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gh-121313: Limit the reading size from pipes to their default buffer size on Unix systems #121315

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merged 19 commits into from
Aug 31, 2024
Merged

gh-121313: Limit the reading size from pipes to their default buffer size on Unix systems #121315

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108e65b
Add clean code
aplaikner Jul 3, 2024
37ca606
Fix linting error & sysconf unsupported error
aplaikner Jul 3, 2024
df4f307
Merge branch 'main' into feature-smaller-pipe-buffer-pull-request
aplaikner Jul 3, 2024
89936c2
📜🤖 Added by blurb_it.
blurb-it[bot] Jul 3, 2024
31c65b4
Fix news
aplaikner Jul 3, 2024
0a4e4a3
Make page size non static
aplaikner Jul 3, 2024
7afde51
Merge branch 'main' into feature-smaller-pipe-buffer-pull-request
aplaikner Jul 3, 2024
8d9b16e
Merge branch 'main' into feature-smaller-pipe-buffer-pull-request
aplaikner Jul 3, 2024
e6c64fe
Remove redundant call to pymin
aplaikner Jul 4, 2024
936b601
Shift pipe check to connection.py _recv
aplaikner Jul 5, 2024
49d8adb
Make pipe size dependant on systems page size
aplaikner Jul 5, 2024
43e19dd
Only execute fstat in case reading size is bigger than default pipe size
aplaikner Jul 5, 2024
b0b86e5
Update news message
aplaikner Jul 7, 2024
2b6ff24
Make imports order alphabetical
aplaikner Jul 7, 2024
e726f51
Shift calculation for pipe size to existing if _winapi check
aplaikner Jul 7, 2024
59cff4d
Fix linting error
aplaikner Jul 7, 2024
da10f8e
Merge branch 'main' into feature-smaller-pipe-buffer-pull-request
aplaikner Jul 7, 2024
94d4c4a
Create constant for default number of pages per pipe
aplaikner Jul 7, 2024
52606d1
Merge branch 'main' into feature-smaller-pipe-buffer-pull-request
aplaikner Jul 29, 2024
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12 changes: 11 additions & 1 deletion Lib/multiprocessing/connection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
import time
import tempfile
import itertools
import stat
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@cmaloney cmaloney Jul 5, 2024 •
edited
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Personal nitpick, PEP-8 doesn't seem to specify (https://peps.python.org/pep-0008/#imports), but I like imports to be alphabetical. itertools, time, and tempfile which were already in the code just above this are also out of order (although time and tempfile only slightly). Rest are in order. Not sure if it matters for Python core developer acceptance

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Done



from . import util
Expand Down Expand Up @@ -391,8 +392,17 @@ def _recv(self, size, read=_read):
buf = io.BytesIO()
handle = self._handle
remaining = size
is_pipe = False
page_size = 0
if not _winapi:
page_size = os.sysconf(os.sysconf_names['SC_PAGESIZE'])
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Rather than do the if not _winapi here, which has to be run/interpreted per _recv call, can you add the "calculate max size for a fifo" like https://github.com/python/cpython/blob/main/Lib/multiprocessing/connection.py#L370-L379 does to choose/define the standard read function? Code here will still need to do the min logic + "is this a fifo", but at least reduces overhead work a little bit further.

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I've shifted fetching the base page size and calculating the default pipe size to the existing if _winapi block above. Is this what you meant?

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Yep, looking good

if size > 16 * page_size:
mode = os.fstat(handle).st_mode
is_pipe = stat.S_ISFIFO(mode)
limit = 16 * page_size if is_pipe else remaining
while remaining > 0:
chunk = read(handle, remaining)
to_read = min(limit, remaining)
chunk = read(handle, to_read)
n = len(chunk)
if n == 0:
if remaining == size:
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/C API/2024-07-03-10-11-53.gh-issue-121313.D7gARW.rst
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@@ -0,0 +1 @@
Limit reading size in os.read for pipes to default pipe size in order to avoid memory overallocation
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This should be updated from os.read -> multiprocessing to follow the logic location change.

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Done

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