1 // SPDX-License-Identifier: 0BSD 2 3 /////////////////////////////////////////////////////////////////////////////// 4 // 5 /// \file hardware.h 6 /// \brief Detection of available hardware resources 7 // 8 // Author: Lasse Collin 9 // 10 /////////////////////////////////////////////////////////////////////////////// 11 12 /// Initialize some hardware-specific variables, which are needed by other 13 /// hardware_* functions. 14 extern void hardware_init(void); 15 16 17 /// Set the maximum number of worker threads. 18 /// A special value of UINT32_MAX sets one thread in multi-threaded mode. 19 extern void hardware_threads_set(uint32_t threadlimit); 20 21 /// Get the maximum number of worker threads. 22 extern uint32_t hardware_threads_get(void); 23 24 /// Returns true if multithreaded mode should be used for .xz compression. 25 /// This can be true even if the number of threads is one. 26 extern bool hardware_threads_is_mt(void); 27 28 29 /// Set the memory usage limit. There are separate limits for compression, 30 /// decompression (also includes --list), and multithreaded decompression. 31 /// Any combination of these can be set with a single call to this function. 32 /// Zero indicates resetting the limit back to the defaults. 33 /// The limit can also be set as a percentage of installed RAM; the 34 /// percentage must be in the range [1, 100]. 35 extern void hardware_memlimit_set(uint64_t new_memlimit, 36 bool set_compress, bool set_decompress, bool set_mtdec, 37 bool is_percentage); 38 39 /// Get the current memory usage limit for compression or decompression. 40 /// This is a hard limit that will not be exceeded. This is obeyed in 41 /// both single-threaded and multithreaded modes. 42 extern uint64_t hardware_memlimit_get(enum operation_mode mode); 43 44 /// This returns a system-specific default value if all of the following 45 /// conditions are true: 46 /// 47 /// - An automatic number of threads was requested (--threads=0). 48 /// 49 /// - --memlimit-compress wasn't used or it was reset to the default 50 /// value by setting it to 0. 51 /// 52 /// Otherwise this is identical to hardware_memlimit_get(MODE_COMPRESS). 53 /// 54 /// The idea is to keep automatic thread count reasonable so that too 55 /// high memory usage is avoided and, with 32-bit xz, running out of 56 /// address space is avoided. 57 extern uint64_t hardware_memlimit_mtenc_get(void); 58 59 /// Returns true if the value returned by hardware_memlimit_mtenc_get() is 60 /// a system-specific default value. coder.c uses this to ignore the default 61 /// memlimit in case it's too small even for a single thread in multithreaded 62 /// mode. This way the default limit will never make xz fail or affect the 63 /// compressed output; it will only make xz reduce the number of threads. 64 extern bool hardware_memlimit_mtenc_is_default(void); 65 66 /// Get the current memory usage limit for multithreaded decompression. 67 /// This is only used to reduce the number of threads. This limit can be 68 /// exceeded if the number of threads are reduce to one. Then the value 69 /// from hardware_memlimit_get() will be honored like in single-threaded mode. 70 extern uint64_t hardware_memlimit_mtdec_get(void); 71 72 /// Display the amount of RAM and memory usage limits and exit. 73 tuklib_attr_noreturn 74 extern void hardware_memlimit_show(void); 75