1/*
2 * Copyright (c) 2013 Apple Computer, Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28
29#ifndef _SYS_KERN_OVERRIDES_H
30#define _SYS_KERN_OVERRIDES_H
31
32#include <sys/cdefs.h>
33#include <sys/param.h>
34#include <sys/types.h>
35#include <stdint.h>
36
37__BEGIN_DECLS
38
39/*
40 * system_override() system call
41 *
42 * The system_override() syscall is used to modify some kernel performance mechanisms.
43 * The system call needs a special entitlement and should be used with extreme caution.
44 * A misuse of this syscall could lead to severe performance and battery life issues.
45 *
46 * The caller needs to specify the mask for the specific mechanisms to modify and a
47 * timeout. The implementation of this system call blocks the thread in the syscall
48 * for the duration specified in the call. Blocking a thread in the system call allows
49 * the kernel to revert the modification in case the calling process dies. It also
50 * makes the change of behavior extremely obvious due to the backtrace of the calling
51 * thread.
52 *
53 * Multiple agents are allowed to call this interface at the same time. The behavior
54 * change is effective from the time the first call is made (for a specific mechanism)
55 * until the longest timeout specified by any agent. If the caller wishes to disable
56 * the behavior change caused by itself, it can call the same interface with the
57 * SYS_OVERRIDE_DISABLE flag and the mechanism mask from another thread in the same
58 * process. Note that this does not break out the original thread from the block
59 * immediately. It simply undoes the mechanism change underneath.
60 *
61 * The currently supported overrides are:
62 * - SYS_OVERRIDE_IO_THROTTLE: Modifies I/O throttling behavior
63 * - SYS_OVERRIDE_CPU_THROTTLE: Modifies background stepper throttling mechanism
64 * - SYS_OVERRIDE_FAST_JETSAM: Modifies jetsam behavior to use aggressive parallel jetsam
65 *
66 */
67
68/* System Overrides Flags */
69#define SYS_OVERRIDE_DISABLE (~(~0ull >> 1))
70#define SYS_OVERRIDE_IO_THROTTLE 0x1
71#define SYS_OVERRIDE_CPU_THROTTLE 0x2
72#define SYS_OVERRIDE_FAST_JETSAM 0x4
73
74#define SYS_OVERRIDE_FLAGS_MASK (SYS_OVERRIDE_DISABLE | SYS_OVERRIDE_IO_THROTTLE | SYS_OVERRIDE_CPU_THROTTLE | SYS_OVERRIDE_FAST_JETSAM)
75
76#ifdef BSD_KERNEL_PRIVATE
77void init_system_override(void);
78#endif
79
80#ifndef KERNEL
81int system_override(uint64_t timeout, uint64_t flags);
82#endif
83
84__END_DECLS
85
86#endif /*_SYS_KERN_OVERRIDES_H */
87