shared_alloc_mmap.c

/*
   +----------------------------------------------------------------------+
   | ScrewOpcode                                                         |
   +----------------------------------------------------------------------+
   | Copyright (c) 1998-2018 The PHP Group                                |
   +----------------------------------------------------------------------+
   | This source file is subject to version 3.01 of the PHP license,      |
   | that is bundled with this package in the file LICENSE, and is        |
   | available through the world-wide-web at the following url:           |
   | http://www.php.net/license/3_01.txt                                  |
   | If you did not receive a copy of the PHP license and are unable to   |
   | obtain it through the world-wide-web, please send a note to          |
   | license@php.net so we can mail you a copy immediately.               |
   +----------------------------------------------------------------------+
   | Authors: Andi Gutmans <andi@zend.com>                                |
   |          Zeev Suraski <zeev@zend.com>                                |
   |          Stanislav Malyshev <stas@zend.com>                          |
   |          Dmitry Stogov <dmitry@zend.com>                             |
   +----------------------------------------------------------------------+
*/

#include "zend_shared_alloc.h"

#ifdef USE_MMAP

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>

#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
#define MAP_ANONYMOUS MAP_ANON
#endif

static int create_segments(size_t requested_size, zend_shared_segment ***shared_segments_p, int *shared_segments_count, char **error_in)
{
	zend_shared_segment *shared_segment;

	*shared_segments_count = 1;
	*shared_segments_p = (zend_shared_segment **)calloc(1, sizeof(zend_shared_segment) + sizeof(void *));
	if (!*shared_segments_p)
	{
		*error_in = "calloc";
		return ALLOC_FAILURE;
	}
	shared_segment = (zend_shared_segment *)((char *)(*shared_segments_p) + sizeof(void *));
	(*shared_segments_p)[0] = shared_segment;

#ifdef MAP_HUGETLB
	/* Try to allocate huge pages first to reduce dTLB misses.
	 * OS has to be configured properly
	 * (e.g. https://wiki.debian.org/Hugepages#Enabling_HugeTlbPage)
	 * You may verify huge page usage with the following command:
	 * `grep "Huge" /proc/meminfo`
	 */
	shared_segment->p = mmap(0, requested_size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
	if (shared_segment->p != MAP_FAILED)
	{
		shared_segment->pos = 0;
		shared_segment->size = requested_size;

		return ALLOC_SUCCESS;
	}
#endif

	shared_segment->p = mmap(0, requested_size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
	if (shared_segment->p == MAP_FAILED)
	{
		*error_in = "mmap";
		return ALLOC_FAILURE;
	}

	shared_segment->pos = 0;
	shared_segment->size = requested_size;

	return ALLOC_SUCCESS;
}

static int detach_segment(zend_shared_segment *shared_segment)
{
	munmap(shared_segment->p, shared_segment->size);
	return 0;
}

static size_t segment_type_size(void)
{
	return sizeof(zend_shared_segment);
}

zend_shared_memory_handlers zend_alloc_mmap_handlers = {
	create_segments,
	detach_segment,
	segment_type_size};

#endif /* USE_MMAP */