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gh-121267: Improve performance of tarfile (#121267) (#121269)

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Tarfile in the default write mode spends much of its time resolving UIDs
into usernames and GIDs into group names. By caching these mappings, a
significant speedup can be achieved.

In my simple benchmark[1], this extra caching speeds up tarfile by 8x.

[1] https://gist.github.com/jforberg/86af759c796199740c31547ae828aef2

---------

Co-authored-by: Tian Gao <gaogaotiantian@hotmail.com>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
This commit is contained in:
Johan Förberg 2024-10-30 23:08:30 +01:00 committed by GitHub
parent 616468b87b
commit 2b2d607095
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2 changed files with 19 additions and 8 deletions
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25
Lib/tarfile.py
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@ -1760,6 +1760,8 @@ class TarFile(object):
# current position in the archive file
self.inodes = {} # dictionary caching the inodes of
# archive members already added
self._unames = {} # Cached mappings of uid -> uname
self._gnames = {} # Cached mappings of gid -> gname
try:
if self.mode == "r":
@ -2138,16 +2140,23 @@ class TarFile(object):
tarinfo.mtime = statres.st_mtime
tarinfo.type = type
tarinfo.linkname = linkname
# Calls to pwd.getpwuid() and grp.getgrgid() tend to be expensive. To
# speed things up, cache the resolved usernames and group names.
if pwd:
try:
tarinfo.uname = pwd.getpwuid(tarinfo.uid)[0]
except KeyError:
pass
if tarinfo.uid not in self._unames:
try:
self._unames[tarinfo.uid] = pwd.getpwuid(tarinfo.uid)[0]
except KeyError:
self._unames[tarinfo.uid] = ''
tarinfo.uname = self._unames[tarinfo.uid]
if grp:
try:
tarinfo.gname = grp.getgrgid(tarinfo.gid)[0]
except KeyError:
pass
if tarinfo.gid not in self._gnames:
try:
self._gnames[tarinfo.gid] = grp.getgrgid(tarinfo.gid)[0]
except KeyError:
self._gnames[tarinfo.gid] = ''
tarinfo.gname = self._gnames[tarinfo.gid]
if type in (CHRTYPE, BLKTYPE):
if hasattr(os, "major") and hasattr(os, "minor"):

2
Misc/NEWS.d/next/Library/2024-07-02-15-56-42.gh-issue-121267.yFBWkh.rst Normal file
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@ -0,0 +1,2 @@
Improve the performance of :mod:`tarfile` when writing files, by caching user names
and group names.