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 */ 87