gc.h

// This file is a part of Julia. License is MIT: http://julialang.org/license

/*
  allocation and garbage collection
  . non-moving, precise mark and sweep collector
  . pool-allocates small objects, keeps big objects on a simple list
*/

#ifndef JULIA_GC_H
#define JULIA_GC_H

#include <stdlib.h>
#include <string.h>
#ifndef _MSC_VER
#include <strings.h>
#endif
#include <assert.h>
#include <inttypes.h>
#include "julia.h"
#include "julia_internal.h"
#include "threading.h"
#ifndef _OS_WINDOWS_
#include <sys/mman.h>
#if defined(_OS_DARWIN_) && !defined(MAP_ANONYMOUS)
#define MAP_ANONYMOUS MAP_ANON
#endif
#endif

#ifdef __cplusplus
extern "C" {
#endif

#define GC_PAGE_LG2 14 // log2(size of a page)
#define GC_PAGE_SZ (1 << GC_PAGE_LG2) // 16k
#define GC_PAGE_OFFSET (JL_SMALL_BYTE_ALIGNMENT - (sizeof(jl_taggedvalue_t) % JL_SMALL_BYTE_ALIGNMENT))

// 8G * 32768 = 2^48
// It's really unlikely that we'll actually allocate that much though...
#define REGION_COUNT 32768

#define jl_malloc_tag ((void*)0xdeadaa01)
#define jl_singleton_tag ((void*)0xdeadaa02)

// Used by GC_DEBUG_ENV
typedef struct {
    uint64_t num;
    uint64_t next;

    uint64_t min;
    uint64_t interv;
    uint64_t max;
    unsigned short random[3];
} jl_alloc_num_t;

typedef struct {
    int always_full;
    int wait_for_debugger;
    jl_alloc_num_t pool;
    jl_alloc_num_t other;
    jl_alloc_num_t print;
} jl_gc_debug_env_t;

// This struct must be kept in sync with the Julia type of the same name in base/util.jl
typedef struct {
    int64_t     allocd;
    int64_t     deferred_alloc;
    int64_t     freed;
    uint64_t    malloc;
    uint64_t    realloc;
    uint64_t    poolalloc;
    uint64_t    bigalloc;
    uint64_t    freecall;
    uint64_t    total_time;
    uint64_t    total_allocd;
    uint64_t    since_sweep;
    size_t      interval;
    int         pause;
    int         full_sweep;
} jl_gc_num_t;

// layout for big (>2k) objects

typedef struct _bigval_t {
    struct _bigval_t *next;
    struct _bigval_t **prev; // pointer to the next field of the prev entry
    union {
        size_t sz;
        uintptr_t age : 2;
    };
#ifdef _P64 // Add padding so that the value is 64-byte aligned
    // (8 pointers of 8 bytes each) - (4 other pointers in struct)
    void *_padding[8 - 4];
#else
    // (16 pointers of 4 bytes each) - (4 other pointers in struct)
    void *_padding[16 - 4];
#endif
    //struct jl_taggedvalue_t <>;
    union {
        uintptr_t header;
        struct {
            uintptr_t gc:2;
        } bits;
    };
    // must be 64-byte aligned here, in 32 & 64 bit modes
} bigval_t;

// data structure for tracking malloc'd arrays.

typedef struct _mallocarray_t {
    jl_array_t *a;
    struct _mallocarray_t *next;
} mallocarray_t;

// pool page metadata
typedef struct {
    struct {
        // index of pool that owns this page
        uint16_t pool_n : 8;
        // Whether any cell in the page is marked
        // This bit is set before sweeping iff there's live cells in the page.
        // Note that before marking or after sweeping there can be live
        // (and young) cells in the page for `!has_marked`.
        uint16_t has_marked: 1;
        // Whether any cell was live and young **before sweeping**.
        // For a normal sweep (quick sweep that is NOT preceded by a
        // full sweep) this bit is set iff there are young or newly dead
        // objects in the page and the page needs to be swept.
        //
        // For a full sweep, this bit should be ignored.
        //
        // For a quick sweep preceded by a full sweep. If this bit is set,
        // the page needs to be swept. If this bit is not set, there could
        // still be old dead objects in the page and `nold` and `prev_nold`
        // should be used to determine if the page needs to be swept.
        uint16_t has_young: 1;
    };
    // number of old objects in this page
    uint16_t nold;
    // number of old objects in this page during the previous full sweep
    uint16_t prev_nold;
    // number of free objects in this page.
    // invalid if pool that owns this page is allocating objects from this page.
    uint16_t nfree;
    uint16_t osize; // size of each object in this page
    uint16_t fl_begin_offset; // offset of first free object in this page
    uint16_t fl_end_offset;   // offset of last free object in this page
    uint16_t thread_n;        // thread id of the heap that owns this page
    char *data;
    uint8_t *ages;
} jl_gc_pagemeta_t;

typedef struct {
    char data[GC_PAGE_SZ];
} jl_gc_page_t
#if !defined(_COMPILER_MICROSOFT_) && !(defined(_COMPILER_MINGW_) && defined(_COMPILER_CLANG_))
__attribute__((aligned(GC_PAGE_SZ)))
#endif
;

typedef struct {
    // Page layout:
    //  Newpage freelist: sizeof(void*)
    //  Padding: GC_PAGE_OFFSET - sizeof(void*)
    //  Blocks: osize * n
    //    Tag: sizeof(jl_taggedvalue_t)
    //    Data: <= osize - sizeof(jl_taggedvalue_t)
    jl_gc_page_t *pages; // [pg_cnt]; must be first, to preserve page alignment
    uint32_t *allocmap; // [pg_cnt / 32]
    jl_gc_pagemeta_t *meta; // [pg_cnt]
    int pg_cnt;
    // store a lower bound of the first free page in each region
    int lb;
    // an upper bound of the last non-free page
    int ub;
} region_t;

extern jl_gc_num_t gc_num;
extern region_t regions[REGION_COUNT];
extern bigval_t *big_objects_marked;
extern arraylist_t finalizer_list_marked;
extern arraylist_t to_finalize;
extern int64_t lazy_freed_pages;

STATIC_INLINE bigval_t *bigval_header(jl_taggedvalue_t *o)
{
    return container_of(o, bigval_t, header);
}

// round an address inside a gcpage's data to its beginning
STATIC_INLINE char *gc_page_data(void *x)
{
    return (char*)(((uintptr_t)x >> GC_PAGE_LG2) << GC_PAGE_LG2);
}

STATIC_INLINE jl_taggedvalue_t *page_pfl_beg(jl_gc_pagemeta_t *p)
{
    return (jl_taggedvalue_t*)(p->data + p->fl_begin_offset);
}

STATIC_INLINE jl_taggedvalue_t *page_pfl_end(jl_gc_pagemeta_t *p)
{
    return (jl_taggedvalue_t*)(p->data + p->fl_end_offset);
}

STATIC_INLINE int page_index(region_t *region, void *data)
{
    return (gc_page_data(data) - region->pages->data) / GC_PAGE_SZ;
}

STATIC_INLINE int gc_marked(int bits)
{
    return (bits & GC_MARKED) != 0;
}

STATIC_INLINE int gc_old(int bits)
{
    return (bits & GC_OLD) != 0;
}

STATIC_INLINE uintptr_t gc_ptr_tag(void *v, uintptr_t mask)
{
    return ((uintptr_t)v) & mask;
}

STATIC_INLINE void *gc_ptr_clear_tag(void *v, uintptr_t mask)
{
    return (void*)(((uintptr_t)v) & ~mask);
}

NOINLINE uintptr_t gc_get_stack_ptr(void);

STATIC_INLINE region_t *find_region(void *ptr)
{
    // on 64bit systems we could probably use a single region and remove this loop
    for (int i = 0; i < REGION_COUNT && regions[i].pages; i++) {
        region_t *region = &regions[i];
        char *begin = region->pages->data;
        char *end = begin + region->pg_cnt * sizeof(jl_gc_page_t);
        if ((char*)ptr >= begin && (char*)ptr <= end) {
            return region;
        }
    }
    return NULL;
}

STATIC_INLINE jl_gc_pagemeta_t *page_metadata_(void *data, region_t *r)
{
    assert(r != NULL);
    int pg_idx = page_index(r, (char*)data - GC_PAGE_OFFSET);
    return &r->meta[pg_idx];
}

STATIC_INLINE jl_gc_pagemeta_t *page_metadata(void *data)
{
    return page_metadata_(data, find_region(data));
}

STATIC_INLINE void gc_big_object_unlink(const bigval_t *hdr)
{
    *hdr->prev = hdr->next;
    if (hdr->next) {
        hdr->next->prev = hdr->prev;
    }
}

STATIC_INLINE void gc_big_object_link(bigval_t *hdr, bigval_t **list)
{
    hdr->next = *list;
    hdr->prev = list;
    if (*list)
        (*list)->prev = &hdr->next;
    *list = hdr;
}

void pre_mark(jl_ptls_t ptls);
void gc_mark_object_list(jl_ptls_t ptls, arraylist_t *list, size_t start);
void visit_mark_stack(jl_ptls_t ptls);
void gc_debug_init(void);
void jl_mark_box_caches(jl_ptls_t ptls);

// GC pages

void jl_gc_init_page(void);
NOINLINE void *jl_gc_alloc_page(void);
void jl_gc_free_page(void *p);

// GC debug

#if defined(GC_TIME) || defined(GC_FINAL_STATS)
void gc_settime_premark_end(void);
void gc_settime_postmark_end(void);
#else
#define gc_settime_premark_end()
#define gc_settime_postmark_end()
#endif

#ifdef GC_FINAL_STATS
void gc_final_count_page(size_t pg_cnt);
void gc_final_pause_end(int64_t t0, int64_t tend);
#else
#define gc_final_count_page(pg_cnt)
#define gc_final_pause_end(t0, tend)
#endif

#ifdef GC_TIME
void gc_time_pool_start(void);
void gc_time_count_page(int freedall, int pg_skpd);
void gc_time_pool_end(int sweep_full);

void gc_time_big_start(void);
void gc_time_count_big(int old_bits, int bits);
void gc_time_big_end(void);

void gc_time_mallocd_array_start(void);
void gc_time_count_mallocd_array(int bits);
void gc_time_mallocd_array_end(void);

void gc_time_mark_pause(int64_t t0, int64_t scanned_bytes,
                        int64_t perm_scanned_bytes);
void gc_time_sweep_pause(uint64_t gc_end_t, int64_t actual_allocd,
                         int64_t live_bytes, int64_t estimate_freed,
                         int sweep_full);
#else
#define gc_time_pool_start()
STATIC_INLINE void gc_time_count_page(int freedall, int pg_skpd)
{
    (void)freedall;
    (void)pg_skpd;
}
#define gc_time_pool_end(sweep_full)
#define gc_time_big_start()
STATIC_INLINE void gc_time_count_big(int old_bits, int bits)
{
    (void)old_bits;
    (void)bits;
}
#define gc_time_big_end()
#define gc_time_mallocd_array_start()
STATIC_INLINE void gc_time_count_mallocd_array(int bits)
{
    (void)bits;
}
#define gc_time_mallocd_array_end()
#define gc_time_mark_pause(t0, scanned_bytes, perm_scanned_bytes)
#define gc_time_sweep_pause(gc_end_t, actual_allocd, live_bytes,        \
                            estimate_freed, sweep_full)
#endif

#ifdef MEMFENCE
void gc_verify_tags(void);
#else
static inline void gc_verify_tags(void)
{
}
#endif


#ifdef GC_VERIFY
extern jl_value_t *lostval;
void gc_verify(jl_ptls_t ptls);
void add_lostval_parent(jl_value_t *parent);
#define verify_val(v) do {                                              \
        if (lostval == (jl_value_t*)(v) && (v) != 0) {                  \
            jl_printf(JL_STDOUT,                                        \
                      "Found lostval %p at %s:%d oftype: ",             \
                      (void*)(lostval), __FILE__, __LINE__);            \
            jl_static_show(JL_STDOUT, jl_typeof(v));                    \
            jl_printf(JL_STDOUT, "\n");                                 \
        }                                                               \
    } while(0);

#define verify_parent(ty, obj, slot, args...) do {                      \
        if (gc_ptr_clear_tag(*(void**)(slot), 3) == (void*)lostval &&   \
            (jl_value_t*)(obj) != lostval) {                            \
            jl_printf(JL_STDOUT, "Found parent %p %p at %s:%d\n",       \
                      (void*)(ty), (void*)(obj), __FILE__, __LINE__);   \
            jl_printf(JL_STDOUT, "\tloc %p : ", (void*)(slot));         \
            jl_printf(JL_STDOUT, args);                                 \
            jl_printf(JL_STDOUT, "\n");                                 \
            jl_printf(JL_STDOUT, "\ttype: ");                           \
            jl_static_show(JL_STDOUT, jl_typeof(obj));                  \
            jl_printf(JL_STDOUT, "\n");                                 \
            add_lostval_parent((jl_value_t*)(obj));                     \
        }                                                               \
    } while(0);

#define verify_parent1(ty,obj,slot,arg1) verify_parent(ty,obj,slot,arg1)
#define verify_parent2(ty,obj,slot,arg1,arg2) verify_parent(ty,obj,slot,arg1,arg2)
extern int gc_verifying;
#else
#define gc_verify(ptls)
#define verify_val(v)
#define verify_parent1(ty,obj,slot,arg1)
#define verify_parent2(ty,obj,slot,arg1,arg2)
#define gc_verifying (0)
#endif

#ifdef GC_DEBUG_ENV
JL_DLLEXPORT extern jl_gc_debug_env_t jl_gc_debug_env;
#define gc_sweep_always_full jl_gc_debug_env.always_full
int gc_debug_check_other(void);
int gc_debug_check_pool(void);
void gc_debug_print(void);
void gc_scrub_record_task(jl_task_t *ta);
void gc_scrub(void);
#else
#define gc_sweep_always_full 0
static inline int gc_debug_check_other(void)
{
    return 0;
}
static inline int gc_debug_check_pool(void)
{
    return 0;
}
static inline void gc_debug_print(void)
{
}
static inline void gc_scrub_record_task(jl_task_t *ta)
{
    (void)ta;
}
static inline void gc_scrub(void)
{
}
#endif

#ifdef OBJPROFILE
void objprofile_count(void *ty, int old, int sz);
void objprofile_printall(void);
void objprofile_reset(void);
#else
static inline void objprofile_count(void *ty, int old, int sz)
{
}

static inline void objprofile_printall(void)
{
}

static inline void objprofile_reset(void)
{
}
#endif

#ifdef MEMPROFILE
void gc_stats_all_pool(void);
void gc_stats_big_obj(void);
#else
#define gc_stats_all_pool()
#define gc_stats_big_obj()
#endif

// For debugging
void gc_count_pool(void);

#ifdef __cplusplus
}
#endif

#endif