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klippy: lock process memory to RAM at startup via mlockall #3

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klippy: lock process memory to RAM at startup via mlockall #3

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1 change: 1 addition & 0 deletions klippy/printer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -666,6 +666,7 @@ def main():
logging.getLogger().setLevel(debuglevel)
logging.info("=======================")
logging.info("Starting Klippy...")
util.lock_memory()
git_info = util.get_git_version()
git_vers = git_info["version"]

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20 changes: 20 additions & 0 deletions klippy/util.py
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Expand Up @@ -3,6 +3,8 @@
# Copyright (C) 2016-2020 Kevin O'Connor <kevin@koconnor.net>
#
# This file may be distributed under the terms of the GNU GPLv3 license.
import ctypes
import ctypes.util
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Copilot AI Apr 6, 2026

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ctypes.util is imported but never used. Either remove this import to avoid lint/noise, or use it to resolve the libc path (e.g., via ctypes.util.find_library).

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import ctypes.util

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import fcntl
import json
import logging
Expand All @@ -27,6 +29,24 @@ def fix_sigint():
fix_sigint()


# Lock all current and future memory pages into RAM to prevent swapping
def lock_memory():
MCL_CURRENT = 1
MCL_FUTURE = 2
try:
libc = ctypes.CDLL("libc.so.6", use_errno=True)
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Copilot AI Apr 6, 2026

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Loading libc via the hard-coded name libc.so.6 is glibc-specific and can fail on non-glibc systems (e.g., musl-based containers). Consider using ctypes.util.find_library('c') (with a sensible fallback) or ctypes.CDLL(None) to locate mlockall more portably.

Suggested change
libc = ctypes.CDLL("libc.so.6", use_errno=True)
libc = None
for libname in (None, ctypes.util.find_library("c"), "libc.so.6"):
if libname is None:
candidate = ctypes.CDLL(None, use_errno=True)
else:
try:
candidate = ctypes.CDLL(libname, use_errno=True)
except OSError:
continue
if hasattr(candidate, "mlockall"):
libc = candidate
break
if libc is None:
raise OSError("Unable to locate libc with mlockall")

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result = libc.mlockall(MCL_CURRENT | MCL_FUTURE)
if result != 0:
errno_val = ctypes.get_errno()
raise OSError(errno_val, os.strerror(errno_val))
logging.info(
"Memory locked to RAM (mlockall MCL_CURRENT|MCL_FUTURE):"
" swapping disabled"
)
except Exception as e:
logging.warning("Failed to lock memory: %s", e)


# Set a file-descriptor as non-blocking
def set_nonblock(fd):
fcntl.fcntl(
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