hardware.c File Reference

Detection of available hardware resources. More...

#include "private.h"

Go to the source code of this file.

Functions
void	hardware_threads_set (uint32_t n)
	Set the maximum number of worker threads. More...
uint32_t	hardware_threads_get (void)
	Get the maximum number of worker threads. More...
void	hardware_memlimit_set (uint64_t new_memlimit, bool set_compress, bool set_decompress, bool is_percentage)
uint64_t	hardware_memlimit_get (enum operation_mode mode)
	Get the current memory usage limit for compression or decompression. More...
static void	memlimit_show (const char *str, uint64_t value)
	Helper for hardware_memlimit_show() to print one human-readable info line. More...
void	hardware_memlimit_show (void)
	Display the amount of RAM and memory usage limits and exit. More...
void	hardware_init (void)

Variables
static uint32_t	threads_max = 1
static uint64_t	memlimit_compress
	Memory usage limit for compression. More...
static uint64_t	memlimit_decompress
	Memory usage limit for decompression. More...
static uint64_t	total_ram
	Total amount of physical RAM. More...

Detailed Description

Detection of available hardware resources.

Definition in file hardware.c.

Function Documentation

hardware_init()

void hardware_init

(

void

)

Initialize some hardware-specific variables, which are needed by other hardware_* functions.

Definition at line 169 of file hardware.c.

{
    // Get the amount of RAM. If we cannot determine it,
    // use the assumption defined by the configure script.
    total_ram = lzma_physmem();
    if (total_ram == 0)
        total_ram = (uint64_t)(ASSUME_RAM) * 1024 * 1024;
 
    // Set the defaults.
    hardware_memlimit_set(0, true, true, false);
    return;
}

References ASSUME_RAM, hardware_memlimit_set(), and total_ram.

Referenced by main().

hardware_memlimit_get()

uint64_t hardware_memlimit_get

(

enum operation_mode

mode

)

Get the current memory usage limit for compression or decompression.

Definition at line 112 of file hardware.c.

{
    // Zero is a special value that indicates the default. Currently
    // the default simply disables the limit. Once there is threading
    // support, this might be a little more complex, because there will
    // probably be a special case where a user asks for "optimal" number
    // of threads instead of a specific number (this might even become
    // the default mode). Each thread may use a significant amount of
    // memory. When there are no memory usage limits set, we need some
    // default soft limit for calculating the "optimal" number of
    // threads.
    const uint64_t memlimit = mode == MODE_COMPRESS
            ? memlimit_compress : memlimit_decompress;
    return memlimit != 0 ? memlimit : UINT64_MAX;
}

References memlimit, memlimit_compress, memlimit_decompress, MODE_COMPRESS, and UINT64_MAX.

Referenced by coder_init(), message_mem_needed(), and parse_indexes().

hardware_memlimit_set()

void hardware_memlimit_set	(	uint64_t	new_memlimit,
		bool	set_compress,
		bool	set_decompress,
		bool	is_percentage
	)

Set the memory usage limit. There are separate limits for compression and decompression (the latter includes also –list), one or both can be set with a single call to this function. Zero indicates resetting the limit back to the defaults. The limit can also be set as a percentage of installed RAM; the percentage must be in the range [1, 100].

Definition at line 62 of file hardware.c.

{
    if (is_percentage) {
        assert(new_memlimit > 0);
        assert(new_memlimit <= 100);
        new_memlimit = (uint32_t)new_memlimit * total_ram / 100;
    }
 
    if (set_compress) {
        memlimit_compress = new_memlimit;
 
#if SIZE_MAX == UINT32_MAX
        // FIXME?
        //
        // When running a 32-bit xz on a system with a lot of RAM and
        // using a percentage-based memory limit, the result can be
        // bigger than the 32-bit address space. Limiting the limit
        // below SIZE_MAX for compression (not decompression) makes
        // xz lower the compression settings (or number of threads)
        // to a level that *might* work. In practice it has worked
        // when using a 64-bit kernel that gives full 4 GiB address
        // space to 32-bit programs. In other situations this might
        // still be too high, like 32-bit kernels that may give much
        // less than 4 GiB to a single application.
        //
        // So this is an ugly hack but I will keep it here while
        // it does more good than bad.
        //
        // Use a value less than SIZE_MAX so that there's some room
        // for the xz program and so on. Don't use 4000 MiB because
        // it could look like someone mixed up base-2 and base-10.
        const uint64_t limit_max = UINT64_C(4020) << 20;
 
        // UINT64_MAX is a special case for the string "max" so
        // that has to be handled specially.
        if (memlimit_compress != UINT64_MAX
                && memlimit_compress > limit_max)
            memlimit_compress = limit_max;
#endif
    }
 
    if (set_decompress)
        memlimit_decompress = new_memlimit;
 
    return;
}

References assert(), memlimit_compress, memlimit_decompress, total_ram, UINT64_C, and UINT64_MAX.

Referenced by hardware_init(), and parse_memlimit().

hardware_memlimit_show()

void hardware_memlimit_show

(

void

)

Display the amount of RAM and memory usage limits and exit.

Definition at line 148 of file hardware.c.

{
    if (opt_robot) {
        printf("%" PRIu64 "\t%" PRIu64 "\t%" PRIu64 "\n", total_ram,
                memlimit_compress, memlimit_decompress);
    } else {
        // TRANSLATORS: Test with "xz --info-memory" to see if
        // the alignment looks nice.
        memlimit_show(_("Total amount of physical memory (RAM): "),
                total_ram);
        memlimit_show(_("Memory usage limit for compression:    "),
                memlimit_compress);
        memlimit_show(_("Memory usage limit for decompression:  "),
                memlimit_decompress);
    }
 
    tuklib_exit(E_SUCCESS, E_ERROR, message_verbosity_get() != V_SILENT);
}

References _, E_ERROR, E_SUCCESS, memlimit_compress, memlimit_decompress, memlimit_show(), message_verbosity_get(), opt_robot, printf(), PRIu64, total_ram, tuklib_exit, and V_SILENT.

Referenced by parse_real().

hardware_threads_get()

uint32_t hardware_threads_get

(

void

)

Get the maximum number of worker threads.

Definition at line 55 of file hardware.c.

{
    return threads_max;
}

References threads_max.

Referenced by coder_init(), coder_normal(), and split_block().

hardware_threads_set()

void hardware_threads_set

(

uint32_t

n

)

Set the maximum number of worker threads.

Definition at line 31 of file hardware.c.

{
    if (n == 0) {
        // Automatic number of threads was requested.
        // If threading support was enabled at build time,
        // use the number of available CPU cores. Otherwise
        // use one thread since disabling threading support
        // omits lzma_cputhreads() from liblzma.
#ifdef MYTHREAD_ENABLED
        threads_max = lzma_cputhreads();
        if (threads_max == 0)
            threads_max = 1;
#else
        threads_max = 1;
#endif
    } else {
        threads_max = n;
    }
 
    return;
}

References n, and threads_max.

Referenced by coder_init(), and parse_real().

memlimit_show()

static void memlimit_show ( const char *  str, uint64_t  value  )

static

Helper for hardware_memlimit_show() to print one human-readable info line.

Definition at line 131 of file hardware.c.

{
    // The memory usage limit is considered to be disabled if value
    // is 0 or UINT64_MAX. This might get a bit more complex once there
    // is threading support. See the comment in hardware_memlimit_get().
    if (value == 0 || value == UINT64_MAX)
        printf("%s %s\n", str, _("Disabled"));
    else
        printf("%s %s MiB (%s B)\n", str,
                uint64_to_str(round_up_to_mib(value), 0),
                uint64_to_str(value, 1));
 
    return;
}

References _, printf(), round_up_to_mib(), cmd_descs_generate::str, UINT64_MAX, uint64_to_str(), and value.

Referenced by hardware_memlimit_show().

Variable Documentation

memlimit_compress

uint64_t memlimit_compress

static

Memory usage limit for compression.

Definition at line 21 of file hardware.c.

Referenced by hardware_memlimit_get(), hardware_memlimit_set(), and hardware_memlimit_show().

memlimit_decompress

uint64_t memlimit_decompress

static

Memory usage limit for decompression.

Definition at line 24 of file hardware.c.

Referenced by hardware_memlimit_get(), hardware_memlimit_set(), and hardware_memlimit_show().

threads_max

uint32_t threads_max = 1

static

Maximum number of worker threads. This can be set with the –threads=NUM command line option.

Definition at line 18 of file hardware.c.

Referenced by hardware_threads_get(), hardware_threads_set(), and init_encoder().

total_ram

uint64_t total_ram

static

Total amount of physical RAM.

Definition at line 27 of file hardware.c.

Referenced by hardware_init(), hardware_memlimit_set(), and hardware_memlimit_show().