zmalloc.c

/* zmalloc - total amount of allocated memory aware version of malloc()
 *
 * Copyright (c) 2009-2010, Salvatore Sanfilippo <antirez at gmail dot com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdio.h>
#include <stdlib.h>

/* This function provide us access to the original libc free(). This is useful
 * for instance to free results obtained by backtrace_symbols(). We need
 * to define this function before including zmalloc.h that may shadow the
 * free implementation if we use jemalloc or another non standard allocator. */
 //该函数提供了调用原始libc库的free()函数
void zlibc_free(void *ptr) {
    free(ptr);
}

#include <string.h>
#include <pthread.h>
#include "config.h"
#include "zmalloc.h"
#include "atomicvar.h"

//条件编译，决定是否采用多余的PREFIX_SIZE内存记录申请的内存大小
//若HAVE_MALLOC_SIZE，则采用zmalloc_size()获取，反之，通过PREFIX_SIZE大小内存记录的值获取
#ifdef HAVE_MALLOC_SIZE
#define PREFIX_SIZE (0)
#else
#if defined(__sun) || defined(__sparc) || defined(__sparc__)
#define PREFIX_SIZE (sizeof(long long))
#else
#define PREFIX_SIZE (sizeof(size_t))
#endif
#endif

/* Explicitly override malloc/free etc when using tcmalloc. */
//如果使用了tcmalloc用于内存管理，则显式地复写malloc/free相关函数
#if defined(USE_TCMALLOC)
#define malloc(size) tc_malloc(size)
#define calloc(count,size) tc_calloc(count,size)
#define realloc(ptr,size) tc_realloc(ptr,size)
#define free(ptr) tc_free(ptr)
#elif defined(USE_JEMALLOC)
#define malloc(size) je_malloc(size)
#define calloc(count,size) je_calloc(count,size)
#define realloc(ptr,size) je_realloc(ptr,size)
#define free(ptr) je_free(ptr)
#define mallocx(size,flags) je_mallocx(size,flags)
#define dallocx(ptr,flags) je_dallocx(ptr,flags)
#endif

//统计内存分配
#define update_zmalloc_stat_alloc(__n) do { \
    size_t _n = (__n); \
    if (_n&(sizeof(long)-1)) _n += sizeof(long)-(_n&(sizeof(long)-1)); \
    if (zmalloc_thread_safe) { \ //如已启用线程安全模式
        atomicIncr(used_memory,__n,used_memory_mutex); \ //原子更新
    } else { \
        used_memory += _n; \ //否则，直接更新已使用内存
    } \
} while(0)

//统计内存释放
#define update_zmalloc_stat_free(__n) do { \
    size_t _n = (__n); \
    if (_n&(sizeof(long)-1)) _n += sizeof(long)-(_n&(sizeof(long)-1)); \
    if (zmalloc_thread_safe) { \ //如已启用线程安全模式
        atomicDecr(used_memory,__n,used_memory_mutex); \ //原子更新
    } else { \
        used_memory -= _n; \ //否则，直接更新已使用内存
    } \
} while(0)

static size_t used_memory = 0; //已使用的内存大小
static int zmalloc_thread_safe = 0; //线程安全模式
pthread_mutex_t used_memory_mutex = PTHREAD_MUTEX_INITIALIZER; //

//内存溢出异常默认处理方式
static void zmalloc_default_oom(size_t size) {
    fprintf(stderr, "zmalloc: Out of memory trying to allocate %zu bytes\n",
        size); // 打印输出日志
    fflush(stderr); //刷新
    abort(); //中断退出
}
//设置zmalloc_oom_handler初始值
static void (*zmalloc_oom_handler)(size_t) = zmalloc_default_oom;

void *zmalloc(size_t size) {
    //调用malloc函数申请内存空间
    //多申请的PREFIX_SIZE大小内存空间用于记录该段内存大小
    void *ptr = malloc(size+PREFIX_SIZE);
    //如果ptr为NULL，则表示内存分配失败，此时调用zmalloc_oom_handler处理异常
    if (!ptr) zmalloc_oom_handler(size);
    //内存分配统计
#ifdef HAVE_MALLOC_SIZE
    update_zmalloc_stat_alloc(zmalloc_size(ptr));
    return ptr;
#else
    *((size_t*)ptr) = size;
    update_zmalloc_stat_alloc(size+PREFIX_SIZE);
    return (char*)ptr+PREFIX_SIZE;
#endif
}

/* Allocation and free functions that bypass the thread cache
 * and go straight to the allocator arena bins.
 * Currently implemented only for jemalloc. Used for online defragmentation. */
#ifdef HAVE_DEFRAG
void *zmalloc_no_tcache(size_t size) {
    void *ptr = mallocx(size+PREFIX_SIZE, MALLOCX_TCACHE_NONE);
    if (!ptr) zmalloc_oom_handler(size);
    update_zmalloc_stat_alloc(zmalloc_size(ptr));
    return ptr;
}

void zfree_no_tcache(void *ptr) {
    if (ptr == NULL) return;
    update_zmalloc_stat_free(zmalloc_size(ptr));
    dallocx(ptr, MALLOCX_TCACHE_NONE);
}
#endif

//调用系统调用calloc()函数申请内存,逻辑同zmalloc()
void *zcalloc(size_t size) {
    void *ptr = calloc(1, size+PREFIX_SIZE);

    if (!ptr) zmalloc_oom_handler(size);
#ifdef HAVE_MALLOC_SIZE
    update_zmalloc_stat_alloc(zmalloc_size(ptr));
    return ptr;
#else
    *((size_t*)ptr) = size;
    update_zmalloc_stat_alloc(size+PREFIX_SIZE);
    return (char*)ptr+PREFIX_SIZE;
#endif
}
//内存重分配函数
void *zrealloc(void *ptr, size_t size) {
#ifndef HAVE_MALLOC_SIZE
    void *realptr;
#endif
    size_t oldsize;
    void *newptr;
    //若ptr为NULL，则执行内存分配zmalloc()函数
    if (ptr == NULL) return zmalloc(size); 
#ifdef HAVE_MALLOC_SIZE
    oldsize = zmalloc_size(ptr); //原数据内存大小
    newptr = realloc(ptr,size); //调用realloc()重分配内存
    if (!newptr) zmalloc_oom_handler(size); //若newptr为NULL则调用内存溢出异常处理
    //内存使用统计
    update_zmalloc_stat_free(oldsize);
    update_zmalloc_stat_alloc(zmalloc_size(newptr));
    return newptr; 
#else
    realptr = (char*)ptr-PREFIX_SIZE; 
    oldsize = *((size_t*)realptr); //获取原数据内存大小
    newptr = realloc(realptr,size+PREFIX_SIZE);
    if (!newptr) zmalloc_oom_handler(size); //若newptr为NULL则调用内存溢出异常处理
    //内存使用统计
    *((size_t*)newptr) = size;
    update_zmalloc_stat_free(oldsize);
    update_zmalloc_stat_alloc(size);
    return (char*)newptr+PREFIX_SIZE;
#endif
}

/* Provide zmalloc_size() for systems where this function is not provided by
 * malloc itself, given that in that case we store a header with this
 * information as the first bytes of every allocation. */
 //条件编译，根据是否采用多余PREFIX_SIZE大小内存记录申请的空间大小判断
#ifndef HAVE_MALLOC_SIZE
size_t zmalloc_size(void *ptr) {
    void *realptr = (char*)ptr-PREFIX_SIZE;
    size_t size = *((size_t*)realptr);
    /* Assume at least that all the allocations are padded at sizeof(long) by
     * the underlying allocator. */
    if (size&(sizeof(long)-1)) size += sizeof(long)-(size&(sizeof(long)-1));
    return size+PREFIX_SIZE;
}
#endif
//释放内存空间
void zfree(void *ptr) {
#ifndef HAVE_MALLOC_SIZE
    void *realptr;
    size_t oldsize;
#endif

    if (ptr == NULL) return; //若ptr为NULL，则直接返回
    //内存使用情况统计, 调用系统的free()函数
#ifdef HAVE_MALLOC_SIZE
    update_zmalloc_stat_free(zmalloc_size(ptr));
    free(ptr); 
#else
    realptr = (char*)ptr-PREFIX_SIZE;
    oldsize = *((size_t*)realptr);
    update_zmalloc_stat_free(oldsize+PREFIX_SIZE);
    free(realptr);
#endif
}
//字符串拷贝
char *zstrdup(const char *s) {
    size_t l = strlen(s)+1; //计算拷贝需要字符串的长度 + 1('\0')
    char *p = zmalloc(l); //申请内存

    memcpy(p,s,l); //内存拷贝
    return p;
}
//获取已使用的内存
size_t zmalloc_used_memory(void) {
    size_t um;

    if (zmalloc_thread_safe) { //判断是否开启线程安全模式
        atomicGet(used_memory,um,used_memory_mutex); //原子操作
    } else {
        um = used_memory; //直接获取结果
    }
    return um;
}
//设置线程安全模式
void zmalloc_enable_thread_safeness(void) {
    zmalloc_thread_safe = 1;
}
//设置内存溢出异常处理函数
void zmalloc_set_oom_handler(void (*oom_handler)(size_t)) {
    zmalloc_oom_handler = oom_handler;
}

/* Get the RSS information in an OS-specific way.
 *
 * WARNING: the function zmalloc_get_rss() is not designed to be fast
 * and may not be called in the busy loops where Redis tries to release
 * memory expiring or swapping out objects.
 *
 * For this kind of "fast RSS reporting" usages use instead the
 * function RedisEstimateRSS() that is a much faster (and less precise)
 * version of the function. */

#if defined(HAVE_PROC_STAT)
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

size_t zmalloc_get_rss(void) {
    int page = sysconf(_SC_PAGESIZE);
    size_t rss;
    char buf[4096];
    char filename[256];
    int fd, count;
    char *p, *x;

    snprintf(filename,256,"/proc/%d/stat",getpid());
    if ((fd = open(filename,O_RDONLY)) == -1) return 0;
    if (read(fd,buf,4096) <= 0) {
        close(fd);
        return 0;
    }
    close(fd);

    p = buf;
    count = 23; /* RSS is the 24th field in /proc/<pid>/stat */
    while(p && count--) {
        p = strchr(p,' ');
        if (p) p++;
    }
    if (!p) return 0;
    x = strchr(p,' ');
    if (!x) return 0;
    *x = '\0';

    rss = strtoll(p,NULL,10);
    rss *= page;
    return rss;
}
#elif defined(HAVE_TASKINFO)
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/sysctl.h>
#include <mach/task.h>
#include <mach/mach_init.h>

size_t zmalloc_get_rss(void) {
    task_t task = MACH_PORT_NULL;
    struct task_basic_info t_info;
    mach_msg_type_number_t t_info_count = TASK_BASIC_INFO_COUNT;

    if (task_for_pid(current_task(), getpid(), &task) != KERN_SUCCESS)
        return 0;
    task_info(task, TASK_BASIC_INFO, (task_info_t)&t_info, &t_info_count);

    return t_info.resident_size;
}
#else
size_t zmalloc_get_rss(void) {
    /* If we can't get the RSS in an OS-specific way for this system just
     * return the memory usage we estimated in zmalloc()..
     *
     * Fragmentation will appear to be always 1 (no fragmentation)
     * of course... */
    return zmalloc_used_memory();
}
#endif

/* Fragmentation = RSS / allocated-bytes */
float zmalloc_get_fragmentation_ratio(size_t rss) {
    return (float)rss/zmalloc_used_memory();
}

/* Get the sum of the specified field (converted form kb to bytes) in
 * /proc/self/smaps. The field must be specified with trailing ":" as it
 * apperas in the smaps output.
 *
 * If a pid is specified, the information is extracted for such a pid,
 * otherwise if pid is -1 the information is reported is about the
 * current process.
 *
 * Example: zmalloc_get_smap_bytes_by_field("Rss:",-1);
 */
#if defined(HAVE_PROC_SMAPS)
size_t zmalloc_get_smap_bytes_by_field(char *field, long pid) {
    char line[1024];
    size_t bytes = 0;
    int flen = strlen(field);
    FILE *fp;

    if (pid == -1) {
        fp = fopen("/proc/self/smaps","r");
    } else {
        char filename[128];
        snprintf(filename,sizeof(filename),"/proc/%ld/smaps",pid);
        fp = fopen(filename,"r");
    }

    if (!fp) return 0;
    while(fgets(line,sizeof(line),fp) != NULL) {
        if (strncmp(line,field,flen) == 0) {
            char *p = strchr(line,'k');
            if (p) {
                *p = '\0';
                bytes += strtol(line+flen,NULL,10) * 1024;
            }
        }
    }
    fclose(fp);
    return bytes;
}
#else
size_t zmalloc_get_smap_bytes_by_field(char *field, long pid) {
    ((void) field);
    ((void) pid);
    return 0;
}
#endif

size_t zmalloc_get_private_dirty(long pid) {
    return zmalloc_get_smap_bytes_by_field("Private_Dirty:",pid);
}

/* Returns the size of physical memory (RAM) in bytes.
 * It looks ugly, but this is the cleanest way to achive cross platform results.
 * Cleaned up from:
 *
 * http://nadeausoftware.com/articles/2012/09/c_c_tip_how_get_physical_memory_size_system
 *
 * Note that this function:
 * 1) Was released under the following CC attribution license:
 *    http://creativecommons.org/licenses/by/3.0/deed.en_US.
 * 2) Was originally implemented by David Robert Nadeau.
 * 3) Was modified for Redis by Matt Stancliff.
 * 4) This note exists in order to comply with the original license.
 */
size_t zmalloc_get_memory_size(void) {
#if defined(__unix__) || defined(__unix) || defined(unix) || \
    (defined(__APPLE__) && defined(__MACH__))
#if defined(CTL_HW) && (defined(HW_MEMSIZE) || defined(HW_PHYSMEM64))
    int mib[2];
    mib[0] = CTL_HW;
#if defined(HW_MEMSIZE)
    mib[1] = HW_MEMSIZE;            /* OSX. --------------------- */
#elif defined(HW_PHYSMEM64)
    mib[1] = HW_PHYSMEM64;          /* NetBSD, OpenBSD. --------- */
#endif
    int64_t size = 0;               /* 64-bit */
    size_t len = sizeof(size);
    if (sysctl( mib, 2, &size, &len, NULL, 0) == 0)
        return (size_t)size;
    return 0L;          /* Failed? */

#elif defined(_SC_PHYS_PAGES) && defined(_SC_PAGESIZE)
    /* FreeBSD, Linux, OpenBSD, and Solaris. -------------------- */
    return (size_t)sysconf(_SC_PHYS_PAGES) * (size_t)sysconf(_SC_PAGESIZE);

#elif defined(CTL_HW) && (defined(HW_PHYSMEM) || defined(HW_REALMEM))
    /* DragonFly BSD, FreeBSD, NetBSD, OpenBSD, and OSX. -------- */
    int mib[2];
    mib[0] = CTL_HW;
#if defined(HW_REALMEM)
    mib[1] = HW_REALMEM;        /* FreeBSD. ----------------- */
#elif defined(HW_PYSMEM)
    mib[1] = HW_PHYSMEM;        /* Others. ------------------ */
#endif
    unsigned int size = 0;      /* 32-bit */
    size_t len = sizeof(size);
    if (sysctl(mib, 2, &size, &len, NULL, 0) == 0)
        return (size_t)size;
    return 0L;          /* Failed? */
#else
    return 0L;          /* Unknown method to get the data. */
#endif
#else
    return 0L;          /* Unknown OS. */
#endif
}