bsd/sys/kern_overrides.h

   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
  77 void init_system_override(void);
  78 #endif
  79
  80 #ifndef KERNEL
  81 int system_override(uint64_t timeout, uint64_t flags);
  82 #endif
  83
  84 __END_DECLS
  85
  86 #endif /*_SYS_KERN_OVERRIDES_H */