Daniil Tatianin
6c49e5f7dc
Linux wakes up kcompactd threads in order to make more contiguous memory available on the system, it does this by migrating live movable pages (actively modifying live processes' page tables and constantly flooding them with page invalidation IPIs, which can be up to millions per second), which causes the process to become unresponsive for up to seconds or even minutes in some severe cases. In case of sshd, we want to always be able to connect to the system, even if it's under heavy kcompactd load. Introduce an option to protect sshd and its children sessions from being compacted by kcompactd (this works in cojunction with compact_unevictable_allowed = 0). Note that we depend on MCL_ONFAULT being available, which was introduced in linux 4.4. MCL_ONFAULT allows the system to lock pages lazily, thus drastically reducing memory usage of a locked process (without MCL_ONFAULT, every existing mapping in the process is instantly write-faulted).
43 lines
1.3 KiB
C
43 lines
1.3 KiB
C
/*
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* Copyright (c) 2006 Damien Miller <[email protected]>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#ifndef _PORT_LINUX_H
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#define _PORT_LINUX_H
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#ifdef WITH_SELINUX
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int ssh_selinux_enabled(void);
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void ssh_selinux_setup_pty(char *, const char *);
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void ssh_selinux_setup_exec_context(char *);
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void ssh_selinux_change_context(const char *);
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void ssh_selinux_setfscreatecon(const char *);
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#endif
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#ifdef LINUX_OOM_ADJUST
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void oom_adjust_restore(void);
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void oom_adjust_setup(void);
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#endif
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#ifdef LINUX_MEMLOCK_ONFAULT
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void memlock_onfault_setup(void);
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#endif
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#ifdef SYSTEMD_NOTIFY
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void ssh_systemd_notify_ready(void);
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void ssh_systemd_notify_reload(void);
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#endif
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#endif /* ! _PORT_LINUX_H */
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