diff options
| -rw-r--r-- | src/malloc/mallocng/README.mallocng | 13 | ||||
| -rw-r--r-- | src/malloc/mallocng/aligned_alloc.c | 57 | ||||
| -rw-r--r-- | src/malloc/mallocng/free.c | 143 | ||||
| -rw-r--r-- | src/malloc/mallocng/malloc.c | 387 | ||||
| -rw-r--r-- | src/malloc/mallocng/malloc_usable_size.c | 12 | ||||
| -rw-r--r-- | src/malloc/mallocng/meta.h | 288 | ||||
| -rw-r--r-- | src/malloc/mallocng/realloc.c | 51 |
7 files changed, 938 insertions, 13 deletions
diff --git a/src/malloc/mallocng/README.mallocng b/src/malloc/mallocng/README.mallocng deleted file mode 100644 index da32bf06..00000000 --- a/src/malloc/mallocng/README.mallocng +++ /dev/null @@ -1,13 +0,0 @@ -This directory is a skeleton for upcoming merge of musl's new malloc -implementation, mallocng. To use it, drop in copies of or symlinks to -the following files from mallocng: - -- meta.h -- malloc.c -- realloc.c -- free.c -- aligned_alloc.c -- malloc_usable_size.c - -and build with make variable MALLOC_DIR=mallocng in config.mak or on -make command line. diff --git a/src/malloc/mallocng/aligned_alloc.c b/src/malloc/mallocng/aligned_alloc.c new file mode 100644 index 00000000..34116896 --- /dev/null +++ b/src/malloc/mallocng/aligned_alloc.c @@ -0,0 +1,57 @@ +#include <stdlib.h> +#include <errno.h> +#include "meta.h" + +void *aligned_alloc(size_t align, size_t len) +{ + if ((align & -align) != align) { + errno = EINVAL; + return 0; + } + + if (len > SIZE_MAX - align || align >= (1ULL<<31)*UNIT) { + errno = ENOMEM; + return 0; + } + + if (DISABLE_ALIGNED_ALLOC) { + errno = ENOMEM; + return 0; + } + + if (align <= UNIT) align = UNIT; + + unsigned char *p = malloc(len + align - UNIT); + struct meta *g = get_meta(p); + int idx = get_slot_index(p); + size_t stride = get_stride(g); + unsigned char *start = g->mem->storage + stride*idx; + unsigned char *end = g->mem->storage + stride*(idx+1) - IB; + size_t adj = -(uintptr_t)p & (align-1); + + if (!adj) { + set_size(p, end, len); + return p; + } + p += adj; + uint32_t offset = (size_t)(p-g->mem->storage)/UNIT; + if (offset <= 0xffff) { + *(uint16_t *)(p-2) = offset; + p[-4] = 0; + } else { + // use a 32-bit offset if 16-bit doesn't fit. for this, + // 16-bit field must be zero, [-4] byte nonzero. + *(uint16_t *)(p-2) = 0; + *(uint32_t *)(p-8) = offset; + p[-4] = 1; + } + p[-3] = idx; + set_size(p, end, len); + // store offset to aligned enframing. this facilitates cycling + // offset and also iteration of heap for debugging/measurement. + // for extreme overalignment it won't fit but these are classless + // allocations anyway. + *(uint16_t *)(start - 2) = (size_t)(p-start)/UNIT; + start[-3] = 7<<5; + return p; +} diff --git a/src/malloc/mallocng/free.c b/src/malloc/mallocng/free.c new file mode 100644 index 00000000..40745f97 --- /dev/null +++ b/src/malloc/mallocng/free.c @@ -0,0 +1,143 @@ +#define _BSD_SOURCE +#include <stdlib.h> +#include <sys/mman.h> + +#include "meta.h" + +struct mapinfo { + void *base; + size_t len; +}; + +static struct mapinfo nontrivial_free(struct meta *, int); + +static struct mapinfo free_group(struct meta *g) +{ + struct mapinfo mi = { 0 }; + int sc = g->sizeclass; + if (sc < 48) { + ctx.usage_by_class[sc] -= g->last_idx+1; + } + if (g->maplen) { + step_seq(); + record_seq(sc); + mi.base = g->mem; + mi.len = g->maplen*4096UL; + } else { + void *p = g->mem; + struct meta *m = get_meta(p); + int idx = get_slot_index(p); + g->mem->meta = 0; + // not checking size/reserved here; it's intentionally invalid + mi = nontrivial_free(m, idx); + } + free_meta(g); + return mi; +} + +static int okay_to_free(struct meta *g) +{ + int sc = g->sizeclass; + + if (!g->freeable) return 0; + + // always free individual mmaps not suitable for reuse + if (sc >= 48 || get_stride(g) < UNIT*size_classes[sc]) + return 1; + + // always free groups allocated inside another group's slot + // since recreating them should not be expensive and they + // might be blocking freeing of a much larger group. + if (!g->maplen) return 1; + + // if there is another non-full group, free this one to + // consolidate future allocations, reduce fragmentation. + if (g->next != g) return 1; + + // free any group in a size class that's not bouncing + if (!is_bouncing(sc)) return 1; + + size_t cnt = g->last_idx+1; + size_t usage = ctx.usage_by_class[sc]; + + // if usage is high enough that a larger count should be + // used, free the low-count group so a new one will be made. + if (9*cnt <= usage && cnt < 20) + return 1; + + // otherwise, keep the last group in a bouncing class. + return 0; +} + +static struct mapinfo nontrivial_free(struct meta *g, int i) +{ + uint32_t self = 1u<<i; + int sc = g->sizeclass; + uint32_t mask = g->freed_mask | g->avail_mask; + + if (mask+self == (2u<<g->last_idx)-1 && okay_to_free(g)) { + // any multi-slot group is necessarily on an active list + // here, but single-slot groups might or might not be. + if (g->next) { + assert(sc < 48); + int activate_new = (ctx.active[sc]==g); + dequeue(&ctx.active[sc], g); + if (activate_new && ctx.active[sc]) + activate_group(ctx.active[sc]); + } + return free_group(g); + } else if (!mask) { + assert(sc < 48); + // might still be active if there were no allocations + // after last available slot was taken. + if (ctx.active[sc] != g) { + queue(&ctx.active[sc], g); + } + } + a_or(&g->freed_mask, self); + return (struct mapinfo){ 0 }; +} + +void free(void *p) +{ + if (!p) return; + + struct meta *g = get_meta(p); + int idx = get_slot_index(p); + size_t stride = get_stride(g); + unsigned char *start = g->mem->storage + stride*idx; + unsigned char *end = start + stride - IB; + get_nominal_size(p, end); + uint32_t self = 1u<<idx, all = (2u<<g->last_idx)-1; + ((unsigned char *)p)[-3] = 255; + // invalidate offset to group header, and cycle offset of + // used region within slot if current offset is zero. + *(uint16_t *)((char *)p-2) = 0; + + // release any whole pages contained in the slot to be freed + // unless it's a single-slot group that will be unmapped. + if (((uintptr_t)(start-1) ^ (uintptr_t)end) >= 2*PGSZ && g->last_idx) { + unsigned char *base = start + (-(uintptr_t)start & (PGSZ-1)); + size_t len = (end-base) & -PGSZ; + if (len) madvise(base, len, MADV_FREE); + } + + // atomic free without locking if this is neither first or last slot + for (;;) { + uint32_t freed = g->freed_mask; + uint32_t avail = g->avail_mask; + uint32_t mask = freed | avail; + assert(!(mask&self)); + if (!freed || mask+self==all) break; + if (!MT) + g->freed_mask = freed+self; + else if (a_cas(&g->freed_mask, freed, freed+self)!=freed) + continue; + return; + } + + wrlock(); + struct mapinfo mi = nontrivial_free(g, idx); + unlock(); + if (mi.len) munmap(mi.base, mi.len); +} diff --git a/src/malloc/mallocng/malloc.c b/src/malloc/mallocng/malloc.c new file mode 100644 index 00000000..d695ab8e --- /dev/null +++ b/src/malloc/mallocng/malloc.c @@ -0,0 +1,387 @@ +#include <stdlib.h> +#include <stdint.h> +#include <limits.h> +#include <string.h> +#include <sys/mman.h> +#include <errno.h> + +#include "meta.h" + +LOCK_OBJ_DEF; + +const uint16_t size_classes[] = { + 1, 2, 3, 4, 5, 6, 7, 8, + 9, 10, 12, 15, + 18, 20, 25, 31, + 36, 42, 50, 63, + 72, 84, 102, 127, + 146, 170, 204, 255, + 292, 340, 409, 511, + 584, 682, 818, 1023, + 1169, 1364, 1637, 2047, + 2340, 2730, 3276, 4095, + 4680, 5460, 6552, 8191, +}; + +static const uint8_t small_cnt_tab[][3] = { + { 30, 30, 30 }, + { 31, 15, 15 }, + { 20, 10, 10 }, + { 31, 15, 7 }, + { 25, 12, 6 }, + { 21, 10, 5 }, + { 18, 8, 4 }, + { 31, 15, 7 }, + { 28, 14, 6 }, +}; + +static const uint8_t med_cnt_tab[4] = { 28, 24, 20, 32 }; + +struct malloc_context ctx = { 0 }; + +struct meta *alloc_meta(void) +{ + struct meta *m; + unsigned char *p; + if (!ctx.init_done) { +#ifndef PAGESIZE + ctx.pagesize = get_page_size(); +#endif + ctx.secret = get_random_secret(); + ctx.init_done = 1; + } + size_t pagesize = PGSZ; + if (pagesize < 4096) pagesize = 4096; + if ((m = dequeue_head(&ctx.free_meta_head))) return m; + if (!ctx.avail_meta_count) { + int need_unprotect = 1; + if (!ctx.avail_meta_area_count && ctx.brk!=-1) { + uintptr_t new = ctx.brk + pagesize; + int need_guard = 0; + if (!ctx.brk) { + need_guard = 1; + ctx.brk = brk(0); + // some ancient kernels returned _ebss + // instead of next page as initial brk. + ctx.brk += -ctx.brk & (pagesize-1); + new = ctx.brk + 2*pagesize; + } + if (brk(new) != new) { + ctx.brk = -1; + } else { + if (need_guard) mmap((void *)ctx.brk, pagesize, + PROT_NONE, MAP_ANON|MAP_PRIVATE|MAP_FIXED, -1, 0); + ctx.brk = new; + ctx.avail_meta_areas = (void *)(new - pagesize); + ctx.avail_meta_area_count = pagesize>>12; + need_unprotect = 0; + } + } + if (!ctx.avail_meta_area_count) { + size_t n = 2UL << ctx.meta_alloc_shift; + p = mmap(0, n*pagesize, PROT_NONE, + MAP_PRIVATE|MAP_ANON, -1, 0); + if (p==MAP_FAILED) return 0; + ctx.avail_meta_areas = p + pagesize; + ctx.avail_meta_area_count = (n-1)*(pagesize>>12); + ctx.meta_alloc_shift++; + } + p = ctx.avail_meta_areas; + if ((uintptr_t)p & (pagesize-1)) need_unprotect = 0; + if (need_unprotect) + if (mprotect(p, pagesize, PROT_READ|PROT_WRITE) + && errno != ENOSYS) + return 0; + ctx.avail_meta_area_count--; + ctx.avail_meta_areas = p + 4096; + if (ctx.meta_area_tail) { + ctx.meta_area_tail->next = (void *)p; + } else { + ctx.meta_area_head = (void *)p; + } + ctx.meta_area_tail = (void *)p; + ctx.meta_area_tail->check = ctx.secret; + ctx.avail_meta_count = ctx.meta_area_tail->nslots + = (4096-sizeof(struct meta_area))/sizeof *m; + ctx.avail_meta = ctx.meta_area_tail->slots; + } + ctx.avail_meta_count--; + m = ctx.avail_meta++; + m->prev = m->next = 0; + return m; +} + +static uint32_t try_avail(struct meta **pm) +{ + struct meta *m = *pm; + uint32_t first; + if (!m) return 0; + uint32_t mask = m->avail_mask; + if (!mask) { + if (!m) return 0; + if (!m->freed_mask) { + dequeue(pm, m); + m = *pm; + if (!m) return 0; + } else { + m = m->next; + *pm = m; + } + + mask = m->freed_mask; + + // skip fully-free group unless it's the only one + // or it's a permanently non-freeable group + if (mask == (2u<<m->last_idx)-1 && m->freeable) { + m = m->next; + *pm = m; + mask = m->freed_mask; + } + + // activate more slots in a not-fully-active group + // if needed, but only as a last resort. prefer using + // any other group with free slots. this avoids + // touching & dirtying as-yet-unused pages. + if (!(mask & ((2u<<m->mem->active_idx)-1))) { + if (m->next != m) { + m = m->next; + *pm = m; + } else { + int cnt = m->mem->active_idx + 2; + int size = size_classes[m->sizeclass]*UNIT; + int span = UNIT + size*cnt; + // activate up to next 4k boundary + while ((span^(span+size-1)) < 4096) { + cnt++; + span += size; + } + if (cnt > m->last_idx+1) + cnt = m->last_idx+1; + m->mem->active_idx = cnt-1; + } + } + mask = activate_group(m); + assert(mask); + decay_bounces(m->sizeclass); + } + first = mask&-mask; + m->avail_mask = mask-first; + return first; +} + +static int alloc_slot(int, size_t); + +static struct meta *alloc_group(int sc, size_t req) +{ + size_t size = UNIT*size_classes[sc]; + int i = 0, cnt; + unsigned char *p; + struct meta *m = alloc_meta(); + if (!m) return 0; + size_t usage = ctx.usage_by_class[sc]; + size_t pagesize = PGSZ; + int active_idx; + if (sc < 9) { + while (i<2 && 4*small_cnt_tab[sc][i] > usage) + i++; + cnt = small_cnt_tab[sc][i]; + } else { + // lookup max number of slots fitting in power-of-two size + // from a table, along with number of factors of two we + // can divide out without a remainder or reaching 1. + cnt = med_cnt_tab[sc&3]; + + // reduce cnt to avoid excessive eagar allocation. + while (!(cnt&1) && 4*cnt > usage) + cnt >>= 1; + + // data structures don't support groups whose slot offsets + // in units don't fit in 16 bits. + while (size*cnt >= 65536*UNIT) + cnt >>= 1; + } + + // If we selected a count of 1 above but it's not sufficient to use + // mmap, increase to 2. Then it might be; if not it will nest. + if (cnt==1 && size*cnt+UNIT <= pagesize/2) cnt = 2; + + // All choices of size*cnt are "just below" a power of two, so anything + // larger than half the page size should be allocated as whole pages. + if (size*cnt+UNIT > pagesize/2) { + // check/update bounce counter to start/increase retention + // of freed maps, and inhibit use of low-count, odd-size + // small mappings and single-slot groups if activated. + int nosmall = is_bouncing(sc); + account_bounce(sc); + step_seq(); + + // since the following count reduction opportunities have + // an absolute memory usage cost, don't overdo them. count + // coarse usage as part of usage. + if (!(sc&1) && sc<32) usage += ctx.usage_by_class[sc+1]; + + // try to drop to a lower count if the one found above + // increases usage by more than 25%. these reduced counts + // roughly fill an integral number of pages, just not a + // power of two, limiting amount of unusable space. + if (4*cnt > usage && !nosmall) { + if (0); + else if ((sc&3)==1 && size*cnt>8*pagesize) cnt = 2; + else if ((sc&3)==2 && size*cnt>4*pagesize) cnt = 3; + else if ((sc&3)==0 && size*cnt>8*pagesize) cnt = 3; + else if ((sc&3)==0 && size*cnt>2*pagesize) cnt = 5; + } + size_t needed = size*cnt + UNIT; + needed += -needed & (pagesize-1); + + // produce an individually-mmapped allocation if usage is low, + // bounce counter hasn't triggered, and either it saves memory + // or it avoids eagar slot allocation without wasting too much. + if (!nosmall && cnt<=7) { + req += IB + UNIT; + req += -req & (pagesize-1); + if (req<size+UNIT || (req>=4*pagesize && 2*cnt>usage)) { + cnt = 1; + needed = req; + } + } + + p = mmap(0, needed, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); + if (p==MAP_FAILED) { + free_meta(m); + return 0; + } + m->maplen = needed>>12; + ctx.mmap_counter++; + active_idx = (4096-UNIT)/size-1; + if (active_idx > cnt-1) active_idx = cnt-1; + if (active_idx < 0) active_idx = 0; + } else { + int j = size_to_class(UNIT+cnt*size-IB); + int idx = alloc_slot(j, UNIT+cnt*size-IB); + if (idx < 0) { + free_meta(m); + return 0; + } + struct meta *g = ctx.active[j]; + p = enframe(g, idx, UNIT*size_classes[j]-IB, ctx.mmap_counter); + m->maplen = 0; + p[-3] = (p[-3]&31) | (6<<5); + for (int i=0; i<=cnt; i++) + p[UNIT+i*size-4] = 0; + active_idx = cnt-1; + } + ctx.usage_by_class[sc] += cnt; + m->avail_mask = (2u<<active_idx)-1; + m->freed_mask = (2u<<(cnt-1))-1 - m->avail_mask; + m->mem = (void *)p; + m->mem->meta = m; + m->mem->active_idx = active_idx; + m->last_idx = cnt-1; + m->freeable = 1; + m->sizeclass = sc; + return m; +} + +static int alloc_slot(int sc, size_t req) +{ + uint32_t first = try_avail(&ctx.active[sc]); + if (first) return a_ctz_32(first); + + struct meta *g = alloc_group(sc, req); + if (!g) return -1; + + g->avail_mask--; + queue(&ctx.active[sc], g); + return 0; +} + +void *malloc(size_t n) +{ + if (size_overflows(n)) return 0; + struct meta *g; + uint32_t mask, first; + int sc; + int idx; + int ctr; + + if (n >= MMAP_THRESHOLD) { + size_t needed = n + IB + UNIT; + void *p = mmap(0, needed, PROT_READ|PROT_WRITE, + MAP_PRIVATE|MAP_ANON, -1, 0); + if (p==MAP_FAILED) return 0; + wrlock(); + step_seq(); + g = alloc_meta(); + if (!g) { + unlock(); + munmap(p, needed); + return 0; + } + g->mem = p; + g->mem->meta = g; + g->last_idx = 0; + g->freeable = 1; + g->sizeclass = 63; + g->maplen = (needed+4095)/4096; + g->avail_mask = g->freed_mask = 0; + // use a global counter to cycle offset in + // individually-mmapped allocations. + ctx.mmap_counter++; + idx = 0; + goto success; + } + + sc = size_to_class(n); + + rdlock(); + g = ctx.active[sc]; + + // use coarse size classes initially when there are not yet + // any groups of desired size. this allows counts of 2 or 3 + // to be allocated at first rather than having to start with + // 7 or 5, the min counts for even size classes. + if (!g && sc>=4 && sc<32 && sc!=6 && !(sc&1) && !ctx.usage_by_class[sc]) { + size_t usage = ctx.usage_by_class[sc|1]; + // if a new group may be allocated, count it toward + // usage in deciding if we can use coarse class. + if (!ctx.active[sc|1] || (!ctx.active[sc|1]->avail_mask + && !ctx.active[sc|1]->freed_mask)) + usage += 3; + if (usage <= 12) + sc |= 1; + g = ctx.active[sc]; + } + + for (;;) { + mask = g ? g->avail_mask : 0; + first = mask&-mask; + if (!first) break; + if (RDLOCK_IS_EXCLUSIVE || !MT) + g->avail_mask = mask-first; + else if (a_cas(&g->avail_mask, mask, mask-first)!=mask) + continue; + idx = a_ctz_32(first); + goto success; + } + upgradelock(); + + idx = alloc_slot(sc, n); + if (idx < 0) { + unlock(); + return 0; + } + g = ctx.active[sc]; + +success: + ctr = ctx.mmap_counter; + unlock(); + return enframe(g, idx, n, ctr); +} + +int is_allzero(void *p) +{ + struct meta *g = get_meta(p); + return g->sizeclass >= 48 || + get_stride(g) < UNIT*size_classes[g->sizeclass]; +} diff --git a/src/malloc/mallocng/malloc_usable_size.c b/src/malloc/mallocng/malloc_usable_size.c new file mode 100644 index 00000000..a440a4ea --- /dev/null +++ b/src/malloc/mallocng/malloc_usable_size.c @@ -0,0 +1,12 @@ +#include <stdlib.h> +#include "meta.h" + +size_t malloc_usable_size(void *p) +{ + struct meta *g = get_meta(p); + int idx = get_slot_index(p); + size_t stride = get_stride(g); + unsigned char *start = g->mem->storage + stride*idx; + unsigned char *end = start + stride - IB; + return get_nominal_size(p, end); +} diff --git a/src/malloc/mallocng/meta.h b/src/malloc/mallocng/meta.h new file mode 100644 index 00000000..61ec53f9 --- /dev/null +++ b/src/malloc/mallocng/meta.h @@ -0,0 +1,288 @@ +#ifndef MALLOC_META_H +#define MALLOC_META_H + +#include <stdint.h> +#include <errno.h> +#include <limits.h> +#include "glue.h" + +__attribute__((__visibility__("hidden"))) +extern const uint16_t size_classes[]; + +#define MMAP_THRESHOLD 131052 + +#define UNIT 16 +#define IB 4 + +struct group { + struct meta *meta; + unsigned char active_idx:5; + char pad[UNIT - sizeof(struct meta *) - 1]; + unsigned char storage[]; +}; + +struct meta { + struct meta *prev, *next; + struct group *mem; + volatile int avail_mask, freed_mask; + uintptr_t last_idx:5; + uintptr_t freeable:1; + uintptr_t sizeclass:6; + uintptr_t maplen:8*sizeof(uintptr_t)-12; +}; + +struct meta_area { + uint64_t check; + struct meta_area *next; + int nslots; + struct meta slots[]; +}; + +struct malloc_context { + uint64_t secret; +#ifndef PAGESIZE + size_t pagesize; +#endif + int init_done; + unsigned mmap_counter; + struct meta *free_meta_head; + struct meta *avail_meta; + size_t avail_meta_count, avail_meta_area_count, meta_alloc_shift; + struct meta_area *meta_area_head, *meta_area_tail; + unsigned char *avail_meta_areas; + struct meta *active[48]; + size_t usage_by_class[48]; + uint8_t unmap_seq[32], bounces[32]; + uint8_t seq; + uintptr_t brk; +}; + +__attribute__((__visibility__("hidden"))) +extern struct malloc_context ctx; + +#ifdef PAGESIZE +#define PGSZ PAGESIZE +#else +#define PGSZ ctx.pagesize +#endif + +__attribute__((__visibility__("hidden"))) +struct meta *alloc_meta(void); + +__attribute__((__visibility__("hidden"))) +int is_allzero(void *); + +static inline void queue(struct meta **phead, struct meta *m) +{ + assert(!m->next); + assert(!m->prev); + if (*phead) { + struct meta *head = *phead; + m->next = head; + m->prev = head->prev; + m->next->prev = m->prev->next = m; + } else { + m->prev = m->next = m; + *phead = m; + } +} + +static inline void dequeue(struct meta **phead, struct meta *m) +{ + if (m->next != m) { + m->prev->next = m->next; + m->next->prev = m->prev; + if (*phead == m) *phead = m->next; + } else { + *phead = 0; + } + m->prev = m->next = 0; +} + +static inline struct meta *dequeue_head(struct meta **phead) +{ + struct meta *m = *phead; + if (m) dequeue(phead, m); + return m; +} + +static inline void free_meta(struct meta *m) +{ + *m = (struct meta){0}; + queue(&ctx.free_meta_head, m); +} + +static inline uint32_t activate_group(struct meta *m) +{ + assert(!m->avail_mask); + uint32_t mask, act = (2u<<m->mem->active_idx)-1; + do mask = m->freed_mask; + while (a_cas(&m->freed_mask, mask, mask&~act)!=mask); + return m->avail_mask = mask & act; +} + +static inline int get_slot_index(const unsigned char *p) +{ + return p[-3] & 31; +} + +static inline struct meta *get_meta(const unsigned char *p) +{ + assert(!((uintptr_t)p & 15)); + int offset = *(const uint16_t *)(p - 2); + int index = get_slot_index(p); + if (p[-4]) { + assert(!offset); + offset = *(uint32_t *)(p - 8); + assert(offset > 0xffff); + } + const struct group *base = (const void *)(p - UNIT*offset - UNIT); + const struct meta *meta = base->meta; + assert(meta->mem == base); + assert(index <= meta->last_idx); + assert(!(meta->avail_mask & (1u<<index))); + assert(!(meta->freed_mask & (1u<<index))); + const struct meta_area *area = (void *)((uintptr_t)meta & -4096); + assert(area->check == ctx.secret); + if (meta->sizeclass < 48) { + assert(offset >= size_classes[meta->sizeclass]*index); + assert(offset < size_classes[meta->sizeclass]*(index+1)); + } else { + assert(meta->sizeclass == 63); + } + if (meta->maplen) { + assert(offset <= meta->maplen*4096UL/UNIT - 1); + } + return (struct meta *)meta; +} + +static inline size_t get_nominal_size(const unsigned char *p, const unsigned char *end) +{ + size_t reserved = p[-3] >> 5; + if (reserved >= 5) { + assert(reserved == 5); + reserved = *(const uint32_t *)(end-4); + assert(reserved >= 5); + assert(!end[-5]); + } + assert(reserved <= end-p); + assert(!*(end-reserved)); + // also check the slot's overflow byte + assert(!*end); + return end-reserved-p; +} + +static inline size_t get_stride(const struct meta *g) +{ + if (!g->last_idx && g->maplen) { + return g->maplen*4096UL - UNIT; + } else { + return UNIT*size_classes[g->sizeclass]; + } +} + +static inline void set_size(unsigned char *p, unsigned char *end, size_t n) +{ + int reserved = end-p-n; + if (reserved) end[-reserved] = 0; + if (reserved >= 5) { + *(uint32_t *)(end-4) = reserved; + end[-5] = 0; + reserved = 5; + } + p[-3] = (p[-3]&31) + (reserved<<5); +} + +static inline void *enframe(struct meta *g, int idx, size_t n, int ctr) +{ + size_t stride = get_stride(g); + size_t slack = (stride-IB-n)/UNIT; + unsigned char *p = g->mem->storage + stride*idx; + unsigned char *end = p+stride-IB; + // cycle offset within slot to increase interval to address + // reuse, facilitate trapping double-free. + int off = (p[-3] ? *(uint16_t *)(p-2) + 1 : ctr) & 255; + assert(!p[-4]); + if (off > slack) { + size_t m = slack; + m |= m>>1; m |= m>>2; m |= m>>4; + off &= m; + if (off > slack) off -= slack+1; + assert(off <= slack); + } + if (off) { + // store offset in unused header at offset zero + // if enframing at non-zero offset. + *(uint16_t *)(p-2) = off; + p[-3] = 7<<5; + p += UNIT*off; + // for nonzero offset there is no permanent check + // byte, so make one. + p[-4] = 0; + } + *(uint16_t *)(p-2) = (size_t)(p-g->mem->storage)/UNIT; + p[-3] = idx; + set_size(p, end, n); + return p; +} + +static inline int size_to_class(size_t n) +{ + n = (n+IB-1)>>4; + if (n<10) return n; + n++; + int i = (28-a_clz_32(n))*4 + 8; + if (n>size_classes[i+1]) i+=2; + if (n>size_classes[i]) i++; + return i; +} + +static inline int size_overflows(size_t n) +{ + if (n >= SIZE_MAX/2 - 4096) { + errno = ENOMEM; + return 1; + } + return 0; +} + +static inline void step_seq(void) +{ + if (ctx.seq==255) { + for (int i=0; i<32; i++) ctx.unmap_seq[i] = 0; + ctx.seq = 1; + } else { + ctx.seq++; + } +} + +static inline void record_seq(int sc) +{ + if (sc-7U < 32) ctx.unmap_seq[sc-7] = ctx.seq; +} + +static inline void account_bounce(int sc) +{ + if (sc-7U < 32) { + int seq = ctx.unmap_seq[sc-7]; + if (seq && ctx.seq-seq < 10) { + if (ctx.bounces[sc-7]+1 < 100) + ctx.bounces[sc-7]++; + else + ctx.bounces[sc-7] = 150; + } + } +} + +static inline void decay_bounces(int sc) +{ + if (sc-7U < 32 && ctx.bounces[sc-7]) + ctx.bounces[sc-7]--; +} + +static inline int is_bouncing(int sc) +{ + return (sc-7U < 32 && ctx.bounces[sc-7] >= 100); +} + +#endif diff --git a/src/malloc/mallocng/realloc.c b/src/malloc/mallocng/realloc.c new file mode 100644 index 00000000..18769f42 --- /dev/null +++ b/src/malloc/mallocng/realloc.c @@ -0,0 +1,51 @@ +#define _GNU_SOURCE +#include <stdlib.h> +#include <sys/mman.h> +#include <string.h> +#include "meta.h" + +void *realloc(void *p, size_t n) +{ + if (!p) return malloc(n); + if (size_overflows(n)) return 0; + + struct meta *g = get_meta(p); + int idx = get_slot_index(p); + size_t stride = get_stride(g); + unsigned char *start = g->mem->storage + stride*idx; + unsigned char *end = start + stride - IB; + size_t old_size = get_nominal_size(p, end); + size_t avail_size = end-(unsigned char *)p; + void *new; + + // only resize in-place if size class matches + if (n <= avail_size && n<MMAP_THRESHOLD + && size_to_class(n)+1 >= g->sizeclass) { + set_size(p, end, n); + return p; + } + + // use mremap if old and new size are both mmap-worthy + if (g->sizeclass>=48 && n>=MMAP_THRESHOLD) { + assert(g->sizeclass==63); + size_t base = (unsigned char *)p-start; + size_t needed = (n + base + UNIT + IB + 4095) & -4096; + new = g->maplen*4096UL == needed ? g->mem : + mremap(g->mem, g->maplen*4096UL, needed, MREMAP_MAYMOVE); + if (new!=MAP_FAILED) { + g->mem = new; + g->maplen = needed/4096; + p = g->mem->storage + base; + end = g->mem->storage + (needed - UNIT) - IB; + *end = 0; + set_size(p, end, n); + return p; + } + } + + new = malloc(n); + if (!new) return 0; + memcpy(new, p, n < old_size ? n : old_size); + free(p); + return new; +} |