquely_named() is the culprit: When
creating temporary files in the prop-base subdirectory, the current
implementation leads to a high number of open() calls, proportional to the
square of the number of entries per directory. Most of these open() calls fail
with EEXIST.

Using a different scheme that essentially remembers (part of) the
last created temporary filename, most of these unsuccessful calls can be
avoided. (For the project in question, this reduced the total amount of
syscalls per checkout by almost 50 per cent, and significantly improved
checkout speed, especially on NFS filesystems where open() is relatively
expensive.)

Original issue reported by dkobras

Issue Links

• duplicates: SVN-3719 Extremely slow checkout on Windows