54a3a11421
Historically we have not distinguished between kernel wirings and user wirings for accounting purposes. User wirings (via mlock(2)) were subject to a global limit on the number of wired pages, so if large swaths of physical memory were wired by the kernel, as happens with the ZFS ARC among other things, the limit could be exceeded, causing user wirings to fail. The change adds a new counter, v_user_wire_count, which counts the number of virtual pages wired by user processes via mlock(2) and mlockall(2). Only user-wired pages are subject to the system-wide limit which helps provide some safety against deadlocks. In particular, while sources of kernel wirings typically support some backpressure mechanism, there is no way to reclaim user-wired pages shorting of killing the wiring process. The limit is exported as vm.max_user_wired, renamed from vm.max_wired, and changed from u_int to u_long. The choice to count virtual user-wired pages rather than physical pages was done for simplicity. There are mechanisms that can cause user-wired mappings to be destroyed while maintaining a wiring of the backing physical page; these make it difficult to accurately track user wirings at the physical page layer. The change also closes some holes which allowed user wirings to succeed even when they would cause the system limit to be exceeded. For instance, mmap() may now fail with ENOMEM in a process that has called mlockall(MCL_FUTURE) if the new mapping would cause the user wiring limit to be exceeded. Note that bhyve -S is subject to the user wiring limit, which defaults to 1/3 of physical RAM. Users that wish to exceed the limit must tune vm.max_user_wired. Reviewed by: kib, ngie (mlock() test changes) Tested by: pho (earlier version) MFC after: 45 days Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D19908
112 lines
3.6 KiB
C
112 lines
3.6 KiB
C
/*-
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* SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
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*
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* The Mach Operating System project at Carnegie-Mellon University.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)vm_pageout.h 8.2 (Berkeley) 1/12/94
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*
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*
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* Copyright (c) 1987, 1990 Carnegie-Mellon University.
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* All rights reserved.
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*
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* Author: Avadis Tevanian, Jr.
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*
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* Permission to use, copy, modify and distribute this software and
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* its documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
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* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*
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* $FreeBSD$
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*/
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#ifndef _VM_VM_PAGEOUT_H_
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#define _VM_VM_PAGEOUT_H_
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#ifdef _KERNEL
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/*
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* Header file for pageout daemon.
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*/
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/*
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* Exported data structures.
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*/
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extern u_long vm_page_max_user_wired;
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extern int vm_pageout_page_count;
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#define VM_OOM_MEM 1
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#define VM_OOM_SWAPZ 2
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/*
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* vm_lowmem flags.
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*/
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#define VM_LOW_KMEM 0x01
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#define VM_LOW_PAGES 0x02
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/*
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* Exported routines.
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*/
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/*
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* Signal pageout-daemon and wait for it.
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*/
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void vm_wait(vm_object_t obj);
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void vm_waitpfault(struct domainset *);
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void vm_wait_domain(int domain);
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void vm_wait_min(void);
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void vm_wait_severe(void);
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int vm_pageout_flush(vm_page_t *, int, int, int, int *, boolean_t *);
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void vm_pageout_oom(int shortage);
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void vm_swapout_run(void);
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void vm_swapout_run_idle(void);
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#endif /* _KERNEL */
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#endif /* _VM_VM_PAGEOUT_H_ */
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