Skip to content

gh-129205: Update multiprocessing.forkserver to use os.readinto #129425

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 6 commits into from
Jan 30, 2025
Merged

gh-129205: Update multiprocessing.forkserver to use os.readinto #129425

Show file tree
Hide file tree
Changes from 5 commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
4f452fe
gh-129205: Update multiprocessing.forkserver to use os.readinto
cmaloney Jan 29, 2025
d2d5baf
Update 2025-01-28-22-11-41.gh-issue-129205.C-vE8S.rst
cmaloney Jan 29, 2025
9227d4e
Rework loop to only use one read in got it all case
cmaloney Jan 29, 2025
4409ae3
Work in positives
cmaloney Jan 29, 2025
3ef05ba
Rely on memoryview to track length, reduce temporaries
cmaloney Jan 29, 2025
22e6821
Remove news
cmaloney Jan 30, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 7 additions & 6 deletions Lib/multiprocessing/forkserver.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -382,13 +382,14 @@ def _serve_one(child_r, fds, unused_fds, handlers):
#

def read_signed(fd):
data = b''
length = SIGNED_STRUCT.size
while len(data) < length:
s = os.read(fd, length - len(data))
if not s:
data = bytearray(SIGNED_STRUCT.size)
unread = memoryview(data)
while unread:
count = os.readinto(fd, unread)
if count == 0:
raise EOFError('unexpected EOF')
data += s
unread = unread[count:]

return SIGNED_STRUCT.unpack(data)[0]

def write_signed(fd, n):
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-01-28-22-11-41.gh-issue-129205.C-vE8S.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
:mod:`multiprocessing` forkserver now uses :func:`os.readinto` to read pid
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I don't think that it's worth it to document this change to end users. I suggest to remove this NEWS entry.

of child processes saving memory allocations and copies.
Loading