* Copyright (c) 2013 Apple Computer, Inc. All rights reserved.
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
* system_override() system call
* The system_override() syscall is used to modify some kernel performance mechanisms.
* The system call needs a special entitlement and should be used with extreme caution.
* A misuse of this syscall could lead to severe performance and battery life issues.
* The caller needs to specify the mask for the specific mechanisms to modify and a
* timeout. The implementation of this system call blocks the thread in the syscall
* for the duration specified in the call. Blocking a thread in the system call allows
* the kernel to revert the modification in case the calling process dies. It also
* makes the change of behavior extremely obvious due to the backtrace of the calling
* Multiple agents are allowed to call this interface at the same time. The behavior
* change is effective from the time the first call is made (for a specific mechanism)
* until the longest timeout specified by any agent. If the caller wishes to disable
* the behavior change caused by itself, it can call the same interface with the
* SYS_OVERRIDE_DISABLE flag and the mechanism mask from another thread in the same
* process. Note that this does not break out the original thread from the block
* immediately. It simply undoes the mechanism change underneath.
* The currently supported overrides are:
* - SYS_OVERRIDE_IO_THROTTLE: Modifies I/O throttling behavior
* - SYS_OVERRIDE_CPU_THROTTLE: Modifies background stepper throttling mechanism
* - SYS_OVERRIDE_FAST_JETSAM: Modifies jetsam behavior to use aggressive parallel jetsam
/* System Overrides Flags */
#define SYS_OVERRIDE_DISABLE (~(~0ull >> 1))
#define SYS_OVERRIDE_IO_THROTTLE 0x1
#define SYS_OVERRIDE_CPU_THROTTLE 0x2
#define SYS_OVERRIDE_FAST_JETSAM 0x4
#define SYS_OVERRIDE_FLAGS_MASK (SYS_OVERRIDE_DISABLE | SYS_OVERRIDE_IO_THROTTLE | SYS_OVERRIDE_CPU_THROTTLE | SYS_OVERRIDE_FAST_JETSAM)
int system_override(uint64_t timeout, uint64_t flags);
#endif /*_SYS_KERN_OVERRIDES_H */