https://github.com/python/cpython/commit/6efd95c4650ec7c2fb5522b352c74a9d44370fe0 commit: 6efd95c4650ec7c2fb5522b352c74a9d44370fe0 branch: main author: morotti <[email protected]> committer: gpshead <[email protected]> date: 2024-10-04T16:51:22-07:00 summary:
gh-117151: increase default buffer size of shutil.copyfileobj() to 256k. (GH-119783) * gh-117151: increase default buffer size of shutil.copyfileobj() to 256k. it was set to 16k in the 1990s. it was raised to 64k in 2019. the discussion at the time mentioned another 5% improvement by raising to 128k and settled for a very conservative setting. it's 2024 now, I think it should be revisited to match modern hardware. I am measuring 0-15% performance improvement when raising to 256k on various types of disk. there is no downside as far as I can tell. this function is only intended for sequential copy of full files (or file like objects). it's the typical use case that benefits from larger operations. for reference, I came across this function while trying to profile pip that is using it to copy files when installing python packages. * add news --------- Co-authored-by: rmorotti <[email protected]> files: A Misc/NEWS.d/next/Library/2024-10-03-05-00-25.gh-issue-117151.Prdw_W.rst M Lib/shutil.py diff --git a/Lib/shutil.py b/Lib/shutil.py index dab3ca5ee91245..dd3e0e0c5da54b 100644 --- a/Lib/shutil.py +++ b/Lib/shutil.py @@ -44,7 +44,7 @@ else: _winapi = None -COPY_BUFSIZE = 1024 * 1024 if _WINDOWS else 64 * 1024 +COPY_BUFSIZE = 1024 * 1024 if _WINDOWS else 256 * 1024 # This should never be removed, see rationale in: # https://bugs.python.org/issue43743#msg393429 _USE_CP_SENDFILE = (hasattr(os, "sendfile") diff --git a/Misc/NEWS.d/next/Library/2024-10-03-05-00-25.gh-issue-117151.Prdw_W.rst b/Misc/NEWS.d/next/Library/2024-10-03-05-00-25.gh-issue-117151.Prdw_W.rst new file mode 100644 index 00000000000000..a7d6251f1e071f --- /dev/null +++ b/Misc/NEWS.d/next/Library/2024-10-03-05-00-25.gh-issue-117151.Prdw_W.rst @@ -0,0 +1,3 @@ +The default buffer size used by :func:`shutil.copyfileobj` has been +increased from 64k to 256k on non-Windows platforms. It was already larger +on Windows. _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3/lists/python-checkins.python.org/ Member address: [email protected]
