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